Presentation on theme: "Traffic Forecasting on Trunk Highways in Nonmetropolitan Areas: A Survey of State Practice Presentation to MnDOT Technical Advisory Panel Wednesday, September."— Presentation transcript:
Traffic Forecasting on Trunk Highways in Nonmetropolitan Areas: A Survey of State Practice Presentation to MnDOT Technical Advisory Panel Wednesday, September 26, :00 p.m. Christine Kline Patrick C. Casey CTC & Associates LLC Madison, Wisconsin Transportation Research Synthesis:
Background Traffic forecasting plays a critical role for MnDOT in corridor planning, geometric design, pavement design, safety analysis, access management and more. In previous decades, Minnesota has seen steady growth in vehicle miles traveled. In recent years, VMT growth in Minnesota has been flat and declined by 0.5% from 2009 to 2010.
TRS project scope MnDOTs Office of Transportation Data & Analysis wanted to know: How other states are dealing with what appears to be a nationwide trend in a leveling off or decline in VMT. The forecasting methods used by other state DOTs to project traffic volumes in nonmetropolitan areas with a population under 50,000.
Technical Advisory Panel Shirlee Sherkow, Project Coordinator Chu Wei, Technical Liaison Technical Advisory Panel Members Lynne BlyJim Miles Gene HicksTom Nelson Jason JungePaul Stine James McCarthy
Methodology We distributed an online SurveyMonkey survey to members of the AASHTO Standing Committee on Planning.an online SurveyMonkey survey Nine-question survey, reviewed and approved by the TAP, of open-ended and multiple-choice questions July 30 announced the survey, with two weeks for responses (August 10 survey deadline) August 7 reminder encouraged more responses September 7 final draft of report sent to TAP
Methodology The survey gathered information in four key areas: Methodologies and tools used to estimate future traffic volumes Data and factors used in forecasting Projection time periods Flattening or decrease in VMT
Survey response Rhode Island provided an response All planning is performed by the states metropolitan planning organization; Rhode Island DOT has no forecasting procedures for nonmetropolitan areas Not all respondents answered every question Percentages noted in survey results are adjusted accordingly
Survey results Question 1: Please indicate the methodology(ies) used in your agencys program to estimate future traffic volumes. Regression ModelsState Box-Cox linear regressionWI Cubic regressionNM Least squares regressionAZ, KS, NM, PA Linear regressionAZ, CT, FL, IA, IL, KS, KY, MA, ME, MI, MN, MO, MS, MT, NC, ND, NE, NV, NY, OR, SD, TX, UT, WI, WV, WY Logistic regressionAZ, WI Multinomial regression (for mode split)CT Nonparametric regressionFL, KY
Survey results Question 1: Please indicate the methodology(ies) used in your agencys program to estimate future traffic volumes. All responding states but fourColorado, Maryland, New Mexico and Pennsylvaniause linear regression models to estimate future traffic volumes. Seven states make use of multiple regression models: Arizona (least squares, linear, logistic) Connecticut (linear, multinomial) Florida (linear, nonparametric) Kansas (least squares, linear) Kentucky (linear, nonparametric) New Mexico (cubic, least squares) Wisconsin (Box-Cox, linear, logistic)
Survey results Question 1: Please indicate the methodology(ies) used in your agencys program to estimate future traffic volumes. Respondents reported other methodologies used to forecast traffic volumes, including: Growth rate from similar sites (Nevada) Historical trend analysis (Colorado) Linear or parabolic growth rates based on the knowledge of local growth patterns (Maryland) Statewide or travel demand models (Arizona, Maine, Massachusetts, North Carolina, Oregon, Wisconsin)
Survey results Question 1a: Does your agency use a modeling software program to estimate future traffic volumes? Only four statesColorado, Illinois, Kansas and South Dakotareport no use of modeling software to forecast traffic volumes. VendorModel/ProgramState Caliper CorporationTransCADIA, MS, MT, NV, WY CitilabsCube VoyagerMD, ME, NY, UT CititlabsTP+ (legacy system)MD, WI CitilabsTranplan (legacy system)CT IHS Global InsightStatewide VMT macroeconomic modelNY PTV AmericaVISUMNM Not specifiedStatewide or travel demand models KY, MA, MD, MI, MN, OR,TX
Survey results Question 2: How many years of historical data does your agency use when forecasting future traffic volumes?
Survey results Question 3: Please indicate the social and economic variables included in your agencys traffic forecasting methodology. Only four statesColorado, Florida, Missouri and Nebraskado not report the use of socioeconomic variables in forecasting models. Socioeconomic Variable Number of Responses Socioeconomic Variable Number of Responses Total population22Unemployment rate3 Employment21Motor vehicle registration3 Households21Fuel consumption2 Personal income9Driving age population2 Labor force6Population age 16 and over2 Gas prices4Population age 65 and over2
Survey results Question 3a: If socioeconomic variables are included in your agency's traffic forecasting methodology, please describe how they are employed. Socioeconomic variables most often serve as inputs to respondents travel demand or statewide models. Socioeconomic variables are also used to: Analyze trends. Determine impact on current traffic. Determine trip generation/trip distribution/trip attraction. Develop growth profiles. Influence choice of growth rate.
Survey results Question 4: When forecasting traffic volumes, does your agency apply minimum and maximum growth factors? States Using Minimum Growth FactorsStates Using Maximum Growth Factors State (14) Factor Percentage State (8) Factor Percentage AZ, MS, ND, NMNone specifiedAZ, MS, NM, WVNone specified OR0%MA1.5% KS, MA, ME, MN, NV, WI0.5%MN3% MO0.5 % to 1%MT3.5% MT1%TX5% TX2%
Survey results Question 5: Does your agency apply different growth rates to heavy commercial traffic versus total traffic volume? Twelve states apply different growth rates to heavy commercial traffic and total traffic volume. ArizonaNevada IllinoisNew Mexico KentuckyNew York MaineNorth Dakota MarylandOregon MichiganWisconsin AZ applies different factors at statewide modeling level, not at a micro level. NV has four methods for truck forecasting. NM uses data from FAF3 to forecast truck trips. OR uses different factors for its statewide integrated freight model.
Survey results Questions 6 and 6a: Please indicate the time periods included in your agencys projections of future traffic volumes and describe why these time periods were selected. Time Period Number of Responses Time Period Number of Responses 20 years265 years6 10 years1440 years5 30 years1235 years4 25 years1050 years1 15 years8 Reasons for selecting time periods: Pavement/project design (12 states) Required for long-range transportation plan (4 states) FHWA standards (3 states) Required for statewide model (3 states)
Survey results Question 7: Has your state experienced a flattening or decrease in VMT in nonmetropolitan areas? Twenty-three states are experiencing a flattening or decrease in VMT; seven states are not. Yes ReponsesNo Responses Arizona, Colorado, Connecticut, Illinois, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New York, North Carolina, Oregon, Pennsylvania, Utah, West Virginia, Wisconsin Florida, Montana, New Mexico, North Dakota, South Dakota, Texas, Wyoming
Survey results Question 8: If your state has experienced a flattening or decrease in VMT in nonmetropolitan areas, is your agency considering changes in the methodology used to forecast traffic volumes, or have changes already been adopted? Description of Traffic Forecasting ProgramState Flattening or Decrease in VMT and Considering Forecasting Changes CT, IA, IL, KS, KY, MA, MI, MN, NC, NY, OR Flattening or Decrease in VMT and Not Considering Forecasting Changes AZ, CO, MD, ME, MO, MS, NE, NV, PA, UT, WI, WV No Flattening or Decrease in VMTFL, MT, ND, NM, SD, TX, WY
Survey results Question 8: If your state has experienced a flattening or decrease in VMT in nonmetropolitan areas, is your agency considering changes in the methodology used to forecast traffic volumes, or have changes already been adopted? States are considering or making changes in: Growth rates Statewide models
Summary Thirty-one states responded to our request (30 online surveys completed) Most of the responding states use linear regression models to estimate future traffic volumes. Less commonality is found in the software models states use to estimate future traffic volumes. Most respondents use socioeconomic variables, most often as inputs to travel demand or statewide models. Survey results indicate that many other states are also experiencing a flattening or decrease in VMT. Almost half of these states are considering or implementing changes in forecasting methods.