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WSDOT Traffic Forecasting Guide. Volume 1– Introduction to the Forecasting Process


The Washington State Department of Transportation has produced this guide to improve the development of traffic forecasts used by Department engineers and planners. The guide is intended to help standardize the methodology for developing forecasts, provide an "audit trail" of the steps and assumptions behind each forecast, and ensure that the assumptions underlying the forecasting process have been carefully considered.

The guide is split into two volumes. The first volume describes the forecasting process and reviews the issues that must be addressed. The second volume provides detailed instructions for the forecasting process.

Volume 1 contains background information on the steps involved in forecasting and the factors that must be considered as part of a traffic forecast. It should be used to introduce staff to the traffic forecasting process. It will also help identify the resources required to forecast traffic and then assist in analyzing and applying those resources.

Volume 2 of the guide contains a more precise description of how to perform the forecast. In addition, the Volume 2 appendices contain copies of the worksheets that should accompany any forecasts engineers perform, and instructions on using several Lotus 1-2-3 spreadsheets that were designed to ease the forecasting process. Lastly, Volume 2 contains a copy of the Lotus 1-2-3 templates for use by engineers and planners.


  • Date Published: May, 1991
  • Publication Number: WA-RD 219.1
  • Last Modified: September 26, 2007
  • Author: Mark E. Hallenbeck.
  • Originator: Washington State Transportation Center (TRAC)
  • # of Pages: 127 p., 2,990 KB (PDF)
  • Subject: Engineers, Planning and design, Traffic estimation, Traffic forecasting, Transportation planning, Travel demand.
  • Keywords: Traffic forecasting, forecasting, transportation planning.
  • Related Publications: WSDOT Traffic Forecasting Guide. Volume 2 – Forecasting Instructions, (WA-RD 219.2).

This abstract was last modified April 29, 2008