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

TRB Planning Applications ConfereTRB Planning Applications Conferencence

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

RegionRegion

Jim D. Benson, Texas Transportation InstituteJim D. Benson, Texas Transportation InstituteChris Van Slyke, Houston-Galveston Area Chris Van Slyke, Houston-Galveston Area

CouncilCouncilAlan C. Clark, Houston-Galveston Area CouncilAlan C. Clark, Houston-Galveston Area Council


Today’s PresentationToday’s Presentation

Dimensioning The ProblemDimensioning The Problem Study Area And Data BaseStudy Area And Data Base Trip Generation ModelsTrip Generation Models Trip Distribution ModelsTrip Distribution Models Time-of-day FactorsTime-of-day Factors Developing Alternative ScenariosDeveloping Alternative Scenarios


Hurricane Rita – Sept 2005Hurricane Rita – Sept 2005


Evacuation ZonesEvacuation Zones



Example Evacuation SpeedsExample Evacuation Speeds US 290 WB FM 1960 to Barker Cypress

0

10

20

30

40

50

60

70

80

0 4 8 12 16 20 24 28 32 36 40 44 48

Hourly Time Periods (9/21 - 9/22/05)

Sp

eed

Morning 9/22


H-GAC Study AreaH-GAC Study Area


Houston TranStar Rita Houston TranStar Rita Evacuation SurveyEvacuation Survey

Solicited participation on websiteSolicited participation on website Participants responded to questions Participants responded to questions

onlineonline 6,570 respondents6,570 respondents 6,286 usable household responses6,286 usable household responses 3,886 households evacuated by car 3,886 households evacuated by car

or truckor truck


Evacuation Generation Evacuation Generation ModelsModels

Models developed for Rita eventModels developed for Rita event

Structured to facilitate exploring Structured to facilitate exploring different evacuation scenarios different evacuation scenarios


APPROACHAPPROACH

Six-day event modeledSix-day event modeled Cross-classification variables:Cross-classification variables:

– 6 geographical districts6 geographical districts– 5 household size groups5 household size groups

Production models:Production models:– Probability of evacuatingProbability of evacuating– Vehicle trips/evacuation householdVehicle trips/evacuation household– Trip purpose splitTrip purpose split

Simple attraction modelsSimple attraction models Non-resident trip modelsNon-resident trip models


Six DistrictsSix Districts


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Dist 1 Dist 2 Dist 3 Dist 4 Dist 5 Dist 6

Percent of Households Evacuating



1 pph

3 pph

5+ pph

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

Vehicle Trips/Evacuated Household

1 pph

2 pph

3 pph

4 pph

5+ pph


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


Percent of Internal Trips Exiting


Internal Evacuation Internal Evacuation AttractionsAttractions

HouseholdsHouseholds 83.3%83.3%

Hotels & MotelsHotels & Motels 8.4%8.4%

Public ShelterPublic Shelter 2.0%2.0%

OtherOther 6.3%6.3%


External Station Evacuation External Station Evacuation AttractionsAttractions

Distributed attractions to other urban Distributed attractions to other urban areas based on their population and areas based on their population and relative accessibilityrelative accessibility

Allocated results to external stationsAllocated results to external stations


Rita Evacuation Generation Rita Evacuation Generation ResultsResults

Internal-InternalInternal-Internal

(residents)(residents)218,785218,785

Internal-ExternalInternal-External

(residents)(residents)1,040,9361,040,936

External-InternalExternal-Internal

(non-residents)(non-residents)5,4065,406

External-ExternalExternal-External

(non-residents)(non-residents)21,61721,617


0

50000

100000

150000

200000

250000

300000

350000

400000

Trips

1 2 3 4 5 6

District

Resident Vehicle Evacuation Trips By District


Split of Resident Evacuation Trips

Districts 1-3 - 38%

Districts 4-6 - 62%


Two Trip Distribution ModelsTwo Trip Distribution Models

Evacuation trips to internal zonesEvacuation trips to internal zones

Evacuation trips to external stationsEvacuation trips to external stations


Distribution Model For Internal Distribution Model For Internal AttractionsAttractions

Essentially a “constrained interactance” Essentially a “constrained interactance” modelmodel

No friction factorsNo friction factors No iterative processNo iterative process Constrained to productionsConstrained to productions Interaction constraint Interaction constraint Productions allocated to eligible Productions allocated to eligible

attraction zones based on relative attraction zones based on relative attractiveness attractiveness


Interaction ConstraintInteraction Constraint

No attractions to zones in the 3 No attractions to zones in the 3 mandatory evacuation areas mandatory evacuation areas

Eligible attraction zones must be Eligible attraction zones must be either:either:– Further from the coast, ORFurther from the coast, OR– 80+ miles from the coast80+ miles from the coast


Distribution Model For External Distribution Model For External Station AttractionsStation Attractions

Similar to traditional external-local Similar to traditional external-local modelsmodels

Primary difference: external stations Primary difference: external stations are treated the attractionsare treated the attractions

Somewhat relaxed version of the Somewhat relaxed version of the normal external-local friction factors normal external-local friction factors usedused


TRIP DISTRIBUTION RESULTSTRIP DISTRIBUTION RESULTS

EvacuationEvacuation

Trip Trip PurposesPurposes

EvacuationEvacuation

TripsTrips

AverageAverage

TripTrip

LengthLength

(miles)(miles)

MaxMax

TripTrip

LengthLength

(miles)(miles)

Trips toTrips to

InternalInternal

ZonesZones224,189224,189 36.936.9 139139

Trips toTrips to

ExternalExternal

StationsStations1,062,7571,062,757 62.362.3 156156


Time-of-day FactorsTime-of-day Factors

Estimated from survey dataEstimated from survey data

Developed for each of the six Developed for each of the six districtsdistricts

Hourly Distribution for 6-day EventHourly Distribution for 6-day Event


% Distribution of Trips by Day

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7

Day of 6-day Event

%

Dist 1

Dist 2

Dist 3

Dist 4

Dist 5

Dist 6


Distribution of Evacuation Trips by HourFrom Survey

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80

Hour of 72-hour period (days 3-5)

% o

f E

ven

t T

rip

s Dist 1

Dist 2

Dist 3

Dist 4

Dist 5

Dist 6


Developing Alternative Developing Alternative ScenariosScenarios

Consider adjustments to % households Consider adjustments to % households evacuating by districtevacuating by district

Consider adjusting hourly distributions Consider adjusting hourly distributions by districtby district

Consider adjusting vehicle trip rates to Consider adjusting vehicle trip rates to reflect taking fewer vehicles by districtreflect taking fewer vehicles by district


Questions?Questions?

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

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