Road Capacity and Allocation of TimeRoad Capacity and Allocation of Time
David M LevinsonUniversity of Minnesota
Seshasai KanchiICF Consulting
81st Transportation Research Board Meeting
16th January 2002Levinson, David and Seshasai Kanchi (2002) Road Capacity and Allocation of Time, Journal of Transportation and Statistics 5(1) pp 25-46.http://nexus.umn.edu/Papers/RoadCapacity.pdf
OutlineOutline
Introduction Data Travel Time and Activity Duration Analysis Theory of Daily Time Budgets Methodology Results Conclusions
IntroductionIntroduction
Travel and Activity are Two Sides of the Same Coin
Time in Travel = f (Time at Activity, # Trips) Primary Activities Considered: Home, Work,
Shop and Other Daily Activity Budget (24 hrs)
DataData
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
Activity Duration CalculationActivity Duration Calculation
PERSON ID ORIGIN DEST TT START TIME END TIME* TIME SPENT*1 H O 15 8:30 8:45 301 O W 15 9:15 9:30 3601 W O 15 15:30 15:45 1051 O O 10 17:30 17:40 201 O H 10 18:00 18:20 8502 H W 20 8:00 8:20 3402 W O 15 14:00 14:15
Travel time and Activity durationTravel time and Activity durationComparison of 1990 and 1995 NPTSComparison of 1990 and 1995 NPTS
* Denotes Significance at 95% level
SEX_YEAR WORK STATUS TRAVEL CASESHOME WORK SHOP OTHER
Female1995 Non Worker 1172* 0 42* 166* 60 28121990 1220 0 35 127 58 10201995 Worker 944 313* 25* 93* 65 80141990 928 284 30 132 65 2535Male1995 Non Worker 1171* 0 30 177* 62 12401990 1222 0 29 130 59 3611995 Worker 900 365* 15* 90* 70 77161990 903 338 20 110 69 2275
TIME SPENT AT
Comparison of Travel and Activity Comparison of Travel and Activity Patterns of 1990 and 1995 NPTSPatterns of 1990 and 1995 NPTS
Time Spent at Home Decreased for Non Workers and Female Workers
Time at Home in 1990 Substituted for Work in 1995, especially for Female Workers
Time Spent at Other Declined for Workers but Increased for Non-Workers
Overall Travel Times have either remained Stable or Increased, but not significant
Induced TravelInduced Travel
S1: Supply before
S2: Supply after
Price of Travel
Quantity of Travel (VMT)
Q1 Q2
P1
P2
Demand
How does Highway Expansion affect How does Highway Expansion affect Travel and Activity PatternsTravel and Activity Patterns
Makes network becomes faster, higher attainable speeds lead to time savings in travel
Increases accessibilityBroadens commuter’s travel choicesMore non-travel activitiesIndividuals maximize their utility
Time Spent at Activities Decreases
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 FunctionTravel and Activity Duration Production Function
Model EstimationModel Estimation
Seemingly Unrelated Regression Estimation (SURE) is used
They use asymptotically efficient, feasible generalized least squares estimation
It overrules the assumption of OLS that error residuals are not interrelated
Description of VariablesDescription 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
MethodologyMethodology
• 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
ΔΧ
Difference in lane miles for all roadway types between 1995 and 1990
C90 Sum of lane miles for all roadway type in 1990
Δ
Φ Δ ι φ φ ε ρ ε ν χ ε ι ν σ τ α τ ε α ϖ ε ρ α γ ε Φ υ ε λ π ρ ι χ ε σ β ε τ ω ε ε ν 1 9 9 5 α ν δ 1 9 9 0
F90 State average Fuel price 1990
Δ
Ι Δ ι φ φ ε ρ ε ν χ ε ι ν σ τ α τ ε α ϖ ε ρ α γ ε π ε ρ χ α π ι τ α Ι ν χ ο μ ε β ε τ ω ε ε ν 1 9 9 5 α ν δ 1 9 9 0
I90 State level per capita Income in 1990
Δ
Π Δ ι φ φ ε ρ ε ν χ ε ι ν σ τ α τ ε Π ο π υ λ α τ ι ο ν β ε τ ω ε ε ν 1 9 9 5 α ν δ 1 9 9 0
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)
Δ iT = f(ΔC /C90,ΔF /F90,ΔI / I90,ΔP /P90,D95,G95,L95)
s.t. Δ iTi=1
8
∑ =0
Difference ModelDifference Model
Hypothesis for WorkersHypothesis 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 WorkersHypothesis 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 CapacityElasticity of Time with respect to Capacity
* 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
ResultsResults
Due 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
ConclusionsConclusions
Overall Travel Times have remained stable while Activity Durations changed significantly
Increase in highway capacity has a small but significant impact on individual’s activity and travel patterns
Effect on Workers and Non-Workers are different
Questions?
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