road safety audit swanzey, new hampshire nh …...nhdot: 1. evaluate feasibility of reconfiguring...

Road Safety Audit

Swanzey, New Hampshire

NH 32/Sawyers Crossing Rd Intersection

February 12, 2013

Road Safety Audit Report

Table of Contents

I. Executive Summary ......................................................................................................................... 2

II. Road Safety Audit Process: .............................................................................................................. 3

III. Background Information: ................................................................................................................. 4

IV. NH 32/Sawyers Crossing Road Intersection ...................................................................................... 5

V. Traffic Data ...................................................................................................................................... 6

VI. Crash Data ....................................................................................................................................... 8

VII. Stakeholder Identified Risk Factors: ............................................................................................... 10

VIII. Risk Analysis and Mitigation Strategies: ......................................................................................... 15

IX. Benefit/Cost Analysis of Improvements: ........................................................................................ 16

X. Audit Response: ............................................................................................................................. 21

Table of Figures

Figure 1 – RSA Process ............................................................................................................................. 3

Figure 2 - Overview of study location ....................................................................................................... 4

Figure 3 - Project Location Map ............................................................................................................... 6

Figure 4 - AM Peak Hour Counts .............................................................................................................. 7

Figure 5 - PM Peak Hour Counts .............................................................................................................. 7

Figure 6 - Crash Data ............................................................................................................................... 9

Figure 7 - Southern leg of intersection ................................................................................................... 11

Figure 8 – NH 32 northbound at southern part of intersection ............................................................... 11

Figure 9 – Signage on splitter island ....................................................................................................... 12

Figure 10 – NH 32 southbound at second High School access point ....................................................... 13

Figure 11 – Sawyers Crossing Road turning left to drop children off at elementary school ..................... 14

Figure 12 – Speed limit reduces from 30mph to 20mph on all approaches............................................. 14

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Project Title: Swanzey, NH – NH 32/Sawyers Crossing Road IntersectionsDate Audit Conducted: February 12, 2013RSA Team and Participants:Town of Swanzey Sara Carbonneau Town Planner

Thomas De Angelis Police ChiefFrancis Faulkner Maintenance SupervisorShane O’Keefe Town AdministratorNorman Skantze Fire Chief

Monadnock Regional School Jan Parsons Assistant to PrincipalDistrict (MRSD)

Southwest Regional Planning J.B. Mack Sr. Transportation PlannerCommission (SWRPC)

NHDOT Michelle Marshall Safety EngineerMike Dugas Chief of Preliminary DesignWilliam Lambert Administrator, Bureau of TrafficDoug Graham District 4 EngineerJohn Kallfelz District 4 Assistant Engineer

FHWA Martin Calawa Safety & Operations Engineer

CHA Nicolas Bosonetto Project Engineer

Project Characteristics:

Audit type: Existing RoadsUnits of Measure: USAdjacent Land Use: Residential/InstitutionalPosted Speed Limits: NH 32 - 30 mph, Sawyers Crossing Road – 30 mph (20 mph school zone).Functional Classification: NH 32 – Major Collector, Sawyers Crossing Rd – Local RoadTerrain: LevelClimatic Conditions: Cold winters with snow – icing possibleLocation: Town of Swanzey, NH

NHDOT Project Number: 16215-F

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I. Executive Summary

Based on the Road Safety Audit conducted on February 12, 2013 at the intersection of NH 32 andSawyers Crossing Road in the Town of Swanzey, the following safety mitigation strategies arerecommended.

Short Term Solutions

NHDOT: 1. Study the placement, condition and adequacy of existing signage at this intersection andmake recommendations for improvements. Determine whether chevrons are anadequate option for the demarcation of NH 32 as it curves through the intersection. Aspart of this study, determine whether relocating the stop ahead and deer crossing signsis feasible, and whether yield signs are needed on the northwestern part of theintersection.

2. Repaint the school crosswalks after consultation with the Monadnock Regional SchoolDistrict (MRSD).

3. Determine appropriate actions needed to fix the pothole at the southern leg of theintersection.

Town ofSwanzey:

4. Continue to enforce speed limits at the intersection.5. Determine feasibility of removing large pine tree from intersection.6. Determine whether Simeneau Drive could become a one-way street.

MRSD: 7. Maintain sight lines at intersection by pruning trees on school property as necessary

Medium Term Solutions

SWRPC: 1. Conduct an Access Management Study in coordination with MRSD, Town of Swanzey,and NHDOT to determine appropriate strategies for consolidating access points to theTown Hall, Town Library, SAU offices, MRHS, Simeneau Drive and Mt. Caesar schools.This study should make specific recommendations as to the locations of curb cuts, theirwidths, and also how internal circulation patterns for the many parking lots can betterbe coordinated.

2. Work with MRSD and the Town of Swanzey to apply for a Safe Routes to School grant todetermine/fund improvements for pedestrians and bicyclists in this area.

Long Term Solutions

NHDOT: 1. Evaluate feasibility of reconfiguring intersection into a roundabout, T-intersection, orrealigning the southern leg of the intersection. Based on the analysis in this RSA, amodern roundabout is the better option with a Benefit/Cost ratio between 2.08 and1.72. A roundabout has the potential to mitigate 71% of all the crashes at theintersection, decrease traffic speeds in the area in front of the school from 40 mph to 20mph, and have the capacity to handle projected traffic increase for the next 35 years.The roundabout option can also enhance the rural character and natural beauty ofsurrounding small town atmosphere by incorporating landscaping and other contextsensitive details into the design.

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II. Road Safety Audit Process:

The intersection of NH 32 and Sawyers Crossing Road has been a safety concern for the Town ofSwanzey for many years. In 2012, the Town approached the SWRPC Transportation Advisory Committee(TAC) for inclusion of the intersection into the 10 year plan. The SWRPC suggested conducting a RoadSafety Audit (RSA) to determine appropriate mitigation efforts. Together with NHDOT, the SWRPCidentified the key stakeholders, owners, and consultants necessary to conduct the RSA and invited themto participate in the RSA process. This RSA Team was involved in Steps 3 through 6, and NHDOT will beresponsible for Steps 7 and 8 of the RSA process. The presentation given at the start-up meeting isincluded in Appendix D and the sign in sheet for the meeting is included in Appendix E.

Figure 1 – RSA Process

The RSA Team met on February 12, 2013 at the Swanzey Town Hall to conduct the start-up meeting,perform a field review, conduct a risk assessment and identify possible solutions (steps 3-5). The agendawas as follows:

1. Presentation of the RSA process, scope, and objectives to the RSA Team;2. Present background information on project area;3. Group discussion on safety issues and concerns;4. Field review at project site;5. Discussion of site observations, risk assessment, and possible solutions;6. Discussion of next steps.

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III. Background Information:

The Town of Swanzey is located in the southwestern portion of New Hampshire. It is the second largestcommunity in Cheshire County with a population of 7,230.1 It borders the City of Keene and hosts theregional airport, fairgrounds, industrial and commercial development as well as the regional middle andhigh school. The main arteries through town consist of Route 10 and 12 which run diagonally throughtown to the City of Keene as shown in Figure 2.

NH 32 (also called Old Homestead Hwy) provides a north-south link between the towns of Richmondand Swanzey to the City of Keene and is classified as a major collector. Sawyers Crossing Road is a localroad that runs east-west over a historic covered bridge. The map shows the location of the subjectintersection as a red circle and traffic count locations shown as blue dots. Both NH 32 and SawyersCrossing Road are maintained by NHDOT.

Figure 2 - Overview of study location

1 2010 Census.

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Historically, the Town of Swanzey was an industrious town with many mills, resource extractionoperations, hydropower plants, factories, rail access, and agricultural operations. Starting in the 1960’sthe town started evolving into a low density bedroom community.2 Its population density has grownfrom 115 persons/square mile in 1980 to 160 persons/square mile in 2010.3 The Town of Swanzeyvalues its rural character and has aimed to preserve its natural and historic resources, while at the sametime accommodating change and growth.4

Growth pressure from the City of Keene has caused commercial, residential, and light-industrialdevelopment in the northern portion of the town. Accordingly, traffic counts have increased as regionalcommerce and employment opportunities have expanded in the City of Keene. From 1994 to 2004,traffic on NH 32 at the intersection grew an average of 3.5% per year. However, traffic growth from2004 to 2010 decreased on average of 1% per year.5 It is generally accepted by town officials andplanners that continued regional commercial growth in the Winchester St. (NH 10) area of Keene (seehighlighted area in Figure 2) will continue to cause increased traffic impacts upon the study intersection.

IV. NH 32/Sawyers Crossing Road Intersection

The intersection is located equidistant from Routes 10 and 12 and provides a split for traffic heading tothe City of Keene. Figure 3 shows an aerial photo of the intersection as well as the locations of varioustraffic control and traffic warning signs in this vicinity. The intersection is configured as a large splitterisland and has been in place for as long as any of the RSA team-members can remember.

The intersection is also located at the epicenter of municipal and institutional services for the area. TheCarpenter Home for the elderly, the middle and high schools, town offices, library, fire department, andSAU 93 offices are all located around the intersection.

A key aspect to the pedestrian and vehicle traffic at the intersection is the location of the Mt. CaesarElementary School and the Monadnock Regional High School. The two schools function as one largecampus divided by NH 32. High school students frequently cross the road to access athletic fieldslocated at the Mt. Caesar School. In cases of emergency, Mt. Caesar students are evacuated to the HighSchool and cross the road with assistance from the fire/police department. Traffic patterns are alsoinfluenced by the internal circulation and the entry/exit points of the school’s parking lots.

Currently, Mt. Caesar School traffic flows in one direction - entering from NH 32 and exiting ontoSawyers Crossing Road. The High School traffic has a one-way entrance located about 100 feet from theintersection; a double-exit [to allow traffic to exit either northbound or southbound] north of the one-way entrance; and an entrance/exit at the far northerly end of the property.

This intersection is also designated as an Access Control Point for the Vermont Yankee TrafficManagement Plan. In case of an emergency at the nuclear power plant this intersection would bestaffed by emergency personnel to divert traffic from traveling south into the evacuation zone.

2 Swanzey Master Plan Update 2003, Town of Swanzey, pg. 24.3 Town of Swanzey has an area of 45 square miles and a population of 5,183 in 1980 and 7,230 in 2010 accordingto the US Census Bureau.4 Swanzey Master Plan Update 2003, Town of Swanzey, pg. 4.5 Traffic counts provided by SWRPC for counters 441054, 441064, 441065.

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Figure 3 - Project Location Map

V. Traffic Data

NH 32 has an average daily traffic count of 4,500 vehicles per day (vpd) in this area.6 Traffic countsconducted by SWRPC during April 2012 show 4,754 vpd south of the intersection and 4,396 vpd north ofthe intersection. SWRPC also conducted a traffic count on Sawyers Crossing Road at the covered bridgethat showed a count of 3,465 vpd.

The Southwest Regional Planning Commission (SWRPC) also conducted turning movement counts at theintersection on April 4-5, 2012. The peak hours at the intersection are from 7:00 to 8:00 AM (729vehicles/hour) and anywhere from 2:15 to 4:45 PM (avg. 694 vehicles/hour). The turning movementcount data is included in Appendix A and a graphical summary of the data is shown in Figure 4 andFigure 5 below.

6 Traffic Count reported by NHDOT 2010 on NH 32 over S. Branch of Ashuelot (station 441054).

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Figure 4 - AM Peak Hour Counts

Figure 5 - PM Peak Hour Counts

Peak Morning Hour7:00 – 8:00 AM NH 32 Northbound

228(31%)

183(25%)

NH 32 Southbound

38(5%)

80(11%)

STOP

SawyersCrossingEastbound

43(6%)

157(22%)

STOP

Peak Afternoon Hour3:45 – 4:45 AM

STOP NH 32 Northbound

92(13%)

94(14%)

NH 32 Southbound

129(19%)

143(21%)

STOP

SawyersCrossingEastbound

137(20%)

99(14%)

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VI. Crash Data

Crash data from 2000 to 2011 for the study intersection was summarized by SWRPC and is included inAppendix B. There were a total of 20 multi-vehicle crashes and 1 single vehicle crash. Although therewere no fatalities, 11 of the crashes resulted in injuries. Figure 6 shows the collision diagram – crasheswith circles designate an injury. A summary of crash data is as follows:

21 total crashes (avg. 1.75 crashes per year)No fatalities, 11 injury, 10 Property Damage Only (PDO)1 crash involved fixed objects/run off the road0 crashes involving bicyclist/pedestrian5 rear end crashes on NH 32 northbound2 rear end crashes on NH 32 southbound70% of crashes during daylight85% crashes involve NH 32 northbound traffic52% of total crashes and 54% of injury crashes involve vehicles turning onto Sawyers Crossingfrom NH 32 northbound.

These crashes can be categorized as medium speed crashes, usually involving vehicles traveling 35-40mph. Table 1 shows how severity ratings for crash type are measured. Crashes at this intersection canbe classified as moderate to high severity due to the type of accident and injuries.

Table 1 - Crash Severity Ratings

TYPICAL CRASHES EXPECTED(per RSA item) EXPECTED CRASH SEVERITY SEVERITY RATING

crashes involving high speeds or heavyvehicles, pedestrians, or bicycles

probable fatality orincapacitating injury

Extreme

crashes involving medium to high speed;head-on, crossing, or off-road crashes

moderate to severe injury High

crashes involving medium to low speeds;left-turn and right-turn crashes

minor to moderate injury Moderate

crashes involving low to medium speeds;rear-end or sideswipe crashes

property damage only orminor injury

Low

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Figure 6 - Crash Data

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Table 2 - Risk Ratings

Low Moderate High ExtremeFrequent >10 per year C D E FOccasional 1-9 per year B C D EInfrequent >1 per 5 years A B C DRare <1 per 5 years A A B CCrash Risk Ratings: A: lowest risk E: high risk

B: low risk F: highest risk

CRASH FREQUENCY RATING SEVERITY RATING

C: moderate-low riskD: moderate-high risk

Based on the crash data, crash types can be summarized based on their severity rating (from Table 1)and from their frequency (from Table 2). Combining these factors reveals the risk-rating for each crashtype at this intersection (see Table 3 below). The RSA team confirmed that the highest risk occurs atthe southern leg of the intersection.

Table 3 - Crash Severity

Type of CrashCrashes

/year SeveritySeverityRating Frequency

RiskRating

Right-Angle Crashesat southern leg ofintersection

0.42 PDO0.5 Injury

Moderateto severeinjury

High Occasional Moderate-High risklevel

Rear-end crashes onNH 32

0.33 PDO0.33 Injury

Minor tomoderateinjury

Moderate Infrequent Low risklevel

Vehicles turning outof Sawyers CrossingRd hit vehicles onNH 32

0.17 PDO Minor tomoderateinjury

Moderate Rare Lowestrisk level

VII. Stakeholder Identified Risk Factors:

A field visit was conducted between 10:00 and 11:00 AM on February 12, 2013. The weather was cooland overcast. There was a considerable amount of snow on the ground due to the previous week’sblizzard (note that the pictures below were taken prior to the blizzard). The RSA Team was providedwith a list of possible safety issues to consider during their inspection. As a result of this site visit anddiscussions during the start-up meeting, the following risk factors were identified for NH 32/SawyersCrossing Road Intersection:

A. Right-of-way Confusion: There is driver confusion as to who has the right-of-way at thesouthern leg of the intersection. Traffic traveling northbound on NH 32 sometimescrosses the southbound lane of NH 32 onto Sawyers Crossing Road without yielding toopposing traffic.

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Figure 7 - Southern leg of intersection

B. Tree Hazard: The large pine tree in the middle of the splitter island is exposed andwould pose a hazard if it fell.

Figure 8 – NH 32 northbound at southern part of intersection

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C. Sight Line Issues: The newly planted trees along the southeastern side of theintersection may pose a sight distance problem once they mature.

D. Sign Clutter: There are a lot of distractions at the intersection including warning,regulatory, and directional signs.

Figure 9 – Signage on splitter island

E. Simeneau Lane: Simeneau Lane, which is the access road for the Carpenter Home, islocated at the southern leg of the intersection and creates an extra conflict point.

F. Potholes: There is a large pothole on the southern leg of the intersection which mayforce vehicles to stop in the wrong part of the intersection.

G. Gridlock in front of schools: The entrance to the high school and the entrance to theelementary school are offset by about 150 feet and on opposite sides of the road. Thiscan cause gridlock when queues form behind vehicles trying to access each parking lotand block the opposite entrance. The RSA team reported that there are occasional rear-end crashes in front of the schools.

H. Access Management: There are various access points on the southern approach to theintersections for the town library, town hall and SAU offices. These curb cuts are notwell defined and create a very wide continuous asphalt access point. Theseunconstrained curb cuts add to the confusion and clutter of the intersection.

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Figure 10 – NH 32 southbound at second High School access point

I. Lack of Curve Delineation: There are no chevrons around the curve between thesouthern and northern leg of the intersection to delineate the curve. The curve itself isnot sharp, but the lack of delineation makes it difficult for the motorist to determinewhich road is the main road.

J. Faded Pedestrian Markings: The sidewalk and crosswalk pavement markings are faded.There is an overall sense that pedestrian safety should be improved in the intersectiondue to the high number of children in the area.

K. Sign Misplacement: There is a stop-ahead sign on NH 32 southbound associated with astop sign on Sawyers Crossing Road. This sign creates confusion for motorists because itimplies that NH 32 veers to the right or that there is a stop sign on NH 32. There is alsoa deer crossing sign at the intersection which could be relocated.

L. Traffic Speed: There is concern that traffic speeds are too high in this area due to thedesign of the road. Currently the police department enforces the speed limits in front ofthe school. The speed statistics included in Appendix C show that between 78% and85% of traffic exceeds the 30 mph speed limit, with an 85th percentile speed limit ofbetween 38 and 40 mph. This means the average motorist travels through thisintersection at about 40 mph.

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Figure 11 – Sawyers Crossing Road turning left to drop children off at elementary school

Figure 12 – Speed limit reduces from 30mph to 20mph on all approaches

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VIII. Risk Analysis and Mitigation Strategies:

After determining the Crash Severity Ratings and identifying Risk Factors which may be attributing tothese crashes, Risk Factors are associated with each type of crash.

Table 4 - Risk Analysis

Type of CrashCrash Risk

RatingContributing Risk Factor

Right-AngleCrashes atsouthern leg ofintersection

Moderate-Highrisk level

A B C D E F

G H I J K L

Rear-endcrashes on NH32

Low risk level A B C D E F

G H I J K L

Vehicles turningout of SawyersCrossing Rd hitvehicles on NH32

Lowest risklevel

A B C D E F

G H I J K L

From the risk analysis table above, it can be determined which Risk Factors are most attributable tocrashes. For example, Risk Factor A, D, and L are highlighted multiple times and therefore ranked as thehighest risk factors at this intersection. On the other hand, risk factors B, C, E, F, G, H, J, and K are notdirectly attributing to existing crashes, but are safety risks nonetheless. These Risk Factors are listed aslower priorities.

Next the RSA Team brainstormed ideas on how these Risk Factors could be mitigated. All suggestionswere welcomed and considered. Each possible risk-mitigation solution was categorized as a long,medium, or short term solution based on when they could be implemented. Short term solutions couldfeasibly be accomplished within six months, medium term within six months to two years, and long termsolutions would be those that would take more than two years to implement.

The following chart summarizes the Risk Factor analysis and Mitigation Strategies that were discussed.A more detailed review of these strategies is presented in the summary section of the report.

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Table 5 - Mitigation Strategies

RiskRank Risk Factor Suggested Mitigation Strategy Timeframe

ResponsibleStakeholder

1 A. Right-of-wayconfusion

a) Realign into T-Intersectionb) Build a Roundaboutc) Realign southern leg only

a) Longb) Longc) Long

a) NHDOTb) NHDOTc) NHDOT

2 D. Sign Clutter Study placement, condition andadequacy of signage

Short NHDOT

3 L. Traffic Speeds a) Enforce speed limitb) Build a Roundabout

a) Shortb) Long

a) Townb) NHDOT

4 G. Gridlock in frontof schools

Conduct Access Management Studyto coordinate Library, Town Hall, andSAU office entrances. Also studyschool parking lot entrances andinternal circulation.

Medium SWRPC, MRSD,Town, NHDOTDistrict 45 H. Access

Management

6 I. Lack of curvedelineation

Study placement, condition andadequacy of signage

Short NHDOT

7 E. Simeneau Drive Study feasibility of making one-way Short Town8 K. Sign

MisplacementReset stop ahead sign and deercrossing signs.

Short NHDOT

9 B. Tree Hazard Remove Tree Short Town10 C. Sight Line issues Maintain sightlines by tree pruning Short MRSD/Town11 J. Faded

PedestrianMarkings

a) Repaint the crosswalksb) Conduct Safe Routes to Schoolprogram

a) Shortb) Medium

a) NHDOT/MRSDb) SWRPC/MRSD

12 F. Potholes Fix pothole Short NHDOT District 4

IX. Benefit/Cost Analysis of Improvements:

A Benefit/Cost (B/C) Analysis was performed to compare the benefits of risk mitigation strategiesidentified in Section VIII to the anticipated project cost.7 The estimated benefits will be calculated basedon the number of crashes that each mitigation strategy can prevent multiplied by the cost of that crashtype to society as shown in Table 6 - Crash Costs. The anticipated cost of constructing each safetyproject will be estimated through an engineering estimate.

7 Highway Safety Manual, pg. 7-1. 1st Edition, 2010. AASHTO

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Table 6 - Crash Costs

Collision Type Societal Crash CostFatal (K) 4,008,900$Disabling Injury (A) 216,000$Evident Injury (B) 79,000$Fatal/Injury (K/A/B) 158,200$Possible Injury (C ) 44,900$PDO (O) 7,400$Source: Crash Cost Estimates by Maximum Police-Reported InjurySeverity within Selected Crash Geometries, FHWA-HRT-05-051,October 2005

In order to estimate the number and type of crashes that will be prevented by each type of mitigationstrategies, Crash Modification Factors (CMFs) will be used. CMFs are ratios that estimate the differencebetween the numbers of crashes that will occur after the Mitigation Strategy is implemented comparedto the number of crashes that would have taken place if no improvements had been made. CMFs arelisted in a database provided by the Federal Highway Administration (FHWA) and are calculated basedon before and after studies of actual projects. For the purposes of this RSA, CMFs will be multiplied bythe number of crashes predicted in the no-build scenario to determine the number of future crashes.Each CMF also has a standard error since it is an estimate of crash reductions. The multiplication of thestandard error by 2 yields a 95% confidence interval that the true benefit is within the range calculated.8

Equation 1 – Crash Modification Factors (CMF)

Crash Reduction BY TYPE = ( (1 – CMF) +/- 2 X Std. Error) X Anticipated Crashes/Year

Total Crash Benefit = (Crash Reduction Injury X Crash Cost Injury)

+ (Crash Reduction PDO X Crash Cost PDO)

In order to compare safety mitigation options, the total costs and benefits are reduced to theirannualized basis. The annualized construction and maintenance costs of each mitigation strategy will becalculated based on its service life using the Equivalent Annual Cost (EAC) function, assuming the cost ofcapital (discount rate) to be 3%.

Equation 2 - Equivalent Annual Cost (EAC)

EAC = Discounted Investment Cost + Annual Maintenance Cost

Discounted Investment Cost/Year = Cost of Mitigation Strategy/Discount Factor

Discount Factor = ((1- (1/1+Cost of Capital)^Service Life)/Cost of Capital

= ((1-(1/1+0.03)^Service Life)/0.03

8 HSM Volume 1, p. 3-22 Table 3-3.

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An important factor in the EAC equation is the service life of the improvement. The service life of asafety improvement is limited by how long the project will be able to functionally handle traffic flows,which is measured by the Level of Service (LOS). The LOS is an indication of how long vehicles aredelayed at the intersection and ranked from LOS A (best) to LOS F (worst). In this particular intersection,there are many vehicles turning in and out of Sawyers Crossing Road. According to Figure 4 and Figure 5on page 7 only 32% to 36% of vehicles are traveling through the intersection on NH 32. The remainderof the traffic is turning. A capacity analysis of each proposed improvement will determine the servicelife. For purposes of this analysis we will assume a 3% annual growth in traffic for the area due to thecontinued development pressures as discussed in page 5.

No-Build Option

Doing nothing at this intersection is an option. Over the next 5 years, it can be expected that crasheswill continue at this intersection at the same rate as in the previous 12 years. The type and severity willbe similar as well. It is difficult to estimate crash rates and types past a 5 year window sincedevelopment patterns in this region could cause traffic patterns to fluctuate, so this analysis will notattempt to extrapolate to future years.

Based on the analysis shown on Table 3 page 10, the following estimate is made for the next 5 years:

Type of Crash Injury Crashes PDO Crashes Total CrashesRight-Angle Crashes at southern leg ofintersection

2.50 2.10 4.60

Rear-end crashes on NH 32 1.65 1.65 3.30Vehicles turning out of Sawyers CrossingRd hit vehicles on NH 32

0.00 0.85 0.85

Total for 5 year period 4.15 4.60 8.75Total per year 0.83 0.92 1.75

Average Annual Crash Costs $65,570 $6,808 $72,378

125’ Diameter – One Lane Roundabout (Option 1)

A roundabout was discussed as a possible mitigation strategy at this intersection. A roundabout wouldremove the conflicting traffic movements (Risk Factor A) and also lower traffic speeds (Risk Factor L) asshown in Table 6. A roundabout would decrease traffic speeds at the intersection from the current 40mph9 to about 20 mph due to its design. A roundabout at this intersection would reduce total crashesby 71% and injury crashes by 87% as compared to the no-build alternative. The estimated safety benefitof these reductions in crashes is $66,687 to $55,107 per year.10

9 85th Percentile speed, see Appndix C.

10 See Appendix F

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The current intersection layout is very well suited for a roundabout due to its wide right-of-way andexisting traffic flows. Based on initial reviews, a one-lane roundabout with an outside diameter of 125feet and a lane width of 18 feet fits inside the existing intersection footprint without substantiallyaffecting surrounding property, sidewalks or utilities (see plan sheet 1). For comparison purposes, theroundabout on Court St. in front of Cheshire Medical Center has a diameter of 105 feet, and the Main St.roundabout in Keene has a diameter of 150 feet.

The proposed roundabout would require reconstruction of the intersection. Roundabouts require theinstallation of curbing in order to channel vehicles into and out of the intersection. This curbing in turnrequires catch basins and pipes to remove the water from the intersection. The addition of this closeddrainage system adds significantly to the cost of construction. In addition to the drainage, constructionwould require milling of the existing pavement, repaving, and installing granite curbing for the splitterislands and any sidewalks. New signs and pavement markings would also be required, but theseincidental items would be a minor cost compared to the overall project. The estimated cost of buildingthe Roundabout is $690,000.

Based on the estimated safety benefits and construction costs, the Benefit/Cost ratio of the roundaboutoption is estimated to be between 2.08 and 1.72. (See Appendix F)

Roundabout (Option 1)

Estimated Cost Useful Lifespan Estimated Safety Benefitper Year

Benefit/CostRatio

$690,000 35 Years $66,687 - $55,107 2.08 – 1.72

A roundabout at this location should incorporate landscaping and treatments that reflect the ruralcharacter and natural beauty of the community. Also, consideration should be made to comply with anyrequirements in the Vermont Yankee Transportation Management Plans for access points.

T-Intersection Sawyers Crossing into NH 32 (Option 2)

Another suggested safety countermeasure is the realignment of the intersection into a T-intersection.This option would extend Sawyers Crossing Rd into the apex of the curve on NH 32 (see plan sheet 2).This option includes separate turning lanes to improve traffic flow. This solution would resolve variousrisk factors relating to the skew of the intersection and the confusion of vehicles traveling northboundon NH 32 turning onto Sawyers crossing road. However, it could also increase the number of rear-endaccidents at this location, would not mitigate the speeding issue, and would create more delay as thetwo legs of the intersection are merged into one.

In order to conduct the Benefit/Cost Analysis it is necessary to determine the functional life of the T-Intersection as explained in page 18 above. The maximum capacity for a T-intersection is limited by thedelay at the minor approach (Sawyers Crossing Road). An analysis of the proposed intersection shows

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that the minor approach would have a delay of 38.7 seconds (LOS E) if it was in operation today, andwould fail (LOS F) within two years. This is due to the high number of conflicting turning movements.The existing traffic flows show only 32% to 36% of traffic is through-movements on NH 32, which createsa lot of conflicting movements that would block Sawyers Crossing from making turns onto NH 32.

The T-intersection option would be cheaper to build than a roundabout (Option 1) since it would notrequire a closed drainage system, and the impacts to the existing NH 32 alignment would be minimal.The estimated cost would be about $130,000. However, as noted below the capacity of the intersectionwould fail within two years.

Even assuming a very generous Crash Modification Factor (CMF) of 0.4 for this option, the Benefit/Costratio for this option falls below 1.0 due to its short useful lifespan. (See Appendix F)

T-Intersection (Option 2)


Benefit/CostRatio

$130,000 2 years $25,565 0.38

Alternatively, re-aligning the intersection to making the NH 32 northbound traffic the minor leg (stop-controlled) would result in similar LOS for the intersection since the traffic volumes are evenlydistributed for all three approaches.

Realignment of only the southern part of the intersection (Option 3)

Another suggested safety countermeasure is the realignment of only the southern leg of theintersection into a T-intersection (see plan sheet 3). This option would result in separating SimeneauLane and would result in a total of 11 intersections or access points within a 250 foot section of road.Realigning the southern part of the intersection would remove the skew angle of the approach andreduce the confusion as to who has the right-of-way. However, it also makes the intersection morecomplicated and confusing by bringing the southern and northern legs of the intersection closertogether.

Realign Southern Leg (Option 3)


Benefit/CostRatio

$80,000 10 years $9,378 0.91

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X. Audit Response:

Submission of this report represents completion of Steps 1 through 6 of the RSA process. Thereport’s finding and recommendations will be presented to the State of NH Department ofTransportation Front Office (NHDOT FO), the Town of Swanzey Board of Selectmen, and theHighway Safety Improvement Program Committee (HSIP Committee). Each of these groupsmust support the same recommendations for a project to move forward. Each group may:

NHDOT, as the project owner, will be the first to receive this report for presentation to theFront Office. The Front Office will prepare a formal response addressing the audit findings. Theresponse will outline what actions the owner will take related to each safety concern listed inthe report along with a proposed timeline. NHDOT may either:

Agree with the suggestion described by the audit team and commit to itsimplementation outlining a schedule for the completion of the suggestion;Disagree with the suggestion described by the audit team and commit to an alternative,outlining a schedule for the completion of the alternative. In doing so, the ownershould provide a valid reason as to why they choose not to adopt the audit team’ssuggestions;Choose not to implement certain improvements at all due to financial constraints ordisagreement regarding the safety issue, believing that there is no increased riskassociated with the concern raised by the audit team. In doing so, the owner shoulddocument the reasoning behind their decision.

The NHDOT and SWRPC will then present the Front Office recommendations to the Town ofSwanzey Board of Selectmen for concurrence with the findings. The Board of Selectmen willprepare a formal response in the form of a letter which identifies which options they support.

The RSA recommendations will then be presented to the HSIP Committee for final approval andcreation of a project. Once a project is created, funding sources will be identified andobligated, and preliminary design begins.

It is important to understand that the RSA recommendations will not be implemented unless allof the above mentioned bodies concur.

Appendix A – Turning Movement Counts

Left Thru Right Peds Left Thru Right Peds Left Thru Right Peds Totals6:00 0 0 7 0 12 14 0 0 4 0 1 1 386:15 0 3 4 0 24 20 0 0 9 0 2 1 626:30 0 3 6 0 28 32 0 0 17 0 8 0 946:45 0 4 15 0 40 36 0 0 21 0 19 0 1357:00 0 15 21 0 38 81 0 1 57 0 17 0 2297:15 0 10 30 0 47 71 0 0 41 0 12 0 2117:30 0 8 15 0 46 45 0 0 23 0 6 0 1437:45 0 5 14 0 52 31 0 0 36 0 8 0 1468:00 0 11 23 0 29 42 0 0 49 0 10 0 1648:15 0 7 20 1 24 34 0 0 52 0 13 0 1508:30 0 11 9 0 23 23 0 0 22 0 17 0 1058:45 0 9 9 0 16 19 0 0 25 0 19 0 97

Totals 0 86 173 1 379 448 0 1 356 0 132 2 1574

NH 32 Southbound NH 32 Northbound Sawyer's Crossing Eastbound

Left Thru Right Peds Left Thru Right Peds Left Thru Right Peds Totals2:00 0 13 13 0 17 19 0 0 29 0 19 0 1102:15 0 41 54 0 35 21 0 0 27 0 29 0 2072:30 0 15 28 0 43 17 0 0 22 0 21 4 1462:45 0 20 16 0 20 25 0 0 20 0 18 0 1193:00 0 26 26 0 28 22 0 0 41 0 37 0 1803:15 0 37 35 1 17 15 0 1 33 0 35 3 1723:30 0 27 29 0 21 23 0 0 26 0 36 0 1623:45 0 37 21 0 21 23 0 0 23 0 45 0 1704:00 0 29 55 1 29 20 0 2 25 0 30 0 1884:15 0 30 34 2 21 26 0 0 21 0 34 0 1664:30 0 33 33 0 23 23 0 0 30 0 28 0 1704:45 0 41 22 0 21 14 0 0 15 0 48 0 1615:00 0 31 30 1 31 16 0 0 25 0 34 0 1675:15 0 37 33 0 18 8 0 0 25 0 52 0 1735:30 0 38 22 0 27 16 0 0 17 0 58 1 1785:45 0 29 28 0 24 16 0 0 19 0 51 1 167

Totals 0 484 479 5 396 304 0 3 398 0 575 9 2636

NH 32 Southbound NH 32 Northbound Sawyer's Crossing Eastbound

Appendix B – Collision Diagrams

SYMBOLS

NH 32

Town: SwanzeyPrepared by: Southwest Region Planning CommissionDate: August 17, 2012Period: January 2000 to October 2011Information Reported by Accident: Date – Time – Day of Week – Accident Report Number

Out of Control

Rear-end CollisionNumber of peoplewith reported injuriesbased on policereport or for whomambulance serviceswere rendered

Fixed Object

Left Turn

Right Turn

Intersection of Old Homestead Hwy (NH 32),Sawyers Crossing Rd

Sawyers Crossing Rd

02/04/2011 14:35 Fri 11A-011

10/17/2010 12:12 Sun 10A-078

10/01/2011 20:49 Sat 11A-070

08/28/2009 16:44 Fri 09A-077

04/15/2000 19:42 Sat 00A-042

06/26/2003 17:06 Thu 03A-071

01/09/2008 12:35 Wed 08A-001

03/18/2005 19:22 Fri 05A-037

10/10/2000 17:07 Tue 00A-101

06/13/2011 07:20 Mon 11A-048

12/10/2004 16:35 Fri 04A-122

03/30/2003 20:32 Sun 03A-041

06/22/2003 13:27 Sun 03A-070

11/10/2000 13:38 Fri 00A-114

06/30/2008 17:45 Mon 08A-043

12/05/2001 18:09 Wed 01A-102

09/01/2000 20:02 Fri 00A-089

11/17/2004 15:49 Wed 04A-113

05/09/2006 07:24 Tues 06A-053

09/29/2006 16:47 Fri 06A-098

03/17/2006 19:24 Fri 06A-037

Appendix C – Speed Data

SpeedStatHour-9 Page 1

Speed Statistics by Hour SpeedStatHour-9Site: 2.0.0NS Description: NH 32 Between Monadnock High School and BridgeFilter time: 11:27 Monday, April 02, 2012 => 10:28 Monday, April 09, 2012 Scheme: Vehicle classification (Scheme F2)Filter: Cls(1 2 3 4 5 6 7 8 9 10 11 12 13 ) Dir(NESW) Sp(6,99) Headway(>0)

Vehicles = 28344Posted speed limit = 30 mph, Exceeding = 24040 (84.82%), Mean Exceeding = 36.82 mphMaximum = 70.2 mph, Minimum = 6.7 mph, Mean = 35.2 mph85% Speed = 40.3 mph, 95% Speed = 43.2 mph, Median = 35.3 mph12 mph Pace = 30 - 42, Number in Pace = 21759 (76.77%)Variance = 28.69, Standard Deviation = 5.36 mph

Hour Bins (Partial days)

Time | Bin | Min | Max | Mean | Median | 85% | 95% | >PSL |

| | | | | | | | 30 mph |

| | | | | | | | |

0000 | 117 0.4% | 27.7 | 47.9 | 35.9 | 35.6 | 40.0 | 41.6 | 110 94.0% |

0100 | 48 0.2% | 28.2 | 51.1 | 36.6 | 35.3 | 40.7 | 45.9 | 44 91.7% |

0200 | 40 0.1% | 23.3 | 43.2 | 36.4 | 36.7 | 41.8 | 42.9 | 37 92.5% |

0300 | 25 0.1% | 27.3 | 44.8 | 36.5 | 37.6 | 41.2 | 42.3 | 20 80.0% |

0400 | 79 0.3% | 27.2 | 58.0 | 38.2 | 38.3 | 43.2 | 45.4 | 76 96.2% |

0500 | 281 1.0% | 26.1 | 53.2 | 37.3 | 37.1 | 41.8 | 44.7 | 264 94.0% |

0600 | 1036 3.7% | 18.3 | 51.7 | 34.6 | 34.7 | 39.8 | 43.2 | 835 80.6% |

0700 | 2252 7.9% | 9.6 | 60.4 | 31.3 | 31.5 | 37.4 | 40.7 | 1335 59.3% |

0800 | 1650 5.8% | 6.7 | 60.8 | 34.0 | 34.2 | 39.4 | 42.5 | 1300 78.8% |

0900 | 1551 5.5% | 15.3 | 57.1 | 36.1 | 36.0 | 40.5 | 43.2 | 1432 92.3% |

1000 | 1563 5.5% | 18.0 | 56.7 | 36.5 | 36.5 | 40.7 | 43.6 | 1460 93.4% |

1100 | 1620 5.7% | 12.9 | 51.9 | 36.4 | 36.2 | 40.9 | 43.8 | 1486 91.7% |

1200 | 2072 7.3% | 14.7 | 53.5 | 36.4 | 36.5 | 40.5 | 43.2 | 1926 93.0% |

1300 | 1662 5.9% | 11.7 | 60.6 | 36.4 | 36.2 | 40.9 | 44.1 | 1514 91.1% |

1400 | 2243 7.9% | 10.8 | 55.6 | 33.3 | 33.3 | 39.1 | 42.7 | 1572 70.1% |

1500 | 2499 8.8% | 11.7 | 58.1 | 33.0 | 33.3 | 39.4 | 42.3 | 1732 69.3% |

1600 | 2536 8.9% | 16.9 | 63.3 | 36.0 | 36.0 | 40.7 | 43.6 | 2263 89.2% |

1700 | 2288 8.1% | 19.1 | 70.2 | 37.0 | 36.9 | 41.2 | 43.6 | 2200 96.2% |

1800 | 1739 6.1% | 16.2 | 68.7 | 36.9 | 36.7 | 41.2 | 44.1 | 1627 93.6% |

1900 | 1161 4.1% | 21.2 | 54.8 | 36.1 | 36.0 | 40.0 | 43.2 | 1101 94.8% |

2000 | 875 3.1% | 22.1 | 54.1 | 35.8 | 35.6 | 40.3 | 42.9 | 807 92.2% |

2100 | 478 1.7% | 22.0 | 57.5 | 35.6 | 35.3 | 40.0 | 42.1 | 441 92.3% |

2200 | 351 1.2% | 20.1 | 70.0 | 35.3 | 34.7 | 40.3 | 44.1 | 302 86.0% |

2300 | 178 0.6% | 22.3 | 62.1 | 35.5 | 34.9 | 40.5 | 44.1 | 156 87.6% |

---- | 28344 100.0% | 6.7 | 70.2 | 35.2 | 35.3 | 40.3 | 43.2 | 24040 84.8% |



Speed Statistics by Hour SpeedStatHour-10Site: 1.0.0NS Description: NH32 in front of Swanzey Town OfficesFilter time: 11:00 Monday, April 02, 2012 => 10:19 Monday, April 09, 2012 Scheme: Vehicle classification (Scheme F2)Filter: Cls(1 2 3 4 5 6 7 8 9 10 11 12 13 ) Dir(NESW) Sp(6,99) Headway(>0)

Vehicles = 31646Posted speed limit = 30 mph, Exceeding = 24655 (77.91%), Mean Exceeding = 35.18 mphMaximum = 54.8 mph, Minimum = 6.9 mph, Mean = 33.3 mph85% Speed = 38.0 mph, 95% Speed = 40.7 mph, Median = 33.3 mph12 mph Pace = 28 - 40, Number in Pace = 25511 (80.61%)Variance = 23.30, Standard Deviation = 4.83 mph

Hour Bins (Partial days)

Time | Bin | Min | Max | Mean | Median | 85% | 95% | >PSL |

| | | | | | | | 30 mph |

| | | | | | | | |

0000 | 138 0.4% | 21.4 | 44.0 | 34.1 | 33.6 | 38.5 | 40.9 | 116 84.1% |

0100 | 83 0.3% | 10.4 | 49.9 | 34.0 | 33.8 | 38.0 | 40.3 | 68 81.9% |

0200 | 38 0.1% | 19.9 | 40.6 | 32.2 | 32.0 | 36.2 | 38.7 | 29 76.3% |

0300 | 48 0.2% | 24.1 | 47.2 | 34.5 | 34.4 | 38.3 | 40.7 | 43 89.6% |

0400 | 88 0.3% | 25.1 | 46.8 | 34.9 | 34.7 | 38.7 | 41.6 | 77 87.5% |

0500 | 347 1.1% | 19.4 | 44.9 | 33.1 | 32.7 | 36.9 | 39.6 | 286 82.4% |

0600 | 1345 4.3% | 12.0 | 46.2 | 30.8 | 30.9 | 35.3 | 38.5 | 782 58.1% |

0700 | 2471 7.8% | 13.2 | 45.9 | 29.7 | 29.3 | 34.9 | 38.0 | 1127 45.6% |

0800 | 1789 5.7% | 15.6 | 49.0 | 31.8 | 32.0 | 36.9 | 40.0 | 1156 64.6% |

0900 | 1578 5.0% | 13.9 | 52.8 | 34.0 | 34.0 | 38.3 | 40.9 | 1322 83.8% |

1000 | 1554 4.9% | 15.6 | 50.6 | 33.8 | 34.0 | 38.0 | 40.9 | 1317 84.7% |

1100 | 1914 6.0% | 13.1 | 53.6 | 34.4 | 34.4 | 38.5 | 41.4 | 1650 86.2% |

1200 | 2073 6.6% | 9.8 | 53.4 | 34.1 | 34.0 | 38.5 | 41.2 | 1776 85.7% |

1300 | 1882 5.9% | 15.7 | 52.5 | 34.1 | 34.2 | 38.3 | 40.7 | 1575 83.7% |

1400 | 2147 6.8% | 11.7 | 48.6 | 32.4 | 32.7 | 37.8 | 40.5 | 1510 70.3% |

1500 | 2562 8.1% | 6.9 | 50.6 | 32.3 | 32.4 | 37.1 | 40.0 | 1785 69.7% |

1600 | 2717 8.6% | 9.7 | 48.9 | 34.2 | 34.2 | 38.5 | 41.2 | 2301 84.7% |

1700 | 2770 8.8% | 12.8 | 49.6 | 34.9 | 34.9 | 38.7 | 41.6 | 2487 89.8% |

1800 | 2180 6.9% | 14.0 | 50.0 | 34.6 | 34.4 | 38.7 | 41.2 | 1935 88.8% |

1900 | 1495 4.7% | 15.7 | 50.3 | 34.0 | 34.0 | 38.0 | 40.5 | 1278 85.5% |

2000 | 1055 3.3% | 17.7 | 46.6 | 33.7 | 33.6 | 37.6 | 39.6 | 898 85.1% |

2100 | 668 2.1% | 20.5 | 54.8 | 33.6 | 33.1 | 37.6 | 40.5 | 551 82.5% |

2200 | 425 1.3% | 20.3 | 49.5 | 33.7 | 33.6 | 37.6 | 40.3 | 351 82.6% |

2300 | 279 0.9% | 17.1 | 45.3 | 33.8 | 33.3 | 38.0 | 39.8 | 235 84.2% |

---- | 31646 100.0% | 6.9 | 54.8 | 33.3 | 33.3 | 38.0 | 40.7 | 24655 77.9% |


Appendix D – RSA Presentation

INTERSECTION OF

OLD HOMESTEAD HWY (NH 32) &

SAWYERS CROSSING RD

TOWN OF SWANZEY

ROAD SAFETY AUDIT

Agenda

Time Item

9:00-9:05 Welcome and Introductions

9:05-9:15 Presentation on the RSA process, scope andobjectives

9:15-9:30 Background information on project area

9:30-10:00 Group discussion on safety issues and concerns

10:00-10:30 Field Review at project site

10:30-11:30 Return to meeting room – discussion of siteobservations

11:30-12:00 Discussion of next steps and conclusion of meeting

Introductions

PresenterNicolas Bosonetto– CHA

StakeholdersTown of Swanzey

Monadnock School District

Southwest Regional Planning Commission

NHDOT

Road Safety Audit

A Road Safety Audit (RSA) is a formal safety performanceevaluation.

Conducted by independent, multi-disciplinary RSA Team.

Goal is to enhance safety for all road users, under allweather conditions.

RSAs follow an eight step process.

Outcome is a report identifying short, medium and longterm solutions.

Projects are created once DOT, Town, and HSIP Committeereach consensus.

RSA Process

Step 1 – Identify Project

Town submits RSA Application to NHDOT

Compile Data – typically RPCResearch accident data

Conduct traffic counts

Gather Historical Information on Project AreaWhat has been done here before?

Identification of stakeholders

Step 2 – Select RSA Team

Step 3 – Conduct Start-Up Meeting

Step 3 – Conduct Start-Up Meeting

Goals:Project Overview / review of project scope

Review project traffic data

Review project accident data

Review history of efforts

Gather institutional knowledge from Stakeholders

Project Overview

Project Area

Traffic Counts – NH 32 / Sawyers Crossing Rd

Annual Average Daily Traffic (ADT)NH 32 (Town Hall) – 4,754 vehicles per day in April 2012

NH 32 (N. of school) – 4,396 vehicles per day in April 2012

Sawyers Crossing– 3,465 vehicles per day in Aug. 2011

Traffic PatternsSchool related traffic

Growth of regional commercial center in west Keene

School Functions


Turning Movement Counts April 4-5, 2012Morning Peak Hour 7:00 – 8:00

Volume = 729 vehicles/hourPeak 7:00 – 7:15 = 229 vehiclesPHF = 0.80

Afternoon Peak from 2:15 – 4:45Avg. Volume = 690 vehicles/hourPeak 2:15 – 2:30 = 207 vehiclesPHF = 0.83

17 pedestrians counted in PM32% of traffic is through on NH 3235% use southern leg of intersection33% use northern leg of intersection

NH 32 / Sawyers Crossing RdCollision Diagram 2000 - 2011

NH 32 / Sawyers Crossing RdAccident Data 2000 - 2011

20 total accidents involving 2 vehicles1 other crash involved vehicle running off-road andnot counted in analysis.

10 injury, 0 fatalities, 10 PDO

70% during daylight

55% right angle crashes

35% involve rear-end collisions

85% involve northbound traffic

No accidents involving peds/bikes

Review Project History

Review history of intersectionSafety Issues

Swanzey Police Chief Eric Sargent expressed concern regardingNH 32 northbound traffic turning left onto Sawyers Crossing in1999

Previous improvementsNHDOT changed yield signs to stop signs in 1999

SWRPC Meeting in 2012Introduction to RSA Process

Institutional Knowledge from Stakeholders

Step 4 – Field Review

Step 4 – Field Review

GoalsObserve existing conditions

Identify/verify safety concerns

Things to consider - GOREGeometric attributes and condition of roadway

Operations - Traffic movements, signs, pavementmarkings, lighting

Road Users - All possible users and their needs

Environment - effect of weather, vegetation and flooding

Field Review – Focus Items

Traffic patternsVehicle

Pedestrian - school students

Location & condition of crosswalks & sidewalks

Sign locations, type, condition

Sight lines for approaching vehicles

Geometry of all approaches (skews, lane widths, etc.)

Right of Way considerations

Access points & conflict points

Lighting needs

Maintenance issues

Step 4 - Field Review

Stay Together as a GroupPromote Group Discussion

Safety FirstRecommend wearing safety vest

Be careful of traffic, roadside ditches, culverts, manholes andvegetation

Do not block sight lines of vehicles attempting to use intersection

Be careful of rocks kicked up by passing trucks

LogisticsReturn to Meeting Room

Step 5 – Conduct Analysis


1. Identify Safety RisksUse checklist and notes from discussions & field visit

2. Prioritize RisksCategorize each safety risk from Low to High

Consider:Frequency of crashes

Type of crashes

Severity of injuries

Speed of vehicles involved

Type of user involved (children, pedestrians, trucks, etc…)


3. Brainstorm possible solutionsAll suggestions are welcomed

Use team members as resources for engineering, enforcement,policy, and education knowledge

Identify solutions as short, medium, and long term implementation

Identify Stakeholder responsible for each solution

Step 5 – Prepare Report

CHA will prepare report based on today’s meeting

Draft Report will be circulated to RSA Team

Comments will be incorporated into Final Report

Final Report will be submitted to NHDOT

Preliminary sketches and benefit/cost analysis will beprepared to supplement Final Report and presentation.

Step 6 – Present Findings to NHDOT

Step 7 –Prepare Formal Response

The following three entities must support final solution(s)

NHDOT Front Office

Municipality

Highway Safety Improvement Program (HSIP)Committee

Project scheduled, funded and designed

Project is constructed

Step 8 – Incorporate Findings

Thank you

Questions/Comments

Nicolas Bosonetto – [email protected]

mailto:[email protected]

Appendix E – RSA Sign-in Sheet

Appendix F – B/C Analysis

Appendix F – Pg. 1

Roundabout (Option 1) B/C Calculations

a) Safety Benefits

A roundabout has a Crash Modification Factor (CMF) of 0.29 for all crashes and 0.13 for injury crasheswith a standard error of 0.04.11 A roundabout achieves these safety improvements by reducing thenumber of conflict points and reducing speeds. There is no CMF for PDO crashes, therefore PDO benefitwill be calculated by subtracting Injury from Total crashes. Applying these factors to expected crashes atthe intersection on a per year basis:

Total Crash Reduction = ((1-0.29) +/- 2 X 0.04) X 1.75 Total crashes/yr = 1.38 to 1.10 crashes/yr

Injury Crash Reduction = ((1-0.13) +/- 2 X 0.04) X 0.83 Injury crashes = 0.79 to 0.66 crashes/yr

PDO Crash Reduction = Total Crash Reduction – Injury Crash Reduction = 0.59 to 0.45 crashes/yr

Total Highest Benefit = (0.79 X $79,000) + (0.59 X $7,400) = $66,687/yr

Total Lowest Benefit = (0.66 X $79,000) + (0.45 X $7,400) = $55,107/yr

b) Capacity/Lifespan

The maximum capacity for a single-lane roundabout can best be estimated as 1,800 veh/hour.12 Thepeak turning movement counts at this intersection were between 694 and 729 veh/hour. At a growthrate of 3%, a single lane roundabout would have a design life of at least 35 years before trafficcongestion would become an issue.

c) Construction Costs

For estimating purposes, the actual costs for the Maple Street Roundabout in Keene, NH will be used.That roundabout was designed by CHA, Inc. and recently completed as a municipally managed HSIPproject and is similar enough to the proposed roundabout to provide a comparison. One maindifference is that the Maple St. roundabout has four legs, whereas this proposed roundabout only hasthree. Underground utilities were also an issue with the Maple St. roundabout, whereas they are notpresent at the study intersection.

Conservatively estimating the differences between the Maple St. and proposed roundabout would resultin a 5% difference in estimated costs.

11 HSM, Table 14-4.

12 Roundabouts: An Informational Guide, FHWA Publication No. FHWA-RD-00-067.http://www.fhwa.dot.gov/publications/research/safety/00067/000674.pdf

http://www.fhwa.dot.gov/publications/research/safety/00067/000674.pdf


Table 7 - Maple Street Roundabout Costs

Item Description Total Cost TimeframeEngineering Survey, design, quantities, bid

packages$73,800 10 Months

Construction Building of the roundabout, trafficcontrol, closed drainage system, etc…

$586,550 9 Months

ConstructionInspection

Inspection of construction to assurequality

$65,000 Concurrent withconstruction

Maple St. Roundabout Total $725,350 About 2 YearsOption 1 Estimate

(-5% adjustment for three legs andutilities)

$690,000

Using this cost estimate, a roundabout for this location would cost about $690,000 to build. It isassumed that the maintenance costs are the same, since the roundabout and the current intersectionhave similar layouts, including a landscaped center.

Assuming the roundabout has a lifespan of 35 years, the cost amounts to $29,569 per year.

Discount Factor = ((1-(1/1+0.03)^35)/0.03 = 21.49

Discounted Investment Cost/Year = $690,000/21.49 = $32,112

EAC = $32,112

d) B/C Ratio

The annual Benefit/Cost Ratio of the roundabout alternative is therefore the yearly benefit divided bythe yearly cost.

$66,648 to $56,160/$32,112 = 2.08 to 1.72


T-Intersection (Option 2) B/C Calculations

a) Safety Benefits

The safety benefits of consolidating the splitter-island intersection into a T-intersection would mainly berelated to the removal of the skew of the southern leg of the intersection. This option would notmitigate other risk factors such as speed and sight lines issues.

Currently, the skew of the southern leg of the intersection is about 56 degrees. Realigning it wouldeliminate the skews and provide more sight distance. The CMF for increasing the skew is calculated bythe equation:

CMFskew = e^(0.0040xskew) (eq. 14-1 HSM pg. 14-17)

CMF56=e^(0.0040x56) = 1.25

CMF0=e^(0.0040x0) = 1.0

CMF = 1.0/1.25 = 0.8

The skew CMF should only be applied to the accidents occurring at the southern leg of the intersection,because this option would not mitigate other risk factors. However it appears that this CMF does notfully consider the reduction in accidents due to the confusion of the Y-intersection for NH 32northbound traffic. This CMF will therefore be doubled to 0.4, meaning that existing crashes will bereduced by 60%. Also, this CMF does not provide a standard deviation.

Injury Crash Reduction = (1-0.4) X 0.5 Injury crashes = 0.30 crashes/yr

PDO Crash Reduction = (1-0.4) X 0.42 Total crashes/yr = 0.25 crashes/yr

Total Benefit = (0.3 X $79,000) + (0.25 X $7,400) = $25,562/yr


The maximum capacity for a T-intersection is limited by the delay at the minor approach (SawyersCrossing Road) and for the left turning movement of NH 32. For purposes of this analysis, we will accepta LOS E on the minor leg as acceptable, which translates as a delay of 35 to 50 seconds per vehicle.

A capacity analysis for the T-intersection option reveals that it would operate at an LOS E with thecurrent traffic. This means that during the morning peak hour, the intersection would have a delay ofabout 39 seconds per vehicle attempting to turn from Sawyers Crossing Rd onto NH 32 northbound.Assuming a 3% yearly growth in traffic, the T-intersection would fail (LOS F) in 2 years. (see Figure 13below).


Figure 13 - T-Intersection Capacity Analysis – 2 years out



Realigning the intersection to a T-intersection would not require utility relocation, right-of-wayacquisition, or drainage improvements. Therefore the costs would mainly be associated withexcavation, select materials, and paving. It is assumed that the maintenance cost would be similar tothe existing intersection. A rough estimate for this project:



Construction Building of the intersection trafficcontrol, all items included

$100,000 6 Months




Total $130,000 1.5 Years

Therefore, assuming the T-intersection has a useful lifespan of 2 years, the cost amounts to $67,939 peryear.

Discount Factor = ((1-(1/1+0.03)^2)/0.03 = 1.91


EAC = $67,939

d) B/C Ratio


$25,565/$67,939 = 0.38


Re-align Southern Leg (Option 3) B/C Calculations

a) Safety Benefits

Realigning the southern leg of the intersection would realistically create a much more confusingintersection due to the close proximity of the north leg and realigned southern leg. Currently, the skewof the southern leg of the intersection is about 56 degrees. The CMF for eliminating the skew iscalculated by the equation:

CMFskew = e^(0.0040xskew) (eq. 14-1 HSM pg. 14-17)

CMF56=e^(0.0040x56) = 1.25

CMF0=e^(0.0040x0) = 1.0

CMF = 1.0/1.25 = 0.8

The skew CMF should only be applied to the accidents occurring at the southern leg of the intersection.Also, this CMF does not provide a standard deviation.

Injury Crash Reduction = (1-0.8) X 0.5 Injury crashes/yr = 0.10 crashes/yr

PDO Crash Reduction = (1-0.8) X 0.42 Total crashes/yr = 0.084 crashes/yr

Total Benefit = (0.1 X $79,000) + (0.084 X $7,400) = $8,521/yr


Due to the fact that this realignment creates a very confusing intersection arrangement, it is estimatedthat the lifespan would be at most 10 years. This limited lifespan is due mostly on the presumption thatit would not resolve the main safety issues and would add to the overall confusion of the intersection.


The costs of realigning the southern leg of the intersection would mainly be associated with excavation,select materials, and paving. It is assumed that the maintenance cost would be similar to the existingintersection. A rough estimate for this project:



Construction Building of the intersection trafficcontrol, all items included

$50,000 6 Months




Total $80,000 1.5 Years


Assuming the new alignment has a lifespan of 10 years, the cost amounts to $9,378 per year.

Discount Factor = ((1-(1/1+0.03)^10)/0.03 = 8.53


EAC = $9,378

e) B/C Ratio


$8,521/$9,378 = 0.91


Table 8 - Summary of B/C Analysis

Equivalent Annual Cost (EAC)

Factors Do Nothing Roundabout T-Intersection RealignInvestment Cost $0.00 $690,000.00 $130,000.00 $80,000.00

Expected Service Life (years) n/a 35 2 10Maintenance Costs $0.00 $0.00 $0.00 $0.00

Cost of Capital (%) 0% 3% 3% 3%

1(1+Investment Cost)

(1-v^service Life)Cost of Capital

Investment CostDiscount Factor

Injury Crashes/Yr 0.83 0.79 0.30 0.100.66

PDO Crashes/yr 0.92 0.59 0.25 0.080.45

CMF - Injury Crashes n/a 0.13 0.4 0.8

CMF - Total Crashes n/a 0.29 0.4 0.8std. Error n/a 0.04 0 0

Benefit - High End = $0.00 $66,687.10 $25,564.80 $8,521.60

Benefit - Low End = $0.00 $55,106.62 $0.00 $0.00

Benefit/Cost Ratio = n/a 2.08 0.38 0.91n/a 1.72 n/a n/a

0.9709

8.53

$9,378.44Equivalent Annual

Cost (EAC) = = $32,112.11

0.9709

1.91

$67,939.41

n/a

n/a

n/a

v = 0.9709 =

Discount Factor = = 21.49

road safety audit swanzey, new hampshire nh …...nhdot: 1. evaluate feasibility of reconfiguring...

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