Post on 31-Dec-2015
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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 - 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 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