Incorporating Feedback in Travel Forecasting: Methods, Pitfalls and Common Concerns : Final Report
U.S. Department of Transportation, 1996 - Traffic assignment
The most common method for producing regional or metropolitan area travel forecasts in the United States is to apply the following four modeling steps sequentially: trip generation; trip distribution; mode choice; and, route assignment. This traditional 4-step process passes output from one step to the next as input. While the process has produced forecast results sufficiently accurate for many types of long range transportation planning, it is commonly found that some of the outputs of the process are not consistent with inputs to earlier steps. The research undertaken in this project focused on methods to ensure that link speeds used in each step of the travel forecasting process are consistent with the final speeds estimated in the final step of the process. As a product of this research, a final report was prepared to provide guidance in the application of feedback.
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WHEN AND WHERE SHOULD FEEDBACK BE APPLIED 2 1
IMPLEMENTATION OF FEEDBACK 3 1
THE EFFECTS OF FEEDBACK 4 1
All-or-Nothing Assignment altemative Alternative Feedback Methods average speed baseline Boyce Clean Air Act composite impedances congestion levels convergence characteristics convergence criteria Direct Feedback Direct Method Effects of Feedback equilibrium assignment execution Federal Highway Administration Feedback Framework feedback mechanisms feedback process ﬁnal ﬁrst four-step process implementation of feedback implementing feedback increase input integrated mode choice introducing feedback introduction of feedback iteration's Lake City model Memphis and Salt Memphis metropolitan area Method of Optimal Method of Successive model system modeling process models with feedback MSA Equilibrium MSA-AON MSA-EQA non-attainment number of iterations Optimal Weighting options overall solution person trips previous iterations produce provides recalibration reﬂect regional Root Mean Square round-off error Salt Lake City sensitivity sensitivity tests signiﬁcant signiﬁcantly speciﬁc step Successive Averages system-wide test-case models traditional four-step trafﬁc transportation transportation forecasting travel characteristics travel forecasting process trip distribution trip tables U.S. EPA updated V/C ratio zones