Traffic Forecasting dates back to the 1930s when the Bureau of Public Roads first started the federal financing of highway projects. From the very beginning, traffic counts were collected and growth rates were applied to produce a travel demand forecast used for planning and design purposes. The purpose of traffic forecasting is to produce future estimates of average daily traffic (ADT), design hour volumes (DHV) and truck percentages (TD and T24) for use in design and planning.

The need for certified traffic forecasts was originally dictated by a directive from the FHWA and is specified in Section 102 of the Location and Design Manual. (Section 102 - Traffic Data, states, “All traffic data used shall be certified by the Office of Technical Services.”)

Certified traffic is also referenced in several key ODOT design documents as follows:

• State Highway Access Management Manual (Version 8-15-03) - (Section 5.5.5)
• Location and Design Manual (revised Oct. 2008) - (Section 102 and Section 550)
• Traffic Engineering Manual (April 17, 2009) – (Section 402-2 – Traffic Volumes)

Modeling & Forecasting develops certified traffic forecasts for projects and reviews forecasts developed by others. Traffic forecasts developed by Modeling & Forecasting utilize the methodology discussed in NCHRP 255. Certified traffic is typically requested by Central Office and District Personnel.