The National Academies

NCHRP 08-153 [Anticipated]

Guidance on Improving Truck Traffic Estimates in Design Traffic Forecasts

  Project Data
Source: AASHTO Committee on Planning
Funds: $425,000
Staff Responsibility: Jennifer L. Weeks
Fiscal Year: 2022

This project has been tentatively selected and a project statement (request for proposals) is expected to be available on this website. The problem statement below will be the starting point for a panel of experts to develop the project statement.

The 2020 “INVEST in America Act” directs state department of transportation (DOTs) to develop tools and databases for better informed passenger and freight planning. The current practice on determining “Design Traffic” forecasts to assess roadway design elements stands in contrast with “Planning Level” forecasts used for identifying possible deficiencies that also form input to determining roadway design elements.

Planning forecasts use historical traffic counts, existing and future land use, road network changes, population and employment estimates. Design level traffic analysis requires a much more precise level of detail at the link level and should include turning-movements data as shown in the figure to the left.

Furthermore, a model’s truck traffic forecast is generally a secondary step that is represented as a percentage of traffic after the overall traffic is determined. When projecting future truck volumes under the design forecast, often the same percentages of truck traffic identified under the existing conditions are applied to future Annual Average Daily Traffic and Design Hourly Volumes to forecast future truck volumes.

This research is intended to explore the best practices of “design level” forecasting of truck volumes in the roadway project development process. The results should facilitate better project evaluation, prioritization and implementation, traffic estimation, and design of roadway improvements.

Improvements in truck volume forecasts in “Design Traffic” Forecasting will enhance state and regional freight system planning, improve the project-level analysis on truck traffic management, and better accommodate the rapid growth in truck volumes due to a variety of reasons including online shopping. Traffic and design planners in state DOTs and MPOs will benefit from the outcome of the research and the resulting guidelines.

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