Southern California Ozone StudyMOBILE SOURCE IMPROVEMENTS

Ed YotterPlanning & Technical Support Division

California Air Resources BoardSacramento, CA

Southern California Ozone StudyTRAVEL DEMAND MODELING

Travel Demand Modeling (TDM) What is a TDM? Previous SCAG TDM Current SCAG TDM Heavy Duty Truck TDM

Direct Travel Impact Model (DTIM4)Day Specific Mobile Source ActivityEMFAC2000

Southern California Ozone StudyTRAVEL DEMAND MODELING

What is a TDM? Estimates Personal Travel Generation

Socio-Economic DataHome Interview Travel Diaries

Person Trip Distribution Mode Choice (Walk, auto, bus, etc) Auto Assignment

Network Link VolumesTrip-end Activity

Southern California Ozone StudyTRAVEL DEMAND MODELING - Generation

Southern California Association of Governments (SCAG) Modeling Study Area Traffic Analysis Zone System Socio-Economic Data

PopulationHousing / IncomeEmployment

Network

Southern California Ozone StudyTRAVEL DEMAND MODELING - STUDY AREA

Southern California Ozone StudyTRAVEL DEMAND MODELING - TAZs

Southern California Ozone StudyTRAVEL DEMAND MODELING - NETWORK

Southern California Ozone StudyTRAVEL DEMAND MODELING - Socio-Economic Data { Population }

Southern California Ozone StudyTRAVEL DEMAND MODELING - Socio-Economic Data { Household Income }

Southern California Ozone StudyTRAVEL DEMAND MODELING - Socio-Economic Data { Employment }

Southern California Ozone StudyTRAVEL DEMAND MODELING - Distribution

DISTRIBUTION Productions & Attractions

Peak PeriodsOff-Peak PeriodsBy Trip Purpose

Trip Purpose (Home-based, Non-home based)Examples:

• Home-based Work• Home-based Shop• Home-based School• Work to Other• etc

Southern California Ozone StudyTRAVEL DEMAND MODELING - Mode Choice

MODE CHOICE Non-Motorized (Walk / Bicycle) Automobile

DriverPassenger

TransitBusRail

Southern California Ozone StudyTRAVEL DEMAND MODELING - Assignment

ASSIGNMENT Feedback Loops

Realistic Travel Times and CostsMode Choice (auto, bus, rail, etc)

Validation of ResultsVolumesTime of DayTravel Time

Screenline Validation

Southern California Ozone StudyTRAVEL DEMAND MODELING - SCREENLINES

Southern California Ozone StudyHEAVY DUTY TRUCK MODEL

GENERATION S/E Data

Commodity Flow Database (STCC)• Inbound Flows• Outbound Flows

Special Generators (Airports & Seaports)

HDT ClassesLight-heavy (8,500 to 14,000 GVW)Medium-heavy (14,000 to 33,000 GVW)Heavy-heavy (over 33,000 GVW)

Southern California Ozone StudyHEAVY DUTY TRUCK MODEL

GENERATION (continued)Outbound truckloadPrivate truck modeLess-than-truckload

• By STCC• By HDT vehicle class

Time of day

Southern California Ozone StudyHEAVY DUTY TRUCK MODEL

DISTRIBUTION Truck Trip

External Truck Trips (X-I & I-X)Internal Truck Trips (I-I)Through Truck Trips (X-X)

Time PeriodMorning Peak (6am - 9am)Mid-day (9am - 3pm)Evening Peak (3pm - 7pm)Night (7pm - 6am)

Southern California Ozone StudyHEAVY DUTY TRUCK MODEL

ASSIGNMENT Special Considerations

Truck Prohibitions (e.g. Pasadena Freeway)Significant Grades

Passenger Car Equivalents (PCE)Example: 5-10% Trucks, 3% Grade, Length > 1

mile• Light-heavy duty truck = 4.2 passenger cars• Medium-heavy duty truck = 5.9 passenger cars• Heavy-heavy duty truck = 7.8 passenger cars

Congestion Adjustments (as much as 34% increase)

Southern California Ozone StudyCOMBINED TRAVEL DEMAND MODELS

COMBINED MODEL ASSIGNMENT Auto Assignment Heavy-duty Truck Assignment

with PCE & Congestion Adjustments

Final Network LoadingRealistic Speeds on LinksImproved Volume EstimatesScreenline Validation

Southern California Ozone StudyDIRECT TRAVEL IMPACT MODEL (DTIM)

TRAVEL DEMAND MODELLINK VOLUMES & SPEEDSTRIP-END DATANETWORK DESCRIPTION BY TIME PERIOD

EMFAC2000CALENDAR YEAR & SEASONCOMPOSITE EMISSION RATES BY VEHICLE CLASS BY TEMPERATURE & RELATIVE HUMIDITY, BY SPEED

USER PROGRAM CONTROLS

GRIDDED AREANETWORK TO GRID TRANSFORMATIONSTARTS/PARKS/STABLES FACTORS FROM PERIOD TO HOUR

METEOROLOGYGRIDDED DAY SPECIFIC TEMPERATURES & RELATIVE HUMIDITY DIRECT TRAVEL

IMPACT MODEL

GRIDDED MOTOR VEHICLE EMISSIONSHOUR OF THE DAYPOLLUTANTPROCESS

Southern California Ozone StudyDTIM - GRIDDED EMISSIONS