assembly david levinson. induced travel s1: supply before s2: supply after price of travel quantity...
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Assembly
David Levinson
Induced TravelS1: Supply before
S2: Supply after
Price of Travel
Quantity of Travel (VMT)
Q1 Q2
P1
P2
Demand
Elasticity
• %Change in Demand / % Change in Price
• (Q/Q)/(P/P)• Typically look at a 1% change in
price when measuring change in demand, that is, try to keep it “marginal”.
Understanding Elasticity
Feature Elastic goods Inelastic goods PED value Greater than 1 Less than 1 A rise in price means A larger fall in demand A smaller fall in demand Slope of demand curve Flat Steep Number of substitutes Many Few Type of good Luxury Necessity Price of good Expensive Cheap Example Hyundai Gasoline
Types of Elasticity
• Price Elasticity of Demand (Demand Changes with Price)
• Price Elasticity of Supply (Supply Changes with Price)
• Cross Elasticity of Demand (Demand Changes with Price of Another Good)
• Income Elasticity of Demand (Demand Changes with Income).
How Highway Expansion Effects Travel and Activity
• [Round Robin]• Makes network faster, • Higher attainable speeds lead to time savings
in travel (price)• Increases accessibility• Broadens commuter’s travel choices• More non-travel activities• Individuals maximize their utility
Estimating How Much
• Price Elasticity of Demand• Capacity is surrogate for Time (or
Price)• % Change in Demand / % Change
in Capacity• Or If You Like Calculus e = dQ/dP .
ElasticitiesStudy ElasticityDowling and Colman(1995)
0.3-0.5 % i ncrease in trip generation due to congestionrelieving projects
Fulton et al. (2000) 0.2-0.6% increase in VMT due t o 1% increase in l anemiles
Hansen and Huang(1997) 0.6-0.7% increase in VMT due t o 1% increase in l anemiles (County Level)0.9% increase in VMT due to 1% increase in lane miles(Metropolitan Level)
Noland (1999) 0.2-0.5% increase in VMT due t o 1% increase in l anemiles(Short run estimates)0.7-1.0% increase in VMT due t o 1% increase in l anemiles (Long run estimates)
Strathman et al. (2000) 0.29% direct effect for 1%increase in road capacity0.033% indirect effect for 10% increase in road capacity
Induced Demand: A Microscopic Approach
• Measure Extent of Induced Demand due to Roadway Expansions (Not New Roads)
• Use Data on Twin Cities Links Over 20 Years
Capacity Growth in Twin Cities
Summary of Lane miles
0
500
1000
1500
2000
1976 1980 1984 1988 1992 1996 2000
Year
Lane miles
Interstates Trunk Highways Hennepin County Highways
1995 Road Network Used in Analysis
Interstates Trunk Highways Hennepin CountyHighways (CSAH)
Number oflinks
Total linklength(Kms)
Number oflinks
Total linklength(Kms)
Number oflinks
Total linklength(Kms)
Total 1193 710 2138 1808 1658 1023
Summary of Change in VKT
Summary of ∆VKT (VKTt-VKTt-2)Year Interstates Trunk Highways CSAH
<0 =0 >0 <0 =0 >0 <0 =0 >01998 61 25 1107 403 298 1437 677 78 9031996 176 60 957 475 225 1438 554 127 9771994 198 61 934 587 303 1248 647 173 8381992 231 42 920 450 303 1385 888 160 6101990 181 52 960 562 135 1441 483 142 10331988 186 0 1007 561 75 1502 655 85 9181986 288 22 883 515 101 1522 379 82 11971984 79 8 1103 465 60 1613 464 30 11641982 330 4 859 736 46 1356 709 76 8731980 696 17 480 894 90 1154 769 77 812
Total 2426 291 9210 5648 1636 14096 6225 1030 9325
Model
€
Q = f (ΔQn
,ΔQpn
,ΔLn
,ΔLpn
,ΔPn ,ΔPan
,Qt,Qpt
,Lt,Lpt
,Pt,Pat
,D)
where :
t = base year
ΔQ = Change in VKT on the link between time t + n and t
ΔQn
= Change in VKT on the link between time t and t - n
ΔQpn
= Change in summed VKT on the parallel links between time t and t - n
ΔLn
= Change in the number of lanes on the link between time t and t - n
ΔLpn
= Change in the summed number of lanes on the parallel links between time t and t - n
ΔPn
= Change in the population of the MCD to which the link belongs, between time t and t - n
ΔPan
= Change in the summed population of the adjacent MCDs between time t and t - n
Qt
= VKT in the link at base year t
Qpt
= Summed VKT in the parallel links at base year t
Lt
= Number of lanes in the link at base year t
Lpt
= Summed number of lanes in the parallel links at base year t
Pt
= Population of the MCD to which the link belongs, at base year t
Pat
= Summed population of the adjacent MCDs, at base year t
D = Dummy variable for the base years
n = lag year = 2, 4, 6, 8
Dependent variable = Change in VKT between t+n and t(∆Q)
Variable [(t)-(t-n)] Hypothesis Summary Cases
Change in lanes on the link (∆Ln) + S +S 8/12
Number of lanes on the link in base year t (Lt) -S 6/12
Change in VKT on the link (∆Qn) + S -S 9/12
VKT on link in base year t (Qt) +S 8/12
Change in lanes on the parallel link (∆Lpn) - S +S 6/12
Number of lanes on the parallel link in base year t
(Lpt)
-S 9/12
Change in VKT on the parallel link (∆Qpn) -S 6/12
VKT on parallel links in base year t (Qpt) +S 8/12
Change in population of the MCD (∆Pn) + S +S 7/12
Population of the MCD at base year t (Pt) - S -S 7/12
Change in the summed population of the adjacent
MCDs (∆Pan)
+ S NS 7/12
Summed population of the adjacent MCDs at base
year t(Pat)
- S -S 11/12
Estimated Elasticities
Model Interstates Trunk Highways Hennepin County
Highways (CSAH)
2- year lag model Not Significant -.044 .045
4- year lag model -.143 .309 .148
6- year lag model .214 .195 .361
8- year lag model .565 Not Significant .422
ImplicationsIncrease in highway capacity has a small
but significant impact on individual’s activity and travel patterns
Expansion of Roadways does induced some additional demand, but the elasticity is < 1
New Construction has larger effectsEffect on Workers and Non-Workers are
different
Time Spent at Activities Increases
S1 S2
U
+ve
AS1 AS2
TS1
TS2
Time Spent
Traveling Decreases
Travel Time (T)
Activity Duration (A)
1440 minutes
1440 minutes
Utility Increases with Expansion
Fixed Daily Time Budget
“Demand” Line
Travel and Activity Duration Production Function
Data
• 1990/91 and 1995/96 Nationwide Personal Transportation Survey
• 1990 and 1995 Federal Highway Administration Highway Statistics
• Individuals whose total activities did not add to 1440 minutes (24 hrs), excluded
• This study looks only at adults, 18-65 years of age
• Excluded travelers with a daily shopping time greater than 420 minutes
Description of Variables
T90i Time spent at activity "i" in 1990
i Index of activities (travel to and duration at home, work, shop and other)
A Age
D Local population Density
G Gender
H Household Income levels
L Family lifecycle characteristics
M Month of year interview was conducted
S State specific variables
W Day of week interview was conducted
Methodology
• Since the NPTS was not conducted as a panel survey, we first estimate a model of 1990 individuals, and then apply that model to 1995 individuals in the form
T90i = f(A,D,G,H,L,M,S,W)• Estimated Travel Behavior for 1990 individuals can be determined in the form
^
T90i = f(A,D,G,H,L,M,S,W)95
• Then we estimated a difference model of change in travel behavior between the 1995 individuals their best estimate of 1990 behavior
Difference ModelDifference Model
C Difference in lane miles for all roadway types between 1995 and 1990
C90 Sum of lane miles for all roadway type in 1990
Δ F Difference in state average Fuel prices between 1995 and 1990
F90 State average Fuel price 1990
Δ I Difference in state average per capita Income between 1995 and 1990
I90 State level per capita Income in 1990
Δ P Difference in state Population between 1995 and 1990
P90 State Population in 1990
D95 Local population Density estimates in 1995
G95 Individual’s sex in 1995
L95 Family Lifecycle characteristics in 1995
Δ iT = 95iT −^
T90i change in time at activity "i" between 1995 and 1990 (estimated)
€
iT = f (ΔC /C90,ΔF /F90,ΔI /I90,ΔP /P90,D95,G95,L95)
s.t. Δ iTi=1
8
∑ =0
Hypothesis for Workers
TRAVEL TO TIME SPENT AT
H W S O
- - - -
TimeSavings
From Travel
FasterNetwork
TimeSavings
From Travel
H W SO
- -+ +
ReducedPeak
Spreading
Big BoxStores
PleasureOriented
TimeSavings
From Travel
Hypothesis for Non Workers
TRAVEL TO TIME SPENT AT
H S O
+ + -
More # of Home-Shop
Trips
FasterNetwork
H SO
++ -
LessDiscretionary
PleasureOriented
Elasticity of Time with respect to Elasticity of Time with respect to CapacityCapacity
* Indicates significance at 95% confidence level
Dependent variableChange in Minutes MinutesTravel time to
Home -3.17E-04 -1.08E-02 1.48E-02 * 5.28E-01Work -7.06E-03 * -1.23E-01 - -Shop -4.71E-02 * -1.90E-01 3.39E-02 * 2.35E-01Other -9.80E-03 * -1.60E-01 -2.91E-02 * -6.06E-01Time Spent atHome 7.27E-03 * 6.56E+00 2.19E-03 * 2.60E+00Work -1.80E-02 * -5.66E+00 - -Shop -3.44E-02 * -7.67E-01 2.54E-02 * 1.19E+00Other 2.72E-03 3.49E-01 -2.83E-02 * -3.95E+00
Non-workers Workers
%elasticities %elasticities
ResultsDue to Highway Capacity Expansion• Workers spend more Time at Home and
Other, Less Time at Work and Shop• Non-Workers spend more Time at Home
and Other, Less Time at Other• Non-workers take more Home to Shop
trips
Questions?