Sequential Demand Forecasting Models

1. Sequential Demand Forecasting Models CTC-340

2. Travel Behavior • 1. Decision to travel for a given purpose • People don’t travel without reason • 2. The choice of destination • 3. The choice of mode • 4. The choice of route or path

3. Trip generation • Forecast the number of trips which begin or end in a Traffic Analysis Zone • Must be calibrated • Dependent upon • land use • socioeconomic factors • at both ends

4. Trip Generation • Trip ends (Q) • How many trips are being made due to a land use • Production (P) • origin of residential based trip • Home - based trip -- begins or ends at home • non-home based trip -- trip does not begin or end at home • Attraction (A) • destination of residential based trip

5. Trip purpose • work, school, shopping, social, recreational • Can be single purpose or multi purpose

6. Zonal model • look at trips between zones • A zone is a homogeneous area of • land use • population • income • vehicle ownership • same access paths

7. Trip Rate Analysis • Determine the average productions and attractions of a trip generator • ITE Trip Generation Handbook • rates by land use • based on 1000 sf, employees, students, dwelling units, etc • Need to determine whether the generator or the adjacent street controls volumes generated • Why?

8. Pass-by trips • Trips not generated by land use • Vehicle deviates from its course to use land use and then continues on its path • What are major land uses where this type of trip is important • can be 25 - 60% of trips • Subtract trips from through traffic, add to turning traffic (in and out)

9. Linked Trips • Trips with multiple destinations all within one area and not requiring road access between destinations • 10 - 20 % of trips for certain land uses • Used in Malls and shopping centers

10. Example • Drive in Bank 5,000 sf w/drive thru • 60,000 sf office building • AM & PM trips • What other times might be important?

11. 131 Single Family Homes 370 Townhouse units 400 Garden Apartments 640K Office Park 257K Shopping center 3 banks & Restaurants 365K Industrial Park 90K Medical Office 180 Room Hotel Grand Vista

12. Grand Vista • Spreadsheet

13. Trip Distribution • Where do the trips come from? • Gravity Model provides answers • force of attraction between two bodies is proportional to the product of their masses and inversely proportional to the product of the distance between them

14. Trip Distribution • F is the friction factor • proportional to W • F = 1/W^2 • P is productions in i • A is attractions in j • Q is the trips from i to j • K is the difference in socio-economic factors from i to j

15. Trip Distribution • Gravity model works for large and small developments • may need to calibrate large developments • usually use census tracts as zones • can use information developed by developer • Retail stores use zip codes

16. Trip Distribution • Attraction depends on • uniqueness • distance • closeness to other services • urban or rural • Shopping Centers usually have a 5 mile radius of influence

17. Grand Vista • 6 access roads • Need to distribute traffic to each site driveway • Based on destination/start point • This is where judgment comes in • Spreadsheet

18. Modal Choice • Trip makers choose mode • trip type is a factor • socio-economic status is a factor • transit captives • 2 types of models • pre-distribution - attraction has no impact on mode • Post-distribution – attraction does impact mode

19. Models • Diversion curves • based on auto costs, transit travel time, auto travel time, transit LOS, auto LOS, income

20. Models • Utility and Disutility • measures satisfaction or impedance of choice • All provide a percentage of trips per mode • As inputs change, outputs also change

21. Network Assignment • Determine path • Number of paths depends on network • person trips vs vehicle trips • Transit Assignment • depends on capacity, facilities, connectivity

22. Network Assignment • 3 major times - Peak Hours • Trip direction is important • Diversion Curves • good when only two paths to choose from • arterial vs freeway • many iterations • based on travel time of each facility

23. Link Flow • Flow that occurs on a link in a network • Route Choice Behavior • user equilibrium • goes on shortest path • system equilibrium • cost of system is minimized • stochastic equilibrium • user assigns self to “shortest path”

24. Minimum Path Algorithms • Minimizes most important user criteria • cost, time, distance • can also develop trade-offs between criteria to determine “best route” • can determine the traffic on a link

25. Minimum Path Algorithms • All or Nothing • Multipath Traffic Assignment • Capacity Restrained • Transit Assignment

26. All or Nothing • Need to find minimum path tree for network • place traffic on links • gives info on most heavily used links • not accurate for high volumes

27. Grand Vista • Add traffic to links to get build volumes • Spreadsheet

28. All or Nothing Example

29. Volumes

31. Volumes