RideFriends: More Rides, Fewer CarsJimMorris,CarnegieMellonSiliconValley

ABSTRACT

Let’sincreasethevehicleoccupancyratetoreducecongestion,pollution,andloneliness.ThisreportisadaptedfromanNSFproposalfromMorris,Resnick,Cranor,andSelker(Section2)andadesignforaridesharingservicecreatedinco‐operationwithmanyCarnegieMellonfacultyandstudents(Section3).

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TableofContents

1 VisionandReality ....................................................................................................................................12 Theory..........................................................................................................................................................22.1 IsthereaTippingPoint?............................................................................................................................... 32.1.1 Doessuccessincreaseexponentiallywithsubscribers? .............................................................................32.1.2 Howdosuccessfulpartnershipsaffectsubscribers’enthusiasm?..........................................................4

2.2 Howcanthenumberoffeasiblepartnershipsbeincreased?.......................................................... 52.2.1 Cancellphonesincreasethefeasibilityofpartnerships?...........................................................................52.2.2 Howcanwefindfeasiblematchesquickly?......................................................................................................6

2.3 Howcanpeoplebeinducedtorideshare?.............................................................................................. 82.3.1 RationalCosts.................................................................................................................................................................92.3.2 EmotionandRelationships ................................................................................................................................... 102.3.3 CultureandSymbols ................................................................................................................................................ 122.3.4 Demographics ............................................................................................................................................................. 122.3.5 PersonalityTypes...................................................................................................................................................... 13

3 DesignforaService .............................................................................................................................. 163.1 UserStories .....................................................................................................................................................163.1.1 CheriCarless................................................................................................................................................................ 163.1.2 LarryLanguageLearner ......................................................................................................................................... 173.1.3 HarryHitchhiker........................................................................................................................................................ 173.1.4 PatriciaParent ............................................................................................................................................................ 183.1.5 OprahOverachiever ................................................................................................................................................. 193.1.6 CamillaCommuter .................................................................................................................................................... 193.1.7 CharlieCarSwitcher................................................................................................................................................. 203.1.8 PeterParknride .......................................................................................................................................................... 203.1.9 OscarOperaLover..................................................................................................................................................... 213.1.10 ClaudeCommuter ................................................................................................................................................... 223.1.11 TomTaxidriver ........................................................................................................................................................ 233.1.12 CabCompanies......................................................................................................................................................... 233.1.13 Victor’sVanService ............................................................................................................................................... 24

3.2 NewTechnology ............................................................................................................................................243.3 UseCases ..........................................................................................................................................................253.3.1 Register.......................................................................................................................................................................... 253.3.2 Login(boring) ............................................................................................................................................................. 263.3.3 AdjustProfile(alotlikeRegister)...................................................................................................................... 263.3.4 GiveFeedback ............................................................................................................................................................. 263.3.5 OfferaRide................................................................................................................................................................... 273.3.6 AcceptaRider ............................................................................................................................................................. 273.3.7 CancelDrive ................................................................................................................................................................. 283.3.8 TakeaTrip.................................................................................................................................................................... 283.3.9 RequestaRide ............................................................................................................................................................ 293.3.10 AcceptaDriver ........................................................................................................................................................ 303.3.11 CancelRide ................................................................................................................................................................ 303.3.12 JoinaTrip(Seecase7) ......................................................................................................................................... 313.3.13 UseCase13:HandleEmergency(TBD) ........................................................................................................ 313.3.14 UseCase14:AnalyzeandManagePerformance(TBD)......................................................................... 31

3.4 NonfunctionalRequirements....................................................................................................................31

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3.4.1 Usability......................................................................................................................................................................... 313.4.2 Availability ................................................................................................................................................................... 323.4.3 Integrity ......................................................................................................................................................................... 323.4.4 Efficiency....................................................................................................................................................................... 323.4.5 Reliability ...................................................................................................................................................................... 323.4.6 Interoperability .......................................................................................................................................................... 323.4.7 Testability ..................................................................................................................................................................... 323.4.8 Robustness ................................................................................................................................................................... 333.4.9 Flexibility ...................................................................................................................................................................... 333.4.10 Maintainability......................................................................................................................................................... 333.4.11 Portability .................................................................................................................................................................. 333.4.12 Reusability ................................................................................................................................................................. 333.4.13 ExpectedArchitecturalTradeoffs.................................................................................................................... 333.4.14 HumanBackup,Legal,Political,OrganizationalIssues.......................................................................... 33

3.5 ProductRoadmap .........................................................................................................................................343.5.1 Learning......................................................................................................................................................................... 343.5.2 ConquertheSFBayArea........................................................................................................................................ 353.5.3 ConquertheUnitedStates..................................................................................................................................... 363.5.4 ConquertheWorld ................................................................................................................................................... 36

3.6 TheMatchingProcess..................................................................................................................................363.6.1 Karp’sAlgorithm........................................................................................................................................................ 37

4 Glossary .................................................................................................................................................... 395 References ..................................................................................................................................................1

1 Vision and Reality

Insteadofusingapersonalcar,apersonuseshercellphonetotravel.Sheentersherdestination;and,withinminutes,aproposalemployingoneormorevehiclesispresentedtoher.Thepick‐upoccurswithinminutesofherstarttime,nomatterhowsoonitis.Hertrip,alongwithpossibletransfersofvehicles,ismonitoredviaherphoneandphonesinthevehicles.Sheenjoysthecompanionshipbecausesheandherpartnershavearelationshipbeyondridesharing.Paymentandfeedbackarehandledgracefully.

TheRideFriendssystem(RF)employsacombinationofideasfrom511.org,GoogleTransit,Zipcar,Facebook,eBay,andeHarmony.Itexploitscellphonesandtheweb.Itisthecentralnervoussystemoftheentiresurfacetransportationsystemforaregion.Itlinksdriversandridersinanattempttomatchtheconvenienceofpersonalvehicles.Itcanbeaservicethathelpstheenvironment,improvesthequalityoflives,andsupportscommunity.Forananecdotalestimateofthevalueofridesharing,lookaroundyouwhiletravelingonanyroad.Theoccupancyrateisabout25%,basedonthenumberyoucanfitinacar.The102MAmericanswhodrivetoworksolopay21centspermileor$131Bperyearingasandmaintenance.Thesavingsfromtheirsharingmightfundabusiness.Ifthisprojectwerewildlysuccessfulitmightreduceone‐personcarsby50%insomeplaces.WhilethiswouldbehelpfulforpollutionandCO2reduction,itisnotasolutiontotheclimatechangeproblem.GettingChina,India,andotheraspiringcountriestochangetheirenergyproductionmethodsisessential.Theyarenotgoingtochangeuntiltheycanapproximateourwayoflife1;andCarlottaPerezobserved2,

Theold‘AmericanWayofLife’isstillseenasthemodelofwellbeingtoimitatebecauseithasnotbeenreplacedinAmerica.

Sothisprojectisasmuchaboutchangingattitudesandbehaviorasitisaboutreducingtraffic.Howdowemakecommunaldrivingsomethingpeopleeverywhereprefer?Thiskindofideahasbeentriedmanytimesandfailedbecausearobustmarketofdriversandridersneverformed.(IeventrieditatU.C.Berkeleyin1973!)Seedynamicridesharing.orgforalistofpast,present,andpotentialattempts.Whilethisvisionispossible.However,itisunlikelywithoutadvancesintwoareas:real‐timecontrolandhumanbehavior.Real­timecontrolofthousandsofmovingagents

Considerathousandormoreactivevehicletrajectories,definedbypredictedtimes,pointsonamap,andcapacities,andanotherthousandpotentialpassengersdefinedbytimes,startpoints,andendpoints.Therearealsoseveralhundred“wildcard”vehicles,e.g.taxisthatcanbeassignedarbitrarytrajectories.RFassignseachridertooneormorevehicleswhosetrajectorieswillcarryherfromstarttoend,allowingforreasonablewaitsatpick‐uplocations.Thevehiclesreporttheirpositioneveryfewminutes,causingthepredictionstobeupdated.Eachparticipantissenta“timeandplacetorendezvousmessage”atsuitableintervals.CongestionthroughouttheregionismonitoredandRFrevisespredictedarrivaltimescontinually.Vehiclesarere‐routed,andplansarechangeddependably.Theperformanceofindividuals,fleets,andRFitselfisimprovedusingthedataexhaustfromoperations.Changinghumanpreferencesandhabits

AsBowlingAlone3andotherresearchshows,evenifwecreateasystemthatapproachesthe

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convenienceofapersonalcar,peoplehavemanyotherreasonsfordrivingalone.Thereisuncertainty,fear,andthedesireforsolitudeorcontrol.Incertaintimesandplacescarpooling,hitchhiking,andridesharingarecommon.4Weneedtoexplainthisbehaviortounderstandhowtopromoteittodayinmanyplaces.

2 Theory

Figure1.RideFriends’sPipeline

Figure1showsthecrucialpipelineofRF.ApersonenterstheserviceasaSubscriber.HerlevelofEnthusiasmdetermineshowoftensheproposesgivingorreceivingaride,therebybecomingaProposer.TheservicematchesproposingdriversandridersfortimeandlocationFeasibilityandoffersvariouspartnershipstoher,makingheraDecider.SheacceptsapartnershipbasedonitsCompatibilitywithherneeds,andthenbecomesaPartner,someonewhoactuallyparticipatesinaride.Compatibilityisbasedupontwopersonalattributes,herperceivedCostofthetripandherRelationshipwiththeproposedpartners.Finally,beingasuccessfulPartnerincreasesherEnthusiasm,sothemodelhasapositivefeedbackloop.Theredboxesidentifywhichofthefollowingthreesectionsdescribethecomponentsandtheirinteractions.

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2.1 Is there a Tipping Point?

Ridesharingcansucceedonlyifthereareenoughridersanddrivers.Thedensityofuserstravelingsimilarroutesmustbehighformatchingtooccur.Ifthereisnotippingpointatwhichaserviceattractsaself‐sustainingcriticalmass,itisnotgoingtosucceed.Thefeasibilityforridesharingcanbeestimatedforaregion,corridor,oranemployerhubusinginformationfromplanningdatamaintainedbythemetropolitanplanningorganizationsoremployers.Theirdatabasesarebasedonhouseholdactivityandtravelsurveys.Theinformationincludesorigin/destinationflowsbytimeofdaybyvariousmodes,distributionsoftrippurposes,aswellasdemographicinformation.Thiswillallowustoobtainupperlimitsofpotentialridesharers,byagegroupsorotherdemographics,aswellasorigin/destinationareas.Generally,analystshaveaskedthequestionofhowmanypeopleinawholeregionmightrideshare.Weareaskingacomplementaryquestion:howbigdoesagroupofwillingridesharersneedtobeinordertoself‐sustain.Aridesharingsystem,likeamarket, becomesself‐sustainingwhenmorepeoplearejoiningandparticipatingthandroppingout.Oneneedsamodelthatestimateswherethetippingpointis,therebypredictingthecostandtimingofarecruitmentcampaign.Apreliminarysearchoftheeconomicsliteraturehasnotfoundanytheoryofhownewmarketsgrow,onlyhowtheyreachequilibrium.5

2.1.1 Does success increase exponentially with subscribers? AveryusefulpaperbyHallandQuershe6proposedamodelfortheeffectofmutualcompatibility.SupposethenumberoffeasibledriversforagivenriderisPoissondistributedwithmeanN.LetPbetheprobabilitythatoneofthosedriversiscompatiblewiththerider.Thentheprobabilitythattherideractuallygetsarideis1‐e‐PN.Figure2showshowtheprobabilityofsuccessdependsuponPandN;e.g.,ifthereare20driverseachwith0.20probabilityofsaying“yes”,theriderhasabetterthan80%chanceofgettingaride.RaisingeitherNto50orPto0.35makestheotherparameterirrelevant.Atthislevelofabstraction,thesamereasoningappliesifweaskthequestionwhetheragivendrivercanfindapartneramongNriders.

TheauthorswentontomeasurePforsubscriberstoarealsystem,LosAngelesSmartTraveler.7Theresponsesofdriverscalledwitharider’srequestwas

Yes 9%Maybe 11%NotToday 28%No 16%NoAnswer 36%.

Sadly,theSmartTravelersystemarbitrarilylimitedthenumberofdriversapproachedto10whileFigure2suggeststhatcalling20ormorewouldhavesignificantlyimprovedperformance.Also,thisstudywaspublishedin1997,beforewidespreadcellphoneuse,sothe“NoAnswer”categorymightbesmallernow.

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Figure2.EffectofPandNonSuccessfulPartnering

2.1.2 How do successful partnerships affect subscribers’ enthusiasm?

Figure3.EffectofSuccessonSubscribers’Enthusiasmover25Days

Considerarangeofsubscriberpopulationsfrom200to600.Supposeeachperson’senthusiasmstartsat20%,theprobabilityofmakingaproposaleachday.Ifaproposalsucceeds,sheincreasesherenthusiasmbymovingtheprobabilityhalfthedistanceto1.0.Iftheproposalfails,shehalvestheprobability.Asenthusiasmincreases,thenumberof

P0.00

P0.06

P0.12

P0.18

P0.24

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P0.36

P0.42

P0.48

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ProbabilityofaPartnership

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proposersincreases,thenumberoffeasiblepartnersincreases,andtheprobabilityofaproposalsucceedingincreases,accordingtotheexponentialformulaabove.Thiscausesenthusiasmtoincreasefurther—apositivefeedbackloop.

Forthisexample,asubscriberpopulationof400issufficientforasustainedgrowthrateofproposersevenifPisjust0.01toaccountforthelowprobabilityoftwosubscribersbeingbothfeasibleandcompatible.Onthefirstday80ofthe400propose,then80*(1‐e‐0.8)=44findpartners.The44increasetheirenthusiasmfrom20%to60%,thedisappointed36decreasetheirenthusiasmto10%,andthe320whodidn’tproposeremainat20%.Onthenextday44*0.6+320*0.2+36*0.1=94propose,andthenumberofproposerscontinuetoincreaseeachday.Thisisastrawmantheory.Measurementofrealmarketsystemsisneededtofindadependabletheory.Thesystemneedn’tbearidesharingservice;wecanuseanynascentserviceinwhichthereare“buyers”and“sellers”whomakemoredealsasthesizeofthemarketincreases.Ifthereisapowerfulpositivefeedbackeffect,thenaservicethatachievescriticalmassalsohasthechanceofmonopolizingaregionalmarket.

2.2 How can the number of feasible partnerships be increased?

RealdatacollectedinEasternMassachusettsconsideredtwopeopletobefeasiblepartnersiftheirsourceanddestinationarewithinamileandstarttimesarewithinthirtyminutesofeachother.Itshowedthat60%ofmorningcommutershadafeasiblematch.8Apparently,thatwasnotenough.20

2.2.1 Can cell phones increase the feasibility of partnerships?

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Figure4.TheDispersalofSourcesandDestinationsforCommuters

Traditionalcarpoolsaredifficulttosetupandreduceone’stravelflexibility.Theinternetandcellphonescangreatlyexpandtheoptionsandconvenience.Aconcoctedexample,depictedinFigure4,suggestshowhubscanincreasethenumberoffeasiblematches.Supposethereare1,000driversstartingfromtendifferenthomeneighborhoodsandgoingtotwentydifferentcompanies.Forsimplicity,assumetheyareequallydistributedamongneighborhoodsandcompanies,100ineachneighborhood,50ineachcompany.Onaveragethereareabout5peopleinatypicalneighborhoodXwhoarealsodrivingtocompanyY.Sothereareabout5feasiblepartnersforsomeoneseekingaride.Ifthebasicprobabilityofcompatibilitybetweenrideranddriveris0.1,thenthechanceofapartnershipisabout0.4.Ontheotherhand,supposewehaveanintermediatehubthatall1,000commuterspassthroughataboutthesametime,allowingpassengerstoswitchfromsomeonefromtheirneighborhoodtosomeonegoingtotheircompany.Inthiscasethereareabout100peopletheridercanstartwithandabout50hecancontinuewith.Thenumberoffeasibletripshasincreasedbymorethanafactorof10andtheprobabilityofsuccessgoesupto1(=0.993)!Generally,ifthereareDdrivers,Nneighborhoods,andCcompanies,thepotentialnumberofdriversforagivenriderisaboutD/max(N,C)iftransfersareallowedandD/NCiftheyarenot.Soahubhasadramaticeffect.Inmostregionstherearefewlargehubsperse,butmajorhighwaysandbridgesconstitutevirtualhubs.Forexample,theSanFranciscoBayArea’sUS101isasortof40‐milehubrunningfromSanFranciscotoSiliconValley;itisfedbyhundredsofneighborhoodsanddrainedbyhundredsofcompanies.Transferscouldoccuranywherealongthathighway.Thisiswherecellphonesbecomecrucial.Arrangingtherendezvouswithoutthemwouldbeunthinkable.However,ifthetwodriverscanbeincommunication,thenadjustmentsfortrafficandconfusioncanbemade.Themethodofrendezvouswillhavetobeverycarefullydesignedandtestedtomakethisidearealistic.

2.2.2 How can we find feasible matches quickly? Webelievethatamoderncomputersystem(i.e.clustersofprocessorsaccessingcommondiskdata)canfindfeasiblematchesandcanfunctioninreal‐timeforthousandsofpeopleperminute.Wewillexploretwoapproaches:findanduseasuitablemovingobjectdatabasesystem9(MOD)orbuildaspecial‐purposematcher.2.2.2.1 Using a Moving Object Database ThereareseveralMOD’sunderdevelopment.Ifonesperformanceisacceptable,usingitmightsavesignificantworksinceitwouldprovidemanyconvenientfeaturesliketransactionsanddataintegrity.Whenadriverproposes,RFusestheMOD,whichholdsanetworkoftheregion’stransportsystem,tosuggestashortestroutefromstarttofinish,allowthedrivertomodify,andentertheresultingrouteintoitsMOD.

Whenariderproposes,RFfirstqueriestheMODforthebestroutefortherider,i.e.oneshewouldtakeifshedroveherself.RFqueriestheMODfordriver’sroutesthatpassthroughtherider’sstartandfinishlocationattheappropriatetimes,usingtheriders’bestroutetoboundthepossibilitiesat,say25%longerthantherider’sbest.Ifareasonablenumber,saytwenty,arefound,theroutesarepassedontothenextphasesthateventuallysuggestthemtothepotential

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partners.IftheMODdoesnotfindenoughroutes,RFaskstheMODfor(a)driver’sroutesthatpassthroughtherider’sstartlocationatanappropriatetimeand(b)driver’sroutesthatpassthroughtherider’sendlocationatalatertime.Thenitasksforintersectionsinspace‐timebetweenpairsofroutesfromaandb.Ifthisfails,itcansearchforroutesinvolvingthreedrivers.Wedon’tknowofanavailableMODthatwillsupporttheseoperationsandperformwell,butwillattempttofindoneorcollaboratewithagroupthatisworkingonone.2.2.2.2 Using a special-purpose matcher TheneedsofRFmightbebetterservedbyatailor‐madematchingsystem.Hereisasketchofhowwewouldbuildone:Thedatastructureisadirectedgraphwhereeachvertexrepresentsanintersectionofstreets,freeways,orraillines.Edgesrepresentplannedtravelbyadriver,bus,train,orothervehicle.Eachedgeislabeledwithitsarrivaltimeatitsstartingvertex,distancetotheendingvertex,thedriver,andthepredictedspeedofthedriveronthisedge.Everypairofvertexeswithapassagebetweenthemalwayshasthreeedgesrepresentingthechoicesofdrivingalone,walking,andataxiride,withanarrivaltimesignifyingthattravelcanbeginimmediately.Fromthedriver’sprice,therider’swaitingtime,andtherider’svalueoftime,onecancomputethecosttotheriderfortraversingtheedge.Plausiblepricesare0forwalking,$0.50/milefordrivingalone,$2.50/milefortaxi,$.25/mileforridingwithafriend,etc.Train,bus,andvanschargetheirstandardfares.Therider’svalueoftimevaries,but$1/minuteisaguessforacommuter,i.e.waitingforfiveminutescoststherider$5,walkingamilecosts$20.Whenadriverproposes,RFinsertsherchosenroutebyaddingtotheedgelistateveryvertexalongtheroute.Whenariderproposes,itfindsmatchesbyperformingacheapestpathsearchinthegraph.Thecheapestpathisnotusuallytheshortest,whichislikelytobeadirecttaxirideoraverylongwalk.TofindcheappathswewilluseashortestpathalgorithmsuggestedbyKarpthatutilizesas‐the‐crow‐flieslowerbounds,forwardandbackwardsearches,andanupper‐boundofabout125%oftheshortestpathtofindabouttwentyfeasiblepaths.10Thepathsmayinvolveswitchesamongdrivers,butthealgorithmshouldprefercontinuingwiththesamedriverbecauseswitchingvehicleswillinvolveawaitthataddstotherider’scost.RFneedsinformationabouttraffic.Itcanobtainitfrompublicsourcesorreportsfromactivetravelers,asdidtheserviceDashExpress.11Theinformationcanbeusedforbothpredictionofgeneralcongestionpatternsandreal‐timecontrol.Historywillbeusedtoinitializethespeedcomponentofedgesastheyareaddedtothegraph.Asthetimeassociatedwiththeedgeapproachesthepresent,currentinformationwillbeusedtoadjustthespeedcomponent,possiblyusingmodelstopredictcongestionpatternsthatmovedownahighway.RFwillre‐computearrivaltimestodetectbreakdownsinrendezvousplansandtakecorrectiveaction.Performingthesecomputationsformanyusersinreal‐timepresentsachallenge.ThefirststepinthisresearchistotryasimplealgorithmonalargevolumeofrealtripdataandcompareitsperformancewithmoregeneralMODproducts.12

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2.3 How can people be induced to rideshare?

Virtuallyallanalystsofridesharingagreethathumanpreferencesaretheprimaryobstacletosuccess.Whydosomanyofusdrivealone?Table1listssomereasonsandpossiblewaysofmitigatingthem.

DrivingAloneAdvantage Mitigation

Plan‐freetravel:Wehaveourcarwithusallthetime,canstartatripanytimeandchangeplansanytime.

Quickschedulingwithcellphone

Easyre‐scheduling.Criticalmassofsubscribers.

Reliability:Yourcaritisalwaysavailable.Carpools,taxis,orotherservicesarenot.

Maintenanceofahighly‐disciplinedsocialnetworkRendezvouspredictionCriticalmassofsubscribers

Safety:Therearebaddriversandbadpeople. Vettingofsubscribers,includingdrivingrecords.PartnerfeedbackReal‐timemonitoringofcontacts.Need‐to‐knowdisclosureofpersonalinformation

Control RendezvouspredictionDiscoveryandhonoringofpersonalpreferences

Status:Carsarelikejewelryformen.13 PositiveincentivesforsharingUpscaleimage

Asociality:Manypeopleprefersometimestobealone,orfindthehabitsofsomeotherpeopledistasteful.14

PositiveincentivesforsharingMatchingpersonalpreferencesEasywithdrawalfromcommitments

Habit:Foracentury,Americanshavedrivencarsandbecomecomfortablewiththesystem.

Low‐commitmentwaystotrynewhabits.

Table1.WhyDrivingAloneisPreferred

Overtheyears,avarietyofapproacheshavebeenproposedtoestimatethenumberofpeoplewhowouldgiveupsolodrivinginfavorofridesharing.615Somewerefromtheperspectiveofridesharingunitformation,andincludedassessingareawidemaximumpotentialbyestimatingpossiblematchesandidentifyingcharacteristicsofpeoplewhowouldsharerides.Anothersetofestimationmethodscenteredondecisionapproachesandincludedutilitymaximization,

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simulationmodels,andgames.Stillanotherapproachuseddemand/supplyrelationshipsintrafficequilibriumflows,toestimatetheeffectsofhighoccupancyvehiclelanes.Theapproachescanbecategorizedroughlyintothreeareas:

• RationalChoice:Itincludespredictability,timeurgency,andcontrolversusphysiological,psychological,andbehavioralpenalties.

• EmotionalChoice:Thiscategoryiscrystallizedwiththetheoryofplannedbehavior16,claimingthatpeoplemaketheirdecisionswiththecombinationofattitude,subjectivenorms,andperceivedbehavioralcontrol.

• Habit:Evenifachangeisjustified,peopleoftenactthesamewaytheydidbefore.1718Mostoftheinvestigators—probablyattunedtoenvironmentalconcernsandthemselvesprosocial—seemtohopeforpositiveattitudesaboutridesharing,butareusuallydisappointed.19Refreshingly,apaperbyOry15facesreality:peoplehaveadaptedtotheirdrivingroutine,aregenerallysatisfiedwithit,andmayevenlikeit.Unlessthecostsbecomeexorbitant,thenegativeaspectsofdrivingalonearenotpowerfulenoughtobringaboutchange.Webelievethewaystochangebehaviorare

• Rational:Reducethedifferenceinconvenienceandreliabilitybetweendrivingaloneandridesharingtoanacceptablelevel.

• Emotional:Discoverandpromotepositive,experientialinducementsforridesharing.• Cultural:Exploitandpromotethecurrentimpulsefavoringsustainabilityandclimate

protection.

Weformalizethefirsttwoapproachesascostandrelationships.Theprobabilitythattwodeciders(i.e.afeasiblerider‐driverpair)arecompatibleforagiventripismadeupofthesecomponents:C,thecostsandR,therelationship.Theculturalapproachdoesn’tapplyimmediatelytotheoperationofRF,butsupportsincreasesandretentionofsubscribers.

CompatibilitymightbeproportionaltoR/C.Ontheotherhand,thesetwocomponentsmightnottradeoffagainsteachotherinasimpleway;i.e.agreatorterriblerelationshiptrumpscostsandanexorbitantcosttrumpsaneutralrelationship.Thisquestionwillbeinvestigated.

2.3.1 Rational Costs Section2.1and2.2presentedideasforreducingcost,butdidnotaddressthesubscribers’perceptionandopinionsaboutcost.Anyservicemusthaveafirmgriponservicequalitymetrics.Thesequalitymetricsareout‐of‐pocketcost,meantraveltime,traveltimevariance,andlead‐timeforarranging.Theutilitycurvesforeachoftheitemsareunknown,butweguesstheywouldbesuper‐linear.Thecostfunctionmaynotbeadditive;theremaybea“dealbreaker”thresholdforeachone.20

o Chargingtoshareout‐of‐pocketcostsisfine;muchmoreisnot.o Increasingtraveltimebylessthan10%isnotnoticed.o Increasingtraveltimebymorethan30%isunacceptable.o Waitingismorefrustratingthanmovingslowly.o Lunchhourtimeismorevaluablethancommutingtime.

Someothercost‐relatedquestions:o Whatistheeffectofowningacar?o Whatisthetradeoffbetweenprobabilityofgettingamatchandtheeffortrequiredto

announcetripsormonitorforanswers?

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o Wouldsubscribersbecomfortablewithanauctionsystem?21o Howmuchwouldsubscriberspaytheserviceitself,andwhatcombinationofsubscription

costsandper‐tripfeesisappropriate?

Foreachofthesequestions,eachdemographicgroupwillhaveadistributionoverpeople,sincepreferencesdiffer.Simplesurveyswillnotbeusefulindiscoveringabehavioralcostfunction.Weplantomeasurebehaviorinvivothroughanovelpreferenceelicitationmethod.IndividualswilluseaGPS‐enabledcell‐phoneapplicationtotracktheirownmovements.Aweb‐basedapplicationwillthenpromptthemtoreflectonparticulartransportationincidentsfromthepreviousweek,answeringquestionsabouthowfarinadvancethetripwasplanned,andhowacceptablevariousalternativetransportationmodeswouldhavebeen.Wehaveusedarelatedtechniquebeforeinadifferentrealm,elicitingprivacypreferences.22

Figure5.AWorldWarIIExhortation

2.3.2 Emotion and Relationships WebelievetheapproachrepresentedbyFigure5—appealingtopatriotism,socialconscience,orguilt—isineffectivenow,evenifitoncewas.Infact,carpoolinghasbeendecliningsteadilyforthepastfortyyears.23Asanyparentlearns,offeringexciting,newexperiencescanbeasuperiorwaytomotivatepeople.Ridesharingcanbealifeenhancer.Manypeoplemightrespondtowhatitoffers:richerexperienceswithpeopleandbetteruseoftraveltime.Whilethisthesisisnotobvious,experienceandmuchresearchhasprovedthatthenegativeaspectsofdrivingaloneare

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insufficienttochangebehaviorpermanently.Furthermore,webelievethatfindingwaystomaketraveltimemoreproductiveandpleasantshouldbefoundintherelationshipamongthetravelers.Anecdotessuggestthatgoodrelationshipsareoneofthemostvaluableoutcomesofridesharing,buttheyareusuallyserendipitous.CanwepredictgoodrelationshipsthewayeHarmonyetal.claimto?Ifwefindthatdifferentdemographicshavedistinctlydifferentsocialneedsanddesires,thenpromotingdistinctservicesmayleadtobetterresults.2.3.2.1 How is relationship measured? Somehavesuggesteddegreesofseparationshouldbeconsidered,e.g.R=1/2swheres=0ifwearefriends,s=1ifwehaveafriendincommon,etc.Thesecanbegleanedfromsocialnetworkingsitestowhichsubscribersbelong.Anorthogonalmeasureiscommondeclaredinterests,e.g.countrymusic.Thesecanbediscoveredfromaquestionnairelikethoseofdatingservices,butfocusedonthelessintimatequestions;e.g.“Doyouliketotalkwhiledriving?”Aswithcosts,theinteractionoftheseaspectsinnotwellunderstood.Wewillconductstudiesofdifferentdemographicstoassessrelationshipprediction.Ourtargeted,personalscenariosrelatedtotheiractualprevioustripswillprobeforthevalueofrideswithpeoplewithvariouskindsofrelationships(e.g.,aboss,aco‐worker,afellowwineenthusiast,oranativespeakerofaforeignlanguageoneisstudying)2.3.2.2 Personal Safety Oneofthereasonspeopledon'tcarpoolorhitchhikeistheawkwardnessofdealingwithstrangers.Thismakesserviceswithprofessionaldriverspreferableformanypeople.However,wecandoafewthingstomitigatethenaturallackoftrust.

• AllparticipantsareregisteredwithRF,anddriversgetmorevettingintheformoflicenses,drivingrecords,financialinformation,etc.Participantsareencouragedtoincludepicturesandpersonalinformationbuthavetheoptionofrestrictinginformation.TheservicemightbedoneasaFacebookapplication.

• Forthewary,onlytheinformationnecessarytocarryoutadrivingtransactionneedbegiventoparticipantsbythesystem.Paymentstodriverscomethroughthesystemlikecash.

• Cellphonesfacilitatetherendezvousbykeepingpartiesawareofeachother'slocation,possiblysignalingwhenline‐of‐sightisestablished.

• Participants,uponmeeting,authenticateeachotherusingBluetoothcellphonesequippedwithsecure,privacy‐sensitivesoftware.

• Thephonesrecordtheproximityofparticipantsforpurposesofbillingandcomplaintdocumentation.

• Anyparticipantcancallforpoliceassistanceviatheircellphoneduringaride.• Ideally,allcellphoneswouldbeequippedwithtwostandardbuttons:"Help!"and"Interesting!"

• Thefirstwouldbea911callthatneedednovoiceinteraction,i.e.itwouldsimplyreadascripttowhoeveranswers,saying"IamXXXlocatedatYYY(,movingZZZatAAAmph).Irequireimmediate,emergencyassistance."

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• Thesecondwouldrecordthetimeandplacealongwiththelast(!)5secondsandnext5secondsofsound.Itcanbeusedforavarietyofpurposes:takingnotes,alertingfriendstocoolthings,warningothersofadangerinthearea,etc.

• ThesystemmaintainsaneBay‐likereputationsystemtowhichdriversandriderscanreportwithoutfearofreprisals.

2.3.3 Culture and Symbols AutomobilesareimbeddedinAmerica’sculture,andbusinessesthatdependuponculturalchangeusuallyfail.24Untilwecanofferhopethatchangeispossible,therewillnotbesignificantinvestmentinridesharing.ThechangeinAmericansmokinghabitsillustratethatchangeispossibleoveranextendedperiod.Asidefromtheextensiveinfrastructurethatsupportsdrivers,therearepowerfulsymbolicvaluesincarownershipanduse.25AcarpermitsthefreedomandpowerthatrepresentAmericatomanypeople.Infact,differenttypesofautomobiles,ranginginpricefrom$10,000to$440,000,canbeusedtorepresentthespecificvaluesandaspirationsoftheirdrivers:economy(ChevroletAveo),wealth(Porsche),safety(Volvo),reliability(Toyota),Greenness(Prius).Inacarculture,likeCalifornia’s,thekindofcaronedriveshelpsdefineone’sstatusandvalueswhileinvitingotherstoappreciateandperhapsemulatethem.Hybridsmightbemorecostlytodrivethansomecoventional,smallcars,butarepreferredbecausetheysay“I’mgreen,”not“I’mpoor.”ThePrius’sdistinctivebodystylemighthavemadeitpreferabletotheHondaCivichybrid,buttheHondaInsight’sstrangestyledidn’tovercomeitspracticalshortcomings.

Thecellphoneisbecominganotherobjectthroughwhichpeoplecanexpresstheirvalues.Thephonesbrand,color,andwhatappearsaphonesdisplaycanbeexpressive.26RFmustofferitssubscriberswaystoexpresstheirvalues.

2.3.4 Demographics Specificgroupsmightdemonstratesignificantlydifferentattitudesaboutridesharing.Inoursurveysandbehaviorstudiesweshallcomparethetraitsofseveralofthefollowingdemographics.Thiswillbeespeciallyimportantinunderstandtheroleofrelationshipopportunitiesaswellasacceptablecostranges.2.3.4.1 Millennials InBowlingAlone,Putnamobservessignificantvariationinsocialcapitalbetweengenerations.Somebelievethatthegenerationbornbetween1985and2005mightbemoreprosocialthanearlierones.27Youngpeoplecontemplatingbuyingtheirfirstcarmighthaveverydifferentcostfunctionsfromoldersuburbanites.Wewillexplorethedecision‐makingprocessforbuyingone’sfirstcar.2.3.4.2 Co-workers Astudy21showsthatridesharingprogramsrestrictedtocompaniesaremoresuccessful.Foralargecompanyco‐workerssharealocationandareasonablelevelofsocialcapital.Theyeitherknowpotentialpartnersorareopentomeetingco‐workers.Aprogramoflowerlevelworkersoccasionallypartneringwithexecutivesmightincreasethesocialcapitalofthebusiness.2.3.4.3 Ticket Holders Peopleattendingentertainmentandsportseventsshareanarrowtimewindow,aparkingproblem,andacommoninterest.Aretheymorelikelythancommuterstobeinasocialmood?

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Aretheymorewillingtosharearideonceratherthancommittingtocarpooltowork?2.3.4.4 Students Manysubjectsandskillscanbelearnedandpracticedorally.Studentsatthesameschoolsharenarrowtimewindows,interests,andsociallife.Whatsubjectsandinterestsarebesttopracticeorally,e.g.foreignlanguages?2.3.4.5 Patients Peoplewithperiodicdoctor’svisits,e.g.chemotherapypatients,mightsharerides.Couldridesharingenhancethehealth‐relatedsocialnetworksalreadyontheinternet?Isinformationoremotionalsupportmorevalued?2.3.4.6 Parents Manyparentsfindthemselveschauffeuringtheirchildrenformanyhoursaweek.Often,theyarrangewithotherparentstodrivebutthesearrangementstaketimetosetupandchangewitheachyear.Howdoattitudeschangewiththechildren’sages?2.3.4.7 Singles ThecurrentgenerationuseseHarmony.com,Match.com,Jdate.com,etc.withoutreservation.Wouldsinglepeoplelookonridesharingasanopportunityforrelationshipexplorationorascreepy?

2.3.5 Personality Types Peopledifferinwaysthatarenotcapturedbydemographics.Therearemanyframeworksforparsingthedifferences,anditmaybeusefultoconsiderthemwhenconsideringmotivations.Unlikedemographicstheseframeworksmightalsohintathowpeoplemightbepairedbasedondifferences.Thefollowingtablessummarizeshowthevarioustypesmightperceivetheirchoices.

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Dichotomies Preferences DrivingAlone

DrivingOthers

Riding

Extraversion…theouterworld?

Communicating Favoriteworld:Doyouprefertofocuson…

Introversion…yourowninnerworld?

Solitude

Sensing…focusonthebasicinformationyoutakein?

Information:Doyoupreferto…

Intuition…interpretandaddmeaning?

Thinking…logicandconsistency?

SavingTime

EconomyGreenness

EconomyGreennessEase

Decisions:Whenmakingdecisions,doyouprefertofirstlookat…

Feeling…thepeopleandspecialcircumstances?

Safety RelationshipsControl

Relationships

Judging…getthingsdecided?

Structure:Indealingwiththeoutsideworld,doyoupreferto…

Perceiving…stayopentonewinformationandoptions?

Noplanningneeded

Table2.TheMyers­BriggsFramework28

TheVALS29systemputsbuyersintoeightcategories,basedonthreeprimarymotivations—ideals,achievement,andself‐expression—thatareenduringandtranscendage,gender,income,andgeography.Thecategoriesarefurtherrefinedbyameasureofresources.ThemostpromisingdemographictorecruittoRFareyoungercitydwellerswhomightbemoreecologicallyandcommunallymindedthantheireldersandwithoutcars.TheyoungestVALSgroup,Experiencers,aretrendsetters,earlyadoptersoftechnology,andgenerallycollegestudentsorgraduates.Theyseemlikethebestgrouptostartwith,probablywhentheyareincollege.Thenextyoungestgroup,Strivers,areinfluencedbyadvertisingandpeers,somightbebroughtalongifatrenddevelops.Ratherthanreachforafull‐blowndriver/ridermarket,itmightbebettertostartbyservingriderswithasystemthatknitstogetherpublictransitandtaxis.Oncealargecommunityofridersisassembled,civiliandriversaremoreeasilyrecruitedsincetheywillfindriderseasily.ThebestwaytorecruittaxiandlimodriversistoprovideRFservicewithGPSnavigatorswhichtheypurchase.Tomaximizethepotentialriderpopulationtheprimaryinterfaceshouldbealow‐endcellphonedrivenbyvoicecommands.Locationservicesmightbeobtainedfromcellphonecarriers.

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Motivationto…

Primary

Motivation Motivationand

Resources%ofUS

Age

DriveAlone DriveOthers Ride

Innovators 10 44 Flexibility Curiosity CuriosityThinkersfollowideasandprinciples.

11 56 Solitude Greenness Greenness

Ideals

Believersfollowbeliefsandprinciples.

16.5 52 Independence CommunityGreennessGenerosity

CommunityGreenness

Acheiversseeksuccessandcontrol.

14 41 ControlTime

Control

Acheive

ment

Striversseekapprovalandmoney.

11.5 29 Status GreennessEconomy

GreennessEconomy

Experiencersseekexcitementandvariety.

13 25 Movingandcontrolling

Movingandcontrolling

Meetpeople

Self­

expression

Makersacttoimpactthephysicalworld.

12 46 Carasself Carasself

Survival 12 70 Isolation EconomySafety

Table2.TheVALS™Framework

Aventurecapitalistweknowsays,“AlwayscreateproductsthatfacilitatesometheDeadlySins.”ThesesinsaresometimesassociatedwiththenineEnneagramtypes.

Type DriveAlone DriveOthers Ride1.Reformer,Critic,PerfectionistSin:Anger

Norestraintonroadrage.

Back‐upfortraffic‐inducedconfrontations.Self‐righteousgreenness

Self‐righteousgreenness

2.Helper,Giver,CaretakerSin:Pride

Showoffcar’sexterior.

Serveriders.Showoffinterior.Begreenerthanothers.

Begreenerthanothers.

3.Achiever,Performer,SucceederSin:Deceit

Usecartorepresentself.

Control

4.Romantic,Individualist,ArtistSin:Envy

5.Observer,Thinker,InvestigatorSin:Avarice

Savetime. Savemoney.Getrewards.

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6.Loyalist,Devil'sAdvocate,DefenderSin:Fear

Safety

7.Enthusiast,Adventurer,MaterialistSin:Gluttony

Meetnewpeople.

8.Leader,Protector,ChallengerSin:Lust

Control Control

9.Mediator,Peacemaker,PreservationistSin:Sloth

Nocommitmentstokeep.

SleepLessresponsibility

Table4.EnneagramTypes30

3 Design for a Service Thissectioncoversmanyaspectsofthedesignforarealservice.Abusinessanalysisisalsoavailable.31

3.1 User Stories

3.1.1 Cheri Carless ShelivesSouthofMissionandworksinSanFranciscoasaninsuranceadjuster,doesn'townacar,usestheMunitogettoworkanmostotherthings.Sheistwenty‐eight,single,straightandlookingforaseriousboyfriend.HerproblemisgettingaroundtheBayAreaorgettinghomelateatnight.Sheusedtosolvesuchproblemsbydependingonfriends,takingtaxis,andrentingcars.

• ShegoestotheRFwebinterfacefromherhomecomputerwhenshewantstovisitafriendinSantaCruzonaSaturday.Shemustregisterbeforelookingforrides.ThemainrequirementisthatshehasapersonalcellphonethatcanbeverifiedbyRF.Shecanfillinlotsofpersonalinformationalongwithprivacyruleslater.

• RFgetstheavailabilityandpricesfromrentalagenciesandZipcar.Italsofindssomevanservicesandcommuters.Thealternativesitsuggestsare

o AnanonymouspersonisdrivingtoSantaCruzfromSFSaturday,willtakeheralongforgasmoney($40),butisreturninglaterthanshewanted.1.5hrs.traveltimeeachway

o Zipcar,$68fortheday,gas,parking&insuranceincluded,1.5hrstraveltimeeachway

o MunitoCivicCenter,AlamoRentalforday($40),Gas($40),MuniHome,1.7hrstraveltimeeachway

o Muni/GreyhoundBus/Taxi,,3.2hreachway(shorteningstayinSC),$30o Bart,Caltrain,andBus,$23,3.5hrstraveltimeeachway

• Cheridoesn'tfeellikemeetinganyoneornegotiatinghisorherpricedown,sosheoptsforZipcar,whichshe'salreadyregisteredfor.

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• ShemakesthereservationthroughRFwhichchargesZipcar$2.• Onthetrip,CheriputsherGPS‐equippedcellphoneonthedashboardanditsupplies

navigationhelpviaherBluetoothearpiece.ItalsosendsoccasionalmessagestoRFgivingherlocationandETA,whichherfriendinSantaCruzcancheckbecauseshelistedherasatripbuddy.Onthewayback,italertsZipcaroftheETAatitsparkingplace.

• Inhersparetime,sheembellishesherprofilebylinkingherRFaccounttoherFacebookaccount.Theonlyadditionalworkistospecifywhatprospectivetravelpartnerscansee.

o Justthefacts:thebeginning,end,andtimingofatrip,plusapricewhendriving.

o Careful:WhatanyFacebookmembercansee.o Friend:WhatFacebookfriendscansee.

• AFacebookfriendwhohappenstobeaprospectivetravelpartnercanseetheFriendinformationinanycase.Cherichooses"Careful".

• SheratesherexperiencewithZipcar“good”whenaskedbyRF• Aweeklater,whileoutclubbingshewantstogohomeearlierthanherfriendswho

broughther.ShecontactsRFthroughhercellphonetoseethepossibilities.• RFcheckstaxis,Muni,andciviliansandsuggests

o TerryTheatergoer,anacquaintancethat,unbeknownsttoCheri,isatanearbytheaterthatgetsoutsoon.She'lltakeherhomeforfree,butwillbeavailable20minutesfromnow.Tripwilltake23minutes.

o Ataxithatwillarrivein3minutesandcharge$13.Tripwillbe23minutes.o TheMuniisavailablefor$1andwilltake1.1hourincludingatransfer.

• CherichoosesTerry,followsherprogresstotheclub,andgoesoutsidepreciselyasshepullsup,waitsforher.Therewasnochargesincenomoneywasexchanged.CheriandTerrycouldhavegoneoutsideRFafterdiscoveringeachother,butpreferredusingitsrendezvoussupport.

3.1.2 Larry Language Learner Heregisterstobeeitheradriverorarider;andchecksthe“PracticeMandarin”boxinthespecialinterestssection.HefindsseveralnativeMandarinspeakerswhoridewithhimandpracticetheirEnglishhalfthetime.

3.1.3 Harry Hitchhiker Hitchhikingseemstohavedied,butHarryandmanyofhisfellowEastBayexecutivesarestillatit.HelivesinPiedmontandworksinSanFrancisco'sfinancialdistrictasastockbroker.Helikesreadingmorethandriving.Mostmorningsheusedtowalktoabusstopandsomeoneoftenpickedhimupanddrovehimtoastandarddrop‐offplaceinthefinancialdistrict.ThedrivergottheadvantageofusingtheHOVgatetogetacrossthebridge.IfHarrydidn'tgetarideafterawhile,therewasalwaysthebus.Thereisaculturaltraditionthattheriderdoesn'tspeakunlessinvited.ActivistDanKirschnerinstitutedasystemofdestinationspecificpick‐upspotsinSanFranciscothatallowpeopletoreversetheprocess

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althoughthedivershavelessincentivesincethereisnotollintheEastwarddirection.HarrytriedKirshner’sRideNow!systemuntilitwasdiscontinued.NowheusesRF,whichworksbetterbecauseofitsimprovedcellphoneinterfaceandsomewhatdifferentmodel.

• ShortlyinadvanceofhisdesireddeparturetimeHarrysendshisdesiredtriptoRF.• RFfindsallthedriverswhohaveregisteredinterceptingHarry'slocationandgoing

nearhisdestinationandproposesthemtoHarry.Heispresentedalistalongwiththeirratingsforreliabilityandcongenialitygatheredfrompreviouspassengers.

• Heselectsone,sometimessomeoneheknowsfromPiedmont.• AstheymovetowardsarendezvousRFusestheirGPS'stokeepthemapprisedof

whereandwhentheywillmeet.

• WhenHarryentersandexitsthecartheirphonesperformaBluetoothhandshakeandRFrecordsthetriptransferringsomeMoneyfromHarry'saccounttothedriver's.

• Theconfirmationofrendezvousiscrucialtomaintainareliabilityratingfordriversandriders.Theseratingsareusedbysubscriberstodecidewhomtocontractwith.Aratingofunder95%isaredflagformostpeople.

• Theydon'texchangemoney,sotheserviceisfree.• ParticipantscangiveMoneytoeachotherindependently,too.Sometimespeoplebuy

themfromothers.

• Harryandwhoeverdriveshimeachgettherighttorateeachotheronathree‐pointscale:Good,OK,orBad.TheseratingsareaccumulatedbyRFandrevealedeverytenridessothatfiguringoutwhosaidyouwere“Bad”isverydifficult.IfyouratesomeoneasBad,RFwillneverlinkyouwiththemagain.

3.1.4 Patricia Parent Sheismarried,worksathome,livesonRussianHillandhasayoungchildenrolledattheFrenchAmericanInternationalSchool(FAIS).Shehasacar,butwouldprefertocarpool.

• Theschool(whichpaysRFafixedsubscriptionfee)recommendsRF.Shegoesthere,registers,andputsinherdesires:Carpoolbothwaysfivedaysaweek,8:00and15:00,betweenherhomeandtheschool,nomoneyexchange.

• RFfindstwoexistinggroupsthatgofromherareatoafewschoolsinFAIS'sareaandtworegisteredindividualsinterestedinasimilardeal.ItsubmitstheinformationPatriciawaswillingtosharewiththe"captains"ofthetwogroupsandtheindividuals.

• Inafewdays,Patriciagetsthreeinvitationstomeetthegroupsandoneoftheindividuals.Aftermeetingandjudgingthealternativesshejoinsonegroupwithfiveotherpeopleandagreestostartanew,two‐persongroupwiththeindividual,Joan.TheycreateaRFgroup,makingJoanthecaptainandspecifyingsomerulesfromasuggestedlist.

• EachgroupusesRF'scarpoolcalendarsystemthatmaintainstheplanforeachday:whodrives,whorides,recommendedroutes,specialtimerequests,a

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bulletinboard,etc.Itsortsoutsmanycomplicationsautomatically,buteachgroup'scaptainmonitorsitfrequentlyforexceptions.

• EachdriverusestheirGPS‐equippedcellphonetokeepparentsandschoolsuptodateontheirlocationandETA.

• Afterayear,PatriciaandJoanfindathirdperson,andPatriciadropsoutofthegroup,whichhassixpeopleinitbecauseitnecessitatedtoomanystopsforher.

• Patriciaandherbankerhusbandgive$1,000ayeartotheRFFoundationtosupportfreecommunityservices.

3.1.5 Oprah Overachiever OprahandherhusbandliveinAthertonandsendtheirkidstotheInternationalSchoolofthePeninsula(ISTP)inPaloAlto.Everymorningat7AMaschoolbuspullsupinfrontofherdoortotakesthekidsandotherneighborhoodchildrentoISTP.However,fouroutfivedaysshemustleavesthehouseat3PMtopickthechildrenupatschoolat3:30PManddrivethemtothecommunitybaseballfield,tenniscourts,orKumonschoolandbackhomeat6:00PM.Shecomplainsthatshehasbecomeafull‐timechauffeur.Shedoesn’tdiscusstheenvironmentasshepullsuptoschoolinherSUV.Shethoughtaboutorganizingcarpoolswithfellowparentsattheschoolbutdoesn’tknowthemwellenoughandisconcernedaboutthesocialembarrassmentthatwillresultifshebeginsacarpoolandfindsituncongenial.Theschoolitselfresistsorganizingthingsforsimilarreasons.RFcomestotheirrescuebyofferingtorunanexclusiveservicefortheschool.Theparentsassociationapproves,andtheschoolprovidesthebasicinformationtoRF,whichpromisesconfidentiality.

RFallowseachfamilytolayouttheircalendar,includingallnon‐schooltrips.Itproposeslink‐upsthatwork,alwayssignifyingwhetherthepartnerisfromISTPornotandrevealingonlyinformationtheparticipantswish.Someparentseventuallyopttoorganizetheirowngroups;butOprahpreferstoleaveallthearrangingtoRFonaday‐to‐daybasis.ThisnotonlysavesorganizingbutalsosavesembarrassmentifOprahorherkidsdecidetogivesomeoneaBadrating;RFneverlinksthemagainwhileOprahcanplaydumbwhensheseesthelosersatafund‐raiser.RFsavesOprah600hoursayearor25fulldays.

3.1.6 Camilla Commuter Camillaisatwenty‐somethingengineeratSpikeSourceinRedwoodCitybutlivesinSanFranciscoforthesociallife.Sheownsacar,butwouldratherridewithsomeoneelsesoshecanreadorworkforthehour‐longrushhourcommute.HerhoursatSpikeSourceareregular,8:00to5:00,butoftengetextendedanhourortwo.EveryfewweeksshehasameetingorerrandsomewhereelseonthePeninsulainthemiddleoftheday.UnlikeOracleandothercompanies,SpikeSourceiscurrentlytoosmalltoprovidecommutersupportservices.

• SheregistersforRFandregistersarepeatingtripfromSFtoSpikeSource,fivedaysperweek.

• RFfindsthreeoptionsforher.1. CaltraintoRedwoodCity($4),ReservedTaxitoSpikeSource($15).Travel

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time:1.2hrs.2. CaltraintoRedwoodCity($4),bicycletoSpikeSource.Traveltime:1.6hrs.3. GaryBauerLuxuryVan,$20eachway,1.4hourscountingotherstopsinSF

andRedwoodShores.Oneweek'scommitmentisrequired.• Shetriesalloptions.

1. workswellbecauseshecanoftengetaridewithacolleaguetothetrainstationgoinghome.Also,thetaxicanbeshared,soCamillaorganizesataxi‐sharingpool,usingRF,amongseveralpeopleworkinginthesamevicinityandusingthesametrains.Thereservedtaxicanbecanceledwithoutpenaltyonehourbeforepick‐up.

2. Bicyclingisfineduringdaylightsavingswhenworkendsontime,butlesspleasantotherwise.

3. isnicetodosomeweeksbecausethevanshaveWiFi,coffee,snacks,TV,andacongenialgroup.Itmustbecanceledadayinadvance,however.

• HeroccasionaltripsaroundthePeninsuladuringthedayarehandledbytaxiorshejustdrivestoworkonsomedays.

3.1.7 Charlie Car Switcher CharlielivesinRussianHillandworksatPARCinPaloAlto.Hehastriedeveryoneheknowsinbothplacesandneverfoundacarpoolpartner.HeenrollsinRFdescribinghisdailycommuteneedsanditsuggeststwopossibilities.

• StartthecommutewithRhondaRussianwholeaveshisneighborhoodat8:00forherjobinRedwoodCity.ThenrendezvouswithPeterParkerwholivesinBurlingameanddrivestoPARC.RFnotesthatthereisafifteen‐minutewindowduringwhichbothdriversarecloseonHighway101.Normally,Charliewouldthinkthisveryundependable,butRF’scontinuoustrackrendezvousserviceallowsthedriverstoadjusttoanyhighwaycontingency.Normally,theydothechangeattheAnzaexchangeon101,butsometimesadjustiftrafficconditionsrequireit.

• StartthecommutewithBorisK.whodropshimoffatCaltraininSanFrancisco.TakeCaltraintothePaloAltostationwhereSallyS,whodrivestoPARCfromNewarkwillpickhimupfortherestofthetrip.Again,cellphonescoordinatedbyRFarecrucialforcopingwithanydelaysormix‐ups.

Charliechoosesthefirstalternativeandsimilaronefortheridehome,onthetheorythatasingletransferbetweenconveyancesislessriskythantwo.

3.1.8 Peter Parknride PeterlivesinSanFranciscoandusuallydriveshisjobinSanJose.Hewouldlikeawaytoreadratherthancopewithtraffic,butistoofarawayfromtheSanFranciscoCaltrainstation.HeenrollsinRFandamongthefewconventionalcarpoolingoffersgetsthesuggestionthathedrivehisowncartothePark‐and‐RidelotinBrisbaneandthenmeetothercommuterscomingdown101ortakeCaltraintoSanJose.Thetraintakesabout30minuteslongerthandriving.Thissolutionappealstohimbecauseithasmanybackupoptions.First,therearefarmoreopportunitiestogetaridefromsomeonedrivingdown101whenhearrivesatthePark‐

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and‐Ride.Second,iftherearenodrivers,hecantakeCaltrainandbeonly30minuteslateforwork.Third,hecangetbackontheroadwithhisowncar.Inthebeginning,hearrangesridesfromthePark‐and‐Rideonthenightbeforebut,whenthatfails,heusestheRFmobileaccesstoeitherfindalate‐registeringPark‐and‐Ridedriverorbecomeadriverforsomeoneelseinhissamesituation.Inotherwords,aPark‐and‐RidesitewithenoughRFsubscriberscanbecomeareal‐timemarketplaceatwhichmanydriversmeettosortoutwhodriveswhomeachday.Eventually,CaltransfacilitatesthisactivitybypostingsignsforvariousSouthBaydestinationswherepeoplecancongregate.However,theservicesofRFarestillusefultosupportreturntrips;evenifPeterfindssomeonetotakehimtoSanJose,hemightdrivehisowncarifheisunsureofaconvenientreturnplan.

3.1.9 Oscar Opera Lover HelivesandpracticesdentistryinPaloAlto,ownsacar,andoftenattendstheSanFranciscoOpera.Hecoulddrivetotheopera,butthetripisadragafteradayatwork.

• HeregisterswithRFandrequestsaroundtripridetotheOperaHouseafewdaysinadvance.

• RFgetsoffersfromtaxicompaniesinPaloAltoandSFtomeetscheduledCaltraintrains.ThetaxicompanieshaveregisteredstandardrateswithRF,sotheirresponseisautomatic.Caltrainneedn'tbecontacted,sincetheydon'tnegotiate.

• RFfindstwooptionsandpresentsthemtoOscar:1. SallyfromSunnyvalehappenstobegoingtotheoperathatnightandhas

registeredherexpectedscheduleandprice($15,becauseshecoulduseHOVlaneandisgoinganyway.Costofgasandparkingisabout$30).RFestimatesthetraveltime,includingthetimetopickupOscar.SallyagreedtoscheduleandpriceaftercheckingOscar'smemberinformation.

2. TaxiPaloAltoTrainStation/TraintoBART/BARTtoCivicCenter/WalktoOperaHouse,Cost:$14(includingRF's$1fee=min($1,10%oftransportcost)),TravelTime:1:30h.Return:TaxitoSFstation/TraintoPaloAlto/TaxihomeCost:$24,Traveltime2:50h,including1:15waitfortraininSF.

• OscarchecksSally'sreputationandchoosesher.Hedoesn'tlearnanythingelseaboutSally(evenhergender)becauseSallyhasspecifiedminimumexposureinherprofile.

• RFchargesOscar'saccount$16,thensendsconfirmationtoOscarandSallywithlocation,times,andaone‐timecredentialsthateachofthemloadsintotheircellphones.

• OntheappointeddaySallysetsoffforPaloAlto,placingherGPS‐equippedcellphoneonthedashboard,settocommunicatewithRF'strackerusingWiMax,WiFi,orCellNetwork(whateverisavailable).

• RFprovidesSallydrivingdirections,displayingamaponthephoneandgivingturningcommandsbyvoiceinherBluetoothearphone.

• OscaractivateshisphoneandseesasimilarmapshowingSally'slocationandETA.• AsSallyapproachesOscar'shousetheirphonesmakeappropriate,briefnoises.• Sallyarrives;theygettheircellphonestohandshake,confirmingtheiridentitiesand

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thecontract.Oscargetsinthebackseatanddoesn'ttalkuntilSallygiveshimpermission,aRFconvention.

• TheydrivetoSF,park,andwalktotheOperaHouse.TheircellphonessendthetimeofarrivaltoRF,allowingthemtoindicatesatisfactionsofaranddesignatearendezvousplaceforaftertheopera.

• Aftertheopera,theymeetwiththeaidoftheircellphonessignalingproximity,walktotheparkinggarage.SallyinvitesOscartositinthefrontseatforthereturntrip.

• Sally,againaidedbydirectionsfromhercellphone,drivesOscarhome.TheircellphonesconfirmthesatisfactoryendofthecontracttoRF,whichtransfers$15toSally'saccount.

• SallyandOscarexchangeemailaddressesandtentativelyagreetocarpoolagainforotheroperas.EachrepliestoRF’squerybygivingeachothergoodratings.

• Timepasses.• Foranotheropera,Oscarrepeatstherequestforatrip.RFfindsonlytheCaltrain

optionthistime,sohedecidestodrivehimselfafterlearningfromSallyviaemailthatshe'snotgoingthistime.

• Timepasses.• SallyemailsOscarthatshe'sgoingtoanoperaintwodays.Sinceheistoo,theyagree

tocarpoolagain,thistimewithnoformalcharge.TheygothroughtheRFprocessagainsoastogettherendezvousanddirectionssupport,butSallyproposesa$0feeupongettingOscar'srequest.

• Theyproceedasbefore,butOscarpays$15fortheparking.• Timepasses.• OscarandSally,afterseveralmoreoperas,getmarried,andstopusingRFforopera

trips.

3.1.10 Claude Commuter HelivesinSanFranciscoandcommutestoRedwoodCity,a40‐minutedriveat55mph.Helikesdrivinghimself,butwouldliketohaveriderstogivehimaccesstoHOVlanes,shareexpenses,andmaybeconversation.Heisnotconcernedaboutpersonalsafety,butisnofonderofirritatingpeoplethantherestofus.HewouldliketoreduceCO2emissionsifit’seasy.HeregistershisMonday‐FridaytripwithRF(25thAvenueto280to84toRedwoodCity,7:30‐8:45,andreturning17:30‐18:45)andhistolerancefordetourtime(20%)anddesirednumberofriders(3),typeofcar(BMW).

Heisgivenfourpossibleregularcommuterswiththeirstartandendpointsandtimes.Threeofthemareidentifiedjustbytheirtravelinformation;thefourthallowshisprofiletobeseen.Allhaveaveragetogoodreputations.Claudeacceptsthefourthandasksformoreinformationabouttwowhofithiscommutewell.

Oneofthetwoanswerbygivingsomepersonalinformationandheacceptsthem.RFprovidesasuggestedroutewithpick‐upanddrop‐offtimesforeveryone.Thethreepeopleareputinagroupsothattheycanusethecalendarsystemtopermittimely

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notificationsofcancellations.ClaudeasksRFtoputhimonthehitchhikers’menuforextrarides.AshestartshisrouteeachdayheactivateshiscellphoneandRFplotshisstoredroute,rememberinganycancellationsandsometimesfindingsomeoneadditionalforhimtopickup.ClaudeandhisgrouphavetheirestimatedCO2savingstalliedanddisplayedontheirindividualandgrouppages.

3.1.11 Tom Taxidriver TomisSanFranciscocabbie.HisregioncoversallofSanFrancisco,tripstotheairport,andstopsinbetween.HeleaseshistaxifromYellowCabandworksthemaximumtenhourspernight.Hemakesabout$300perdayafterpayingabout$90toYellowand$100forgas.Hepays$60/weekforthedispatchingservice.Hewouldliketomakemoremoney.HeusedtodependonYellow’sdispatchingserviceforfarespluspickingupridersatpopularplacesandtimes.AfterbuyingaGPScellphoneandsigningupforRFhismethodschanged.HespecifiedhisregionasSanFranciscoandSanMateocountiesandspecifiedhisshiftfrom16:00to02:00.Hestartedwiththe“Askme”dispatchingservicewhichproposedtripstohisphoneandacceptedone‐buttonresponses.HediscoveredduringbusytimesthatRFwasdoingbetterthanotherdispatchersorhisstreetpickups,sohewouldswitchtothe“I’myours”service,allowingRFtoscheduleandrouteallhisfares.RFislicensedastaxidispatcherandadvertisesitselfasRainbowTaxisinceitwillsupportanytaxifromanycompany.IttracksTom’scabcontinuouslyandoffershisservicetoallappropriateriders.Itdictateshisroutesbasedontrafficconditionsandlocatessecondandthirdridersforhisroutesifallridersareagreeabletothe“oneblockoutofyourway”sharingagreement.RFcollectsnegotiatedfaresfromeachriderandpaysTomweekly,charging$0.50perrider.ThestandardrendezvoussupportfeatureshelpTomandhisriderslocateeachotherwithlessanxiety.Hebuysaroofdisplaythatflashesarider’snametakenfromhiscellphone.

Tom’soccupancyratedoubles,andhistipsincreasebecauseridersarepayingRFforthefare.He’shappytobeaccumulatinglesscashlateatnight.Also,thefactthateveryRFcustomerisregisteredandtrackedduringaridemakeshimfeelalittlesafer.InidleperiodsRFsuggestsplacesTommightgotobemoreavailableforanticipatedriders.RF’sextensivehistoricaldatabasemakesitabetterpredictorofriderdemandthanTom’sintuitionorother,smallerdispatchers.Also,itusesinformationaboutallitsclientvehiclestospreadtheirsupplybasedonpredicteddemand.Intheend,hisnightlyincomerisesto$700,includingthesavedcostofhisoriginaldispatcher.

3.1.12 Cab Companies ThecompanieshearfromtheirdriversaboutRFandbegintonoticelesstrafficthroughtheirdispatchersthatareindependentservices.Eventually,mostdiscontinuetheirdispatchingservicesinceitwasafreeservicetothedrivers.TheyredirecttheirphonenumbertoRF,whichagreestogiveeachcompanypriorityforanyriderthatcallsthroughitsnumber.RF’spredominanceasaSanFranciscodispatchermakesallthetaxismoreactivebecauseofitsabilitytomarshalmoredemandandbalanceloadsindifferentregions.

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3.1.13 Victor’s Van Service Victorrunsahigh‐endlimoandvanservicewithtwentylimosandtenvans.Herentsthemforfourormorehoursatatimetogroupssizedfromfourtosixteen.Allhisdriversworkonawill‐callbasis.Theaveragevehicledutytimeis17hoursperweek.Hewouldliketoexpandbusinessbutcan’tcompetewithSuperShuttleandlargerlimoservicesthathavemoremarketingmuscle.

HeregisterswithRFlikeacabcompany,equipstwolimoswithGPScellphonesandWiFiandchoosesaregionsuggestedbyRF,RedwoodCitydowntoSanJose.Thelimosareadvisedtocirculateinthe101corridorwhenidle.SiliconValleyworkersthathavebeenusingRFforcommutingtrythelimousinesforlocalbusinesstripsbecauseoftheWiFiservice,theabilitytoscheduleatthelasthour,andthechancetohavepre‐meetingconferencesontheway.Theyareimmunetothefares,higherthantaxis,becausetheircompaniespay.Thelimosalsooperateastaxis,chargingtaxifaresandseekingmultiplepick‐upsanddrops‐offs.TheydoagoodbusinessservicingCaltrainstationsduringrushhours.

ToaccommodatelargergroupsVictorputsafewvansintoroamingservice.Herefitsthevanswithtables,projectors,andacomplimentarydrinkservice.LargerteamsstarttousethevansforbigmeetingsandeveninternaloffsitetripstoplaceslikeSantaCruz.Finally,VictorputsmorevansintoserviceforSanFrancisco–SiliconValleycommuters.ThevanscompetewellwithCaltrainandeventhefreecompany‐paidvansbecauseoftheirsuperioramenities.Eventually,somecompaniesreplacetheirdedicatedvanserviceswithVictor’s,usingRF’sdispatchingsystem.Somevansarededicatedtoasinglecompany’sstaff,buttheemployeesofanysignedupcompanycanrideanyopenvanwhenmoreconvenient.

3.2 New Technology Thissectioncontainsideasfortheunderlyingsystem.Figure6showsthesystemcontext.IntelligentcellphonesandinternetserviceslikeGoogleMapsindicatehowasystemcouldbebuiltthatmakesridesharingmuchmoredesirable.GPSandcelltowertriangulationmakeitpossibletotrackthelocationsofvehiclesandpeople.Powerfulcellphonesallowcontinualconnectionsbetweenpassengers,vehicles,andacentralscheduler.Computerschedulingandmachinelearningcanbeusedtogetthemostoutofapoolofvehicles.Thereisnolimittothestrategiesthatcanbeemployedtomaximizeconvenience.Realtimeschedulingcancoordinatethepoolwhiledemanddataiscollectedtoimprovetheplanningandcoordinationofvansovertime.Therearemanytechnicalchallenges:

• Systemschallenges,e.g.howtogetgood,real‐timelocationinformation• Databaseandalgorithms,e.g.real‐timescheduling,routeguessing,farenegotiation• Userinterface,e.g.specifyingroutes,notifyingdrivers.Creatingavoiceinterfacefordriversisessential.

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3.3 Use Cases

GeneralUser(eitherdriverorrider):1. Register2. Login3. AdjustProfile4. GiveFeedback

Driver:5. OfferRide6. Acceptrider7. CancelDrive8. TakeTrip

Rider:9. RequestRide10. Acceptdriver11. CancelRide12. JoinTrip

Operator:13. HandleEmergency14. AnalyzeandManagePerformance

Figure6.GrossSystemArchitecture

3.3.1 Register Actor:UserGoal:GetsetupinRFsoIcanarrangerideswithothers

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Scope:RFWebSite1. UsergoestoRideFriends.comreachingWelcomepage,possiblyviaFacebookorasimilar

relationshipsite.2. Userchooses“register”3. UserentersName4. Userentersemail(twice)5. Userchoosecreditcardpaymentmethod6. Userenterscellphonenumber,triggeringpotentialtextmessages.7. RFsendstextmessagetophonewithnumericcode8. Usechoosescommunicationspreferences(email,phone,orboth)9. Userenterscodeonwebpage10. UserentersBirthday,forcompatibilitymatching.11. Userenters%delayhewouldtoleratebeyonddrivingdirectly12. Userenterspricehewouldaskasadriver.$Fixed+$permile13. Userenterspricehewouldpayasarider$Fixed+$permile14. Userentersotherpreferences,tbd,e.g.“Doyouprefertodrive?”usedformatching15. Useclicks“Submit”16. RFacknowledges,recordsdata,andtakesusertohispersonalpage.

Extensions2a.Userchooses“login”,performUsecase23a.UserleavesNameblank,RFrequiresNamewhenSubmitisclicked.4a.Userleavesemailblank,RFrequiresemailwhenSubmitisclicked.4b.Userprovidesdifferingemailsblank,RFrequiresmatchwhenSubmitisclicked.5a.Userleavescreditcardblank,RFrequirescreditcardwhenSubmitisclicked.6a.Userleavescellphoneblank,RFrequirescellphonewhenSubmitisclicked.7a.Phonecompanyrejectsphonecall,RFasksfornewnumber.9a.Userleavescodeblankordifferentfromcorrectone.RFreportsandasksusertotry

again.10a.UserleavesBirthdayblank.RFentersdefault.11a.Userleavesdelayblank.RFentersdefault,e.g.30.12a.UserleavesBirthdayblank.RFentersdefault.13a.Userleavesdriverpriceblank.RFentersdefault.14a.Userleavesriderpriceblank.RFentersdefault.

3.3.2 Login (boring) 1. Riderlogsin,supplyingemailaddressandpassword.

3.3.3 Adjust Profile (a lot like Register) 3.3.4 Give Feedback Actor:UserGoal:UserreportsonsatisfactionwithrecenttripsothatRFchoosesdesirablepartnersforfuturetrips.Scope:UsercellphoneinteractionLevel:SeaLevelMainSuccessScenario:

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1. RFsendstextmessagetoUsersphonewithinanhourofacompletedtrip,askingforevaluation,e.g.Bad,OK,andGood.

2. Usercheckssimplereply,optionallyaddingtextandsendback.Extensions

1a.Iftripisfirsthalfofroundtrip,RFdoesnotsendmessage.1b.IfTelcorejectsphonecallRFsendsanemailtoUseraskingtofix.2a.IfUserignores,RFforgetsaboutit.

3.3.5 Offer a Ride PrimaryActor:DriverGoal:Driveroffersaridesothatshehavecompanionsandlowerdrivingcosts.Level:SeaLevelStakeholdersandInterests Driverwantslimiteddelay,decentmoney. RFwantsthecommissionPrecondition:DriverhasanaccountonRF,hasloggedintoRFSuccessGuarantee:Completeandcorrectrideinformationisstoredformatchingtopossibleriders.MinimumGuarantee:TheRFdatabaseisnotcorruptedbyincompleteorerroneousdata.MainSuccessScenario:

1. Drivergoesto“offeraride”page.Andfillsina. Dateb. Departuretimec. Returntripdeparturetime(optional)d. StartAddresse. EndAddressf. Repeatpattern(EveryWeekday,onceperweek)(optional)g. Maximumnumberofriders

2. Driversubmitsoffer.3. RFacknowledgesandstoresrequest.Ifrequestisforrepeatingride,storesin“Repeating

Schedule”.Extensions

1a.Ifdate,times,oreitheraddressaremissingRFcomplainsatsubmit.1b.Ifeitheraddresscannotbefoundinmapdatabase,RFasksforclarification,alaGoogle1.c.Returntimeisbeforedeparturetime 4.c.1.RFdisplayserrormessage

3.3.6 Accept a Rider PrimaryActor:DriverGoal:Driverwantstogiveridefortohavecompanionsandlowercosts.Level:SeaLevelStakeholdersandInterests: Driverwantslimiteddelay,decentmoney. RFwantsthecommissionPrecondition:DriverhasanaccountonRF,hasofferedaride.SuccessGuarantee:Driveragreestogiveride.ContractisstoredinRF’sschedule.MinimumGuarantee:TheRFdatabaseisnotcorruptedbyincompleteorerroneousdata.

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MainSuccessScenario:1. RFsendsdriveraproposalincluding

a. Dateb. Departuretimec. Pick‐upaddress(withoutstreetnumber)d. Estimatedarrivaltimee. Paymentofferedf. Pointertocompleteproposedcontractwhichadditionallycontains

i. Proposeddrivingrouteandscheduleii. Returnrouteandschedule(ifapplicable)

2. Driveracceptsoffer3. RFsendsdriver(andrider)confirmationandpointertocontractthatincludes

a. Dateb. Departuretimec. Nameandemailofdriverandriderd. Exactpick‐upaddresse. Estimatedarrivaltimef. Paymentg. Drivingrouteandscheduleh. Returnrouteandschedule(ifapplicable)

Extensions2a.Driverrejectsoffer.RFacknowledges(andinformsrider).3a.Ifmoreridersordriversareadded,RFupdatescontractandnotifiesdriver.

3.3.7 Cancel Drive PrimaryActor:DriverSecondaryActors:RidersandotherDriversPrecondition:Driverispartofanexistingcontract,hasloggedinGoal:WantstowithdrawfromcontractScope:CellphoneandwebinterfacesLevel:UserGoalStakeholdersandInterestsMainSuccessScenario

1. Driverlocatescontractandcancels.2. RFnotifiesallotherparticipantsandrestartssearchfordriverforopensegment.

3.3.8 Take a Trip PrimaryActor:DriverSecondaryActors:Riders,continuationdriversPrecondition:Driverandridershaveagreedtocontract.Driverhaslocation‐awarecellphoneturnedon.Goal:Traveltodestinationwithoutincidentandontime.Scope:CellphoneandwebinterfacesLevel:UserGoalStakeholdersandInterestsDriver:Wantstominimizedifficultyandgetpaid.Riders:Wanttoreachdestinationsafely

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MainSuccessScenario:1. RFremindstostart5minutesbeforescheduledstart,notified(viaemail,IM,SMS,or

whateversheprefers)andreferredtocontractdocumentcontainingpeople,schedule,map,etc..Drivercanprintifhe’sonacomputer.

2. Driver’scellphonesendsRFlocationinformationeveryfewminutes.3. RFnotifiesrider5minutesand0minutesbeforethearrivalofdriver.Riderscanalso

accesscontractdocumentanytimetoreviewplan.4. Whenaridergetsinthecar,hercellphonehandshakeswithdriver’sandreports

rendezvoustoRF.5. Uponarrivalatdestination,allcellphones“de‐handshake”andreporttoRF.6. RFrequestsfeedback.Seecase4.7. Accountofdriverandriderareupdatedwithagreedpayment.

Extensions1a.Multipledriversareneeded.RFremindsdriverswellbeforethetransfertimeandreports

thepositionandprogressoftheprevious.HiscellphonereportshispositiontoRF.3a.Moreridersarewaiting.Repeatsteps3and4foreach.5a.If“destination”istransfertoanotherdriver,RFnotifiesnewdriverthatriderhasreached

rendezvouspoint.5b.Ifrendezvousisjeopardizedbydelays,RFinitiatesemergencyprocedures.Seecase11.

3.3.9 Request a Ride PrimaryActor:RiderGoal:requestaridesothatshecanavoiddrivingandbesafeLevel:SeaLevelStakeholdersandInterests Riderwantslimiteddelay,reasonablecost RFwantsthecommissionPrecondition:RiderhasanaccountonRF,hasloggedintoRFSuccessGuarantee:Completeandcorrectriderequestisstoredformatchingtopossibledrivers.MinimumGuarantee:TheRFdatabaseisnotcorruptedbyincompleteorerroneousdata.MainSuccessScenario:

1. Ridergoesto“Requestaride”page.Andfillsina. Dateb. Departuretimec. Returntripdeparturetime(optional)d. StartAddresse. EndAddressf. Repeatpattern(EveryWeekday,onceperweek)(optional)

2. Ridersubmitsoffer.3. RFacknowledgesandstoresrequest.Ifrequestisforrepeatingride,storesin“Repeating

Schedule”.Extensions

1a.Ifdate,times,oreitheraddressaremissingRFcomplainsatsubmit.1b.Ifeitheraddresscannotbefoundinmapdatabase,RFasksforclarification. 3.a.RFdisplayserrormessageonloginscreen1.c.Returntimeisbeforedeparturetime 4.c.1.RFdisplayserrormessage

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3.3.10 Accept a Driver PrimaryActor:DriverGoal:Driverwantstogiveridefortohavecompanionsandlowercosts.Level:SeaLevelStakeholdersandInterests: Driverwantslimiteddelay,decentmoney. RFwantsthecommissionPrecondition:DriverhasanaccountonRF,hasofferedaride.SuccessGuarantee:Driveragreestogiveride.ContractisstoredinRF’sschedule.MinimumGuarantee:TheRFdatabaseisnotcorruptedbyincompleteorerroneousdata.MainSuccessScenario:

1. RFsendsrideraproposalincludinga. Dateb. Departuretimec. Estimatedarrivaltimed. Paymentaskede. Pointertocompleteproposedcontractwhichadditionallycontains

i. Proposeddrivingrouteandscheduleii. Returnrouteandschedule(ifapplicable)

2. Rideracceptsoffer.3. RFacknowledgesandasksridertowaitforconfirmation.4. RFsendsconfirmationandpointertocontractthatincludes

a. Dateb. Departuretimec. Nameandemailofdriverandriderd. Exactpick‐upaddresse. Estimatedarrivaltimef. Paymentg. Drivingrouteandscheduleh. Returnrouteandschedule(ifapplicable)

Extensions2a.Ifriderrejectsoffer,RFacknowledgesandsaysitwillkeeplooking.4a.Ifmultipledriversareinvolvedrendezvouspointsandsecondarydriversareincluded.4b.Ifmoreridersareadded,scheduleisupdatedandriderisnotified.

3.3.11 Cancel Ride PrimaryActor:RiderSecondaryActors:Driver(s)andotherRidersPrecondition:Riderispartofanexistingcontract,hasloggedinGoal:WantstowithdrawfromcontractScope:CellphoneandwebinterfacesLevel:UserGoalMainSuccessScenario

1. Riderlocatescontractandcancels.2. RFnotifiesdriver(s).

Extensions2a.Ifthereareotherriders,RFreworkscontracttoremoveriderandnotifiesother

participantsthatachangehasoccurred.

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3.3.12 Join a Trip (See case 7)

3.3.13 Use Case 13: Handle Emergency (TBD)

3.3.14 Use Case 14: Analyze and Manage Performance (TBD)

3.4 Nonfunctional Requirements

RFwillbeimplemented“inthecloud”withanetworkofcomputerssothatitcanmecontinuouslyscaledupforloadandredundancy.Userswillaccessitfromwebbrowsersrunningondesktoporlaptopcomputersandphones,usingvoice,SMS,andwebaccess.RFwillinterfacewithatrafficmonitoringsystem,e.g.theCaltranssystem.RFisanSaaSandshouldmatchothersuchservices,e.g.Google,inallfeatures,unlessotherwisespecified.The“ilities”arelistedinpriorityorder.Theannotations(Importance,Difficulty)areaddedtocertainitemsratingthemHigh,Medium,orLow.Whennothingissaid,assume“doitlikeGoogle”.3.4.1 Usability 3.4.1.1 Computers UseCases:1,6,10Ambition:Registration,requests,offers,responses,andreviewsaresimpleandfrictionless(H,L)

Scale: Minutesforanyatomicoperation.Meter: Stopwatchmeasurementof20newusersperformingeachtypeoftaskthreetimes.Must: Lessthan10%ofusersfailtocompleteanoperation.Nooperationtakesmorethan

fiveminutes.(H,L)

Wish: Lessthan2%ofusersfailtocompleteanoperation.Nooperationtakesmorethanoneminute.(M,M)

Platform: Anywebbrowserwith5%ofmarket.(M,H)3.4.1.2 Phones UseCases:7,8,9,11,12

Ambition: After15minutesoftrainingausercanunderstandavoicemessageandrespondusingvoiceveryquickly.Anofferorrequestcanbeofferedbytextorvoicequicklyandsimply.(H,H)

Scale: Secondsofelapsedtimeafterinitiationofmessage.Meter: Stopwatchmeasurementof20elderlyusersdrivingacarathighwayspeeds.

Must: OffersandRequestsenteredwithtextusingsimpleinterface.Acceptingorconfirmingoffersdonebyvoiceorshortkeypresses.Usercanunderstandvoicequeriesafteratmostthreerepeats.Usercanrespondwith“yes”or“no”within60secondsofmessagebeginning.(H,H)Dialogisduplicatedintextoncellphone.

Wish: Offersandrequestscanbemadebyvoicewithfeedbacktoconfirm.Userunderstands

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firstmessage,canrespondin15seconds.Platform:Anycellphonewith5%marketshareinanycountry.(M,H)

3.4.2 Availability

3.4.3 Integrity

3.4.4 Efficiency UseCases: 6,7,8,9,10,11Ambition: Serviceapproachesthespeedofhitchhikingbythesideoftheroad.Anagreement

requiresarequest,adriveroffer,arideracceptance,andaconfirmation;soanagreementtakesatleastthreetimesthemessagetransmissiontime.

Scale: SecondsofelapsedtimefromclickMeter: Stopwatchmeasurementof100simplemessagessentandreceivedfromcomputers

andphoneswhileRFisreceiving1000messagesperminute.Must: Starttimeminutesaway:3minutes(M,H)

Starttimehoursaway:15minutesStarttimedaysaway:60minutes

Wish: Starttimeminutesaway:30seconds(M,H)Starttimehoursaway:5minutesStarttimedaysaway:30minutes

Platform: NetworkofstandardIntelprocessors3.4.5 Reliability

3.4.6 Interoperability 3.4.6.1 User Computers UseCases:1,6,10RFshouldworkonanywebbrowserthathas5%ofthemarketinanycountry(M,M)3.4.6.2 User Phones UseCases:7,8,9,11,12RFshouldworkonanycellphonethathas5%ofthemarketinanycountry(M,H)3.4.6.3 Traffic Monitors UseCases:9RFmustbeabletoreceivetrafficspeedindicationfromlocalservice,tbd.

3.4.7 Testability UseCase:15Ambition: ThisisaninnovativeSaaSsystem,anduserpreferencesandcapabilitiesarenotwell

known.Theearlyversionsshouldproduceextensivedataonrobustness,usability,andnewrequirements.Asmuchas25%oftheearlycodeshouldbedevotedto

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reportingonusepatterns.Scale: Everyuserinteractionshouldcontributetoaggregatedata.Meter: Observationofdailyoperationandreports.

Must: Serioususerdifficultiesshouldbedetectedandreportedinadailyreport.(H,L)Timeprofilesofusearereported,e.g.howfarinadvancedousersofferorrequestrides.(H,L)Satisfactionreportsareproducedweekly.(H,L)

Wish: Newrequirementsaredetectedbyfollowinguserbehavior.(M,M)Platform:NetworkofstandardIntelprocessors

3.4.8 Robustness

3.4.9 Flexibility

3.4.10 Maintainability

3.4.11 Portability

3.4.12 Reusability 3.4.13 Expected Architectural Tradeoffs Phonecoveragevs.UsabilityEfficiencyvs.Usability3.4.14 Human Backup, Legal, Political, Organizational Issues AsmallstaffofhumanoperatorswillbeavailabletohandleemergenciesthatRFcannot.Theoperatorwilltypicallytalktodriversandridersviaphone.ThemustbetrainedonhowtoscheduletripsinRFbyfiatandhowtohandleverydistraughttravelers.ThesystemmustbedesignedlikecurrentautomotiveGPSsystemssothatitdoesn’tdistractdrivers.Certainregulations,e.g.restrictionontaxispickingupmultiplefares,mustbeunderstood,compliedwith,oraltered.Ifsuccessful,RFwillreducecongestion,pollution,andloneliness.OperatorsetspaymentsfromriderstodriversandcommissionstoRFglobally.Theprocessofmatchingshouldtakeintoaccountpersonalpreferenceswhenmatchingpartnerswhosetripsarecompatible.

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Alloperationsmustbepossiblefromeithercellphoneorwebbrowser.Ahumannedservicedeskisneeded.Theinformationdisclosedaboutanysubscribershouldbeminimizedsubjecttothegoalofachievingmatches.Subscribersreportingnegativeexperiencesshouldbeprotectedfromdetection.Inotherwords,thesystemshoulderroronthesideofcomplainers.Roundtripsandrepeatingtripsarebrokendownintoasequenceofindividualtripsandaresubmittedtothematchingprocessattheappropriatetime,e.g.nosoonerthansevendaysbeforethetrip.3.4.14.1 Dependencies RFneedstolinkwithsocialnetworkingsitesItneedsmasstransitinformationItneedsasourceofadvertisinglikeAdSense

3.5 Product Roadmap

Investigationshaverevealed• Humanpreferencesandhabitsarethebiggestobstacletosuccess.

o DrivingaloneistheAmericanwayoflife.IntheBayArea76%ofcommutersdrivealone.

o Manyridesharingserviceshavefailedforlackofacriticalmassofusers.o Christensenwarnsagainstbasingabusinessonchangingbehavior.

• Themostaccessiblemarketisspecificlargecompanycampuseswithathousandormoreemployees.

o Thesinglelocationandcommontimeschedulesconcentrateneeds.o Co‐workersaremoretrustingofeachother.o Sellingcanbeconcentratedonasmallnumberofpeople.o Somecompanieswillwelcomehavinggreennesstakencareof.

Themajorimpediment—andbiggest“knownunknown”—appearstobehumanbehavior,learningmoreaboutitisthetoppriority.Theengineeringchallengesseemlessdaunting,andthetechnicaldesignoftheproductshouldbedrivenbydiscoveredcustomerpreferences.Thus,weareadoptingalearn‐build‐sellsequenceofproducts.3.5.1 Learning 3.5.1.1 Goal Wewishforthreecompanieswithsuccessfulridesharingprograms.Atleast,werequire,significantinsightaboutmarketandrequirements.Wemightdiscover“unknownunknowns”thatwillrequirenewstudies.3.5.1.2 Time Duration Oneyearfromstartofproject.Plantosignupthreecompaniesinthefirstthreequarters.3.5.1.3 Product Features Theofferingisahigh‐touchservice,soldtocompaniesoneatatime.Thecomputersystemistheminimumwecangetawaywith:non‐stoptripmatching,web/emailinterfaceonly,noreal‐timesupportotherthanbyvoicephone.

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3.5.1.4 Engineering Produceasimplewhiteboxwebinterfacetoallowregistration,proposing,commit,andfeedback.Thereshouldbeextensivecustomertrackingperformedasspecifiedbymarketing.Thepurposeofthisreleaseisasmuchtolearnaboutcustomersasitistoprovidethemservice.Gettingthesystemupquickly(onequarter)iscrucialsothatwehavesomethingtosell.Weshouldconsideracquiringorevenpartneringwithanexistingservice.Thesystemwillrequirecontinualmaintenanceandenhancementthroughthefirstyear.WorkonRelease2shouldstart.3.5.1.5 Sales Weshouldsellone‐yearcontractstocompaniesforfree!Allweaskiscommitmentfromthetopandcooperationfrompersonneldepartmentstoapproachemployees.Smallcommissionsfromridesharerswillgeneratesomerevenue.3.5.1.6 Operations Eachcompanywillhaveanonsitecoordinatorwhopromotesthesystem,aidscommunication,solvesproblems.Thispersoncanbethesalespersonwhosoldthedeal.Theirrealassignmentistodeeplyunderstandandreportontheattitudes,preferences,andpracticesofthesubscribers.3.5.1.7 Marketing Asidefromguidingsales,themarketingeffortshoulddesignthequestionswewantansweredandstudyotherpotentialsubscribersoutsidethetargetcompanies.Someofthequestionsare

• Whatiscriticalmassofsubscribers.Howdoesitgrow?• Howdosubscribersbehave?• Whatmotivatessubscribersmore—relationshipsorcostsavings?• Whatarethepainpointsforsubscribers?• Whatdoesthecompanywantbesidesridesharing?• DoesintegrationwithaGPSnavigatorhelp?

3.5.2 Conquer the SF Bay Area 3.5.2.1 Time Duration TwoYears3.5.2.2 Product Features Addcellphonesupport,cross‐companypartnerships,andotherfeaturesfromtherevisedvisiondocumentthatemergesfromthemarketingstudiesofRelease1.Thissystemshouldexceedthecapabilityofanyotherknownsystem,e.g.makethelead‐timeforarrangingpartnershipsassmallaspossible,buildreliabilityandsafetyintotheprocess.3.5.2.3 Engineering Addcellphonesupport,real‐timetravelermonitoring,trafficmeasurement,sophisticatedfeasibilitymatching,andfeaturesdeemedessentialfromthemarketingstudies.Makewebsiteopentoallowregistrationbyanyoneinregion.3.5.2.4 Sales Offerinitialcompaniesacontinuationandsignupatleast10newcompanies.InitiatepublicsalescampaigninBayAreatoinvitecustomersfromanywhere.3.5.2.5 Operations Initiatecentralhelpdesk.Drawdownonsitesupportbyassigningsitemanagerstofourcompanieseach.3.5.2.6 Marketing Guidepubliccampaign.

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3.5.3 Conquer the United States 3.5.3.1 Time Duration Twoyears.3.5.3.2 Product Features UnchangedexpectforalterationofanySFBayAreaidiosyncrasies.SpanishLanguageversion?3.5.3.3 Engineering Maintenanceexceptforabove.BeginworkforRelease4.3.5.3.4 Sales Launchinanewregionforsixstraightquarters.Eachoneshouldproducetenin‐companydealsplusopencampaign.3.5.3.5 Operations DesignandimplementregionalofficesbasedonSFBayAreaexperience.3.5.3.6 Marketing Determinethesixregionstolaunchservicein.Considerfranchisingmodel.3.5.4 Conquer the World 3.5.4.1 Time Duration Threeyears.3.5.4.2 Product Features MultipleLanguages3.5.4.3 Engineering MultipleLanguagePlatform.3.5.4.4 Sales LaunchinthreenewregionoutsideUS.Forthreeyears.Eachoneshouldproducetenin‐companydealsplusopencampaign.3.5.4.5 Operations DesignandimplementregionalofficesbasedonUSexperience.3.5.4.6 Marketing Determinethethreeregionstolaunchservicein.Considerfranchisingmodel.

3.6 The Matching Process

Thissectionisanelaborationoftheearliersection2.2.2.2Thedatastructureisadirectedgraphwhereeachvertexrepresentsanintersectionofstreets,freeways,andraillines.Edgesrepresentplannedtravelbyadriver,bus,train,orothervehicle.Eachedgeislabeledwith

• itsarrivaldateandtimeatitsstartingvertex,• distancetotheendingvertex,• thedriver,and• thepredictedspeedofthedriveronthisedge.

Everypairofvertexeswithapassagebetweenthemalwayshasthreeedgesrepresentingthechoicesofdrivingalone,walking,andataxiride,withanarrivaltimesignifyingthattravelcanbeginimmediately.(Thisassumptionfortaxismustbeadjustedforarrivaltimeslessthan30minutesinthefuture.)

Fromtheedgeeandtherider’svalueoftimeonecancomputethecosttotheriderfor

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traversingtheedgeasCost(e,rider,waitTime)=e.distance*e.driver.price+(waitTime+e.distance/e.speed)*rider.valueOfTime

Findingarideforsomeoneamountstoasolvingacheapestpathproblem.Thecheapestpathisnotusuallytheshortestwhichislikelytobeadirecttaxirideoraverylongwalk.Whenadriverproposes,insertherchosenroutebyaddingtotheedgelistateveryvertexalongtheroute.Whenariderproposes,findthematchbyperformingacheapestpathsearchinthegraph.Whenadriver’stripendsremovealltheedgesassociatedwiththetrip.

3.6.1 Karp’s Algorithm WeadaptDijkstra’sclassicshortestpathalgorithm32usingideassuggestedbyBovetandKarp.7Itgeneratesdiversepathsfromasourcestoasinkt,allatmostctimesthelengthofashortestpathfromstot.

1. DefineD(x,y)astheEuclideandistancebetweenxandyandL(x,y)astheshortest‐pathdistancebetweenxandy.SoD(x,y)isalowerboundonL(x,y)andD(x,y)canbecomputedinconstanttimefromtheEuclideancoordinatesofxandy.

2. ConductsynchronizedDijkstrasearchesforwardfromsandbackwardfromtuntilL(s,t)isdetermined.By“synchronized”wemeanthatthenextvertexscannedisonewithaminimumpermanentlabel,amongallvertexesnotyetscanned,eitherintheforwardsearchorthebackwardsearch.WeexploitthefactthattheDijkstraalgorithmassignspermanentlabelstonodesinincreasingorderoftheirdistancefromthestartingpointofthesearch(i.e.,sort).Atanystageinthecomputation,definelowerboundsHs(v)andHt(v)asfollows:

Hs(v)=L(s,v)ifvhasalreadyreceivedapermanentlabelintheforwardsearch,andotherwise=max(D(s,v),thelargestpermanentlabelobtainedsofarforanyvertexintheforwardsearch).Ht(v)=L(v,t)ifvhasalreadyreceivedapermanentlabelinthebackwardsearch,andotherwise=max(D(t,v),thelargestpermanentlabelobtainedsofarforanyvertexinthebackwardsearch).

Weendthisstagewhenavertexxoccurswhichhasreceivedpermanentlabelsinbothsearches(i.e.L(s,x)andL(x,t)arebothknown,andL(s,x)+L(x,t)=minvHs(v)+Ht(v)).WenowknowthatL(s,t)=L(s,x)+L(x,t).

3. Letb=cL(s,t),wherecistheallowedapproximationratio.Wenowabandontheforwardsearch,sotheboundsHs(v)willnolongerchange.Continuethebackwardsearch,butnowscanningvertexesinincreasingorderofL(v,t)+Hs(v),aslongaswecontinuefindingnewvertexesvsuchL(v,t)+Hs(v)≤b.Afterthis,weknowL(v,t)foreachvertexvsuchthatL(v,t)+L(s,v)≤b.Allothervertexescanbediscarded.

4. Callapathfromstovagoodprefixifitscostislessthanorequaltob‐L(v,t).Restrictingattentiontovertexesthathavenotbeendiscarded,buildthetreeofgoodprefixes.Thereisanaturaltreestructureinwhichthenodescorrespondtogoodprefixesandthereisanedgefromeachgoodprefixtoeverygoodprefixthatextendsitbyoneedge.Theleavesofthistreeareinone‐to‐onecorrespondencewithpathsof

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length≤bfromstot.Theideaofthealgorithmistosimplykeepshootingdownthistreetodifferentleaves.Toavoidrepetitions,defineanodeofthetree(i.e.,agoodprefix)asblockedifachosenpathhasreachedeveryleafinthesubtreebeyondit.Aleafbecomesblockedwhenitisbecomestheterminusofapathand,recursively,aninternalnodebecomesblockedwhenallitschildrenhavebecomeblocked.Soateverystepthealgorithmshootsdownthetree,butavoidingblockednodes.Toachievediversity,wecankeepacountateachnodeofthenumberofpathsgeneratedsofarthatpassthroughthenode,and,whenmovingfromanode,alwayspicktheedgewiththesmallestcount,amongedgestonodesthatarenotblocked.Wedon'tbuildthetreeallatonce,butdosolazily,apathatatime.

Thespacerequirementisboundedabovebythenumberofpathsthathavebeengenerated,timesthemaximumlengthofagoodpath.Adefectofthismethodisthatitgeneratesnon‐simplepaths(i.e.,withrepeatedvertexes).Ifyouwanttorestricttosimplepathsdon'tallowagoodprefixtobeextendedtoavertexalreadycontainedinthegoodprefix.Thiswilleliminatecyclescompletelybutwillcreatedeadends.

Anydiscoveredpathmayinvolveswitchesamongdrivers,butthealgorithmshouldprefercontinuingwiththesamedriverbecauseswitchingvehicleswillinvolveawaitthataddstotherider’scost.

Adjustmentswillberequiredinpractice.• Ridersanddriversmaybewillingtoaltertheirplanstopartner.Forexample,aridethat

usesashorttaxiridemaybetweakedbyhavingadrivermakeadetourtoeliminatethetaxiride.Adrivermayalsobewillingtodelayhistrip.Wemighthandlethisbyalteringtheoriginaldriverrouteandproposingittothedriver.

• Eachdriverhasamaximumnumberofriderssoshouldberemovedfromthedatastructurewhenherconveyanceisfull.

Thecomputationcanrunonmanyprocessors,andsynchronizationisneededtopreservethegraph’sintegrity.Raceconditionsresultingfrommultipleoutstandingproposals,however,occuronlywhenadecidermistakenlyacceptstwoconflictingproposals.Toapproachtheconvenienceofsolodriving,thelead‐timeforarrangementsshouldbeshrunktominutesratherthandaysorhours.Asidefromsavingriders’planning,areal‐timesystemmightcopewiththemanycontingenciesoftravel.Hereisasketchofhowreal‐timeadjustmentscanbemade:

Uponreceivinganactivedriver’snewlocation:1. Locateherpositiononanedge.2. Tracethecontinuationofherrouteforward,updatingarrivaltimes.3. Fromthedriver’scontracts,findridersthatmaybeaffectedandre‐runthematching

algorithm,possiblytofindbettermatches.Re‐entercontractnegotiationsifappropriate.

Uponreceivingnewspeedinformationforanedge:1. Tracethecontinuationsofalldriverspassingthroughthatedgeintheimmediate

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future,updatingtheirarrivaltimes.2. Performstep3from“driver’snewlocation”procedure.3. Suggestbetterroutefordriver.Ifsheacceptschange,modifyoutstandingcontracts

appropriately.Untilariderhasmadeacontract,sheiskeptinthe“RideSeekersPen”whichisrerunthroughthematchingprocessperiodically.Asarider’sdeparturetimegetsclosershegetshigherpriorityinthepen.Also,whenadriverisaddedtoanedgeleavingherstartnodeorarrivingatherendnodeatabouttherighttime,anewmatchattemptshouldbetriggered.Theadditionofanewdriveronanedgethatlinksotherdriversintoafeasiblepathfortheriderseemsratherhardtodetecteasily.

ThedevicesdriverscarrymustcommunicatewithvoicethewaygoodGPSdevicesdotoday.Thereisnothingmoredangerousthanlookingatamaponacellphonewhiledriving.DesigningagooduserinterfaceforthesystemwilldrawuponandextendresearchinHuman‐ComputerInteraction.Ifthesystemacquiresalargeamountofhistoricaldataaboutridedemandandacomprehensiveviewofvehiclelocationsitcanprovidesuggestionsofwherefaresmaybeavailable.Itcanevenbalanceloadsbywarningdriversofanoversupplyofvehiclesatcertainlocations.Ofcourse,thisservicedependsupontheservicehavingahugesubscribership.

4 Glossary

Civilian:AuserotherthanaserviceCompatibility:AmeasureoftwofeasiblepotentialpartnersprobabilityofcontractingContract:AnagreementamongdriversandridersforaspecifictripCost:Ameasureofthetangiblecostofaparticularpartnershiptoeachparticipant.Decider:AproposerwhohasreceivedanofferDriver:ApersonoraservicewithavehiclewillingtoofferridesEnthusiasm:Asubscriber’spredilectiontopropose,representedbyadailyprobabilityFeasibility:AmeasureofthelogisticalmatchoftwoproposersMOD:MovingObjectDatabasePartner:AdeciderwhoagreedtoacontractProposer:AsubscriberwhohasproposedarideaseitherdriverorriderRelationship:AmeasureofthehumanrelationshipbetweentwodecidersRF:theRideFriendssystemRider:SomeoneseekingarideSubscriber:SomeonewhohasregisteredwithRFTrip:Acompleterouteforaparticulardriver.User:DriverorRider

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