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Development of Hurricane Rita Evacuation Trip Tables for the Houston-Galveston Region : 

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

Today’s Presentation : 

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

Hurricane Rita – Sept 2005 : 

TRB Planning Applications Conference Hurricane Rita – Sept 2005

Evacuation Zones : 

TRB Planning Applications Conference Evacuation Zones

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TRB Planning Applications Conference

Example Evacuation Speeds : 

TRB Planning Applications Conference Example Evacuation Speeds Morning 9/22

H-GAC Study Area : 

TRB Planning Applications Conference H-GAC Study Area

Houston TranStar Rita Evacuation Survey : 

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

Evacuation Generation Models : 

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

APPROACH : 

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

Six Districts : 

TRB Planning Applications Conference Six Districts

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TRB Planning Applications Conference

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TRB Planning Applications Conference

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TRB Planning Applications Conference

Internal Evacuation Attractions : 

TRB Planning Applications Conference Internal Evacuation Attractions

External Station Evacuation Attractions : 

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

Rita Evacuation Generation Results : 

TRB Planning Applications Conference Rita Evacuation Generation Results

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TRB Planning Applications Conference

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TRB Planning Applications Conference

Two Trip Distribution Models : 

TRB Planning Applications Conference Two Trip Distribution Models Evacuation trips to internal zones Evacuation trips to external stations

Distribution Model For Internal Attractions : 

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

Interaction Constraint : 

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

Distribution Model For External Station Attractions : 

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

TRIP DISTRIBUTION RESULTS : 

TRB Planning Applications Conference TRIP DISTRIBUTION RESULTS

Time-of-day Factors : 

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

Slide 26: 

TRB Planning Applications Conference

Slide 27: 

TRB Planning Applications Conference

Developing Alternative Scenarios : 

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

Questions? : 

TRB Planning Applications Conference Questions?