NCHRP Report 765 Overview. Rob Bostrom August 15, 2014 ARC Model Users Group

Transcription

1 NCHRP Report 765 Overview Rob Bostrom August 15, 2014 ARC Model Users Group

2 Presentation Overview NCHRP Report 765 Overview Focus on ARC Case Study Spreadsheets Sketch Planning Techniques

3 NCHRP REPORT OVERVIEW

4 NCHRP Report 765 NCHRP 8 83 (NCHRP Report 765) Started in March, 2011 Finished in October, 2013 Published in July, p_rpt_765.pdf Need Guidance to produce traffic forecasts for design, planning and operational project analysis Models and other tools produce results that need smoothing or factoring Updates NCHRP 255 which has been used since 1982 refining traffic forecasts

5 Project Background Program Manager: Nanda Srinivasan Team CDM Smith: Rob Bostrom, Principal Investigator, several others Alan Horowitz of University of Wisconsin at Milwaukee, since retired Tom Creasey of Stantec Ram Pendyala of Arizona State University, now at Emory Mei Chen of University of Kentucky Panel Chair: Mike Bruff of NC DOT Sarah Sun, Kermit Wies, Eric Pihl, Robert Winnick, Doug Laird, Jeff Shelton, Subrat Mahapatra, Derek Miura, Matthew Hardy, Phillip Cox, Dan Lamers

6 Contents Background Introduction Overview of the Fundamentals of Traffic Forecasting Overview of Traffic Forecasting Tools and Methodologies Guidelines The Project Level Traffic Forecasting Process Working with a Travel Model Model Output Refinements Refining the Spatial Data of Traffic Models Improving the Temporal Accuracy of Traffic Forecasts Traffic Forecasting Methods for Special Purpose Applications Tools Other than Travel Models Case Studies

7 Final Draft Report: Chapter 1 Introduction What are projects? History/context/significance of NCHRP 255 Chapter by chapter review of NCHRP 255 Forecasting state of the practice: national survey and source documents Organization of report

8 Chapter 2: Overview of the Fundamentals of Traffic Forecasting Traffic forecasting parameters and source data e.g. ADT, DHV, T% Traffic forecasting tools TDMs and more Measures of effectiveness see graphic Essential bookshelf must reads for forecasters

9 Chapter 3: Overview of Traffic Forecasting Tools and Methodologies The travel forecasting model ideal State of the practice travel forecasting models SOP of data inputs for travel forecasting models SOP of outputs for travel forecasting models Defaults vs. locally specific parameters Other traffic forecasting tools and methodologies

10 Chapter 4: The Project Level Forecasting Process Traffic forecasting context Application Scope Traffic forecasting steps Preparation Forecast development QA/QC Documentation

11 Chapter 4: The Project Level Forecasting Process Key Traffic Forecasting Considerations Accuracy Judgment Traffic forecasting rules of thumb: precision/rounding, importance of data

12 Chapter 5: Working with a Travel Model Understanding your model Validation methods and standards Errors and variability in speed and volume data Fixing issues in input or validation data Understanding travel model outputs Dealing with outliers in model outputs

13 Chapter 5: Working with a Travel Model Default free flow travel times for a TDM:

14 Chapter 6: Model Output Refinements Screenline refinement and base volumes Refining turning movement outputs of travel models Refining directional splits from travel models Refining speed and travel time outputs of travel models Model refinement with origin destination matrix estimation

15 Chapter 7: Refining the Spatial Detail of Traffic Models Focusing: enhancing detail in regional or statewide models Windowing (subarea model) Custom subarea focused models Multi resolution modeling systems Hybrid models Refining E E trip tables Case studies

16 Chapter 8: Improving The Temporal Accuracy of Traffic Forecasts Activity and tour based model systems Dynamic traffic assignment Peak spreading Pre assignment factoring Post assignment factoring Day of week Month of year Vehicle class considerations Case studies

17 Chapter 8: Pre assignment table (NCHRP 716)

18 Chapter 8: Post assignment table Hourly factors derived from ATRs for post assignment ADT processing. Categories: urban area small/medium/large, rural area; ½ of table below

19 Chapter 9: Traffic Forecasting Methods for Special Purpose Applications Basic forecasts w/ ADT, DHV and turning movements Data extrapolations Vehicle mix & MOVES ESALs Benefit cost analysis Toll/revenue forecasts Work zone congestion Incident management Non recurring congestion Environmental justice Traffic impact studies

20 Chapter 10: Tools Other than Travel Models When to use non TDM methods Time series of traffic volume data Sketch planning and spreadsheet techniques Elasticity methods Post processing using HCM 2010 Stitching a model together

21 Chapter 11: Case Studies Suburban Arterial network Network window Small city (Charleston, SC) Large City (Atlanta) Time series on a link Blending a TDM and microsimulation

22 Appendices Glossary/acronyms Survey/expert panel/nchrp 255 detailed review Modeling source documents Examples Traffic forecasting Trend line analysis Turning movement Model spreadsheet Modeling checklist

23 NCHRP 765 Recommendations Project level forecasting, for the most part, use travel models and/or time series. Sketch planning tools are also fine for traffic forecasting. Most traffic forecasts for projects need some sort of refinement. Ratios/deltas ODME Engineering judgment is allowed and encouraged must be documented though!

24 ARC CASE STUDY

25 Using an ABM for Project Traffic Forecasting ARC Model w/ TOD and static assignment Scenario: conversion of HOV lane to HOT lane

26 Running the Model Population change from population generator

27 Managed Lane Results

28 Peak Toll Trips

29 Change in Trip Model Share

30 SPREADSHEET TOOLS

31 Spreadsheet Tools Found in CD attached to report Tools documented Corridor matrix estimation Intersection OD estimation NCHRP 255 Turns Traffic Volume Refinement Tools undocumented (North Carolina Tool) ADT growth calculator STDDev calculator Intersection current/future year Interpolation Many more!

32 Example: Traffic Volume Refinement Documentation in Chapter 6 Concept is to factor future model volumes by a relationship between the current year traffic counts and the base year model volumes. See Spreadsheet

33 SKETCH PLANNING TECHNIQUES

34 Sketch Planning Techniques Manual Gravity originally developed by KYTC, seehttp://transportation.ky.gov/planning/documents/manual%20gravity%20d iversion%20report.pdf Subarea focusing Windowing Time Series Elasticity Methods HCM Methods

35 Manual Gravity Purpose: Determine traffic diversion in areas lacking travel demand model Data Needs Traffic control data (posted speed, signal information, segment lengths, etc.) Physical characteristics (number of lanes, lane widths, turn bays, directional factors, etc.) Traffic characteristics (growth rate, K factor, peak hour factor, truck percentage, etc.) Base year no build ADT traffic volumes Future year no build ADT traffic volumes ADT turning movements at major intersections It is a gravity diversion in that trips are diverted to the new route based on its attractiveness, expressed as a distance and travel time advantage over the existing route.

36 Manual Gravity There are five steps involved in performing a manual gravity diversion to determine the traffic volume diverted to a new facility. Estimate free flow speed Calculate roadway capacity Generate the no build traffic forecasts Estimate congested travel speed Apply California DOT diversion curves

37 Manual Gravity Apply California DOT Deviation Curves Determine the volume of traffic moving between a given OD pair Determine the distance between the OD pair using the existing route and the best available route using the new facility Determine the congested travel times between the OD pair Calculate the percentage of diverted traffic using the CA DOT deviation equation P = * (Δd+ 0.5 * Δt) / SQRT [ ( Δd 0.5 * Δt) ] Multiply the OD volume by P and assign this volume to the bypass, assign the balance to the existing route Repeat for every OD pair that may use the new bypass facility For the design year analysis, increase the volume assigned to the new facility by 20% to account for induced traffic.

38 Example

39 Example

40 CONCLUSION

41 NCHRP 765: What s Next? Forecast guidelines for areas not covered such as transit forecasting More work on hot areas Speed data usage for forecasting Forecasting accuracy/ranges Refinement of toolkit approach NCHRP 8 84 ongoing Development of forecast adjustments for metrics other than volumes. Nanda mentioned a possible update in five years. Consideration of a TRB forecasting committee not just modeling!

42 Thanks for your attention! Any questions/comments Rob Bostrom, Alan Horowitz, Tom Creasey,