TRB Planning Applications Conference Development of Hurricane Rita Evacuation Trip Tables for the Houston-Galveston Region Jim D. Benson, Texas Transportation Institute Chris Van Slyke, Houston-Galveston Area Council Alan C. Clark, Houston-Galveston Area Council

TRB Planning Applications Conference Today’s Presentation Dimensioning The Problem Dimensioning The Problem Study Area And Data Base Study Area And Data Base Trip Generation Models Trip Generation Models Trip Distribution Models Trip Distribution Models Time-of-day Factors Time-of-day Factors Developing Alternative Scenarios Developing Alternative Scenarios

TRB Planning Applications Conference Hurricane Rita – Sept 2005

TRB Planning Applications Conference Evacuation Zones

TRB Planning Applications Conference

Example Evacuation Speeds Morning 9/22

TRB Planning Applications Conference H-GAC Study Area

TRB Planning Applications Conference Houston TranStar Rita Evacuation Survey Solicited participation on website Solicited participation on website Participants responded to questions online Participants responded to questions online 6,570 respondents 6,570 respondents 6,286 usable household responses 6,286 usable household responses 3,886 households evacuated by car or truck 3,886 households evacuated by car or truck

TRB Planning Applications Conference Evacuation Generation Models Models developed for Rita event Models developed for Rita event Structured to facilitate exploring different evacuation scenarios Structured to facilitate exploring different evacuation scenarios

TRB Planning Applications Conference APPROACH Six-day event modeled Six-day event modeled Cross-classification variables: Cross-classification variables: –6 geographical districts –5 household size groups Production models: Production models: –Probability of evacuating –Vehicle trips/evacuation household –Trip purpose split Simple attraction models Simple attraction models Non-resident trip models Non-resident trip models

TRB Planning Applications Conference Six Districts

TRB Planning Applications Conference

Internal Evacuation Attractions Households83.3% Hotels & Motels 8.4% Public Shelter 2.0% Other6.3%

TRB Planning Applications Conference External Station Evacuation Attractions Distributed attractions to other urban areas based on their population and relative accessibility Distributed attractions to other urban areas based on their population and relative accessibility Allocated results to external stations Allocated results to external stations

TRB Planning Applications Conference Rita Evacuation Generation Results Internal-Internal (residents) (residents)218,785 Internal-External 1,040,936 External-Internal (non-residents) (non-residents)5,406 External-External 21,617

TRB Planning Applications Conference

Two Trip Distribution Models Evacuation trips to internal zones Evacuation trips to internal zones Evacuation trips to external stations Evacuation trips to external stations

TRB Planning Applications Conference Distribution Model For Internal Attractions Essentially a “constrained interactance” model Essentially a “constrained interactance” model No friction factors No friction factors No iterative process No iterative process Constrained to productions Constrained to productions Interaction constraint Interaction constraint Productions allocated to eligible attraction zones based on relative attractiveness Productions allocated to eligible attraction zones based on relative attractiveness

TRB Planning Applications Conference Interaction Constraint No attractions to zones in the 3 mandatory evacuation areas No attractions to zones in the 3 mandatory evacuation areas Eligible attraction zones must be either: Eligible attraction zones must be either: –Further from the coast, OR –80+ miles from the coast

TRB Planning Applications Conference Distribution Model For External Station Attractions Similar to traditional external-local models Similar to traditional external-local models Primary difference: external stations are treated the attractions Primary difference: external stations are treated the attractions Somewhat relaxed version of the normal external-local friction factors used Somewhat relaxed version of the normal external-local friction factors used

TRB Planning Applications Conference TRIP DISTRIBUTION RESULTS Evacuation Trip Purposes EvacuationTripsAverageTripLength(miles)MaxTripLength(miles) Trips to InternalZones224, ExternalStations1,062,

TRB Planning Applications Conference Time-of-day Factors Estimated from survey data Estimated from survey data Developed for each of the six districts Developed for each of the six districts Hourly Distribution for 6-day Event Hourly Distribution for 6-day Event

TRB Planning Applications Conference

Developing Alternative Scenarios Consider adjustments to % households evacuating by district Consider adjustments to % households evacuating by district Consider adjusting hourly distributions by district Consider adjusting hourly distributions by district Consider adjusting vehicle trip rates to reflect taking fewer vehicles by district Consider adjusting vehicle trip rates to reflect taking fewer vehicles by district

TRB Planning Applications Conference Questions?