California Department of Transportation

Project Development Workflow Tasks (PDWT)

Part 3 - Identify Project Need and Project Initiation Document

II. Project Initiation Document

B. Develop Initial Alternatives (150.10) - Develop Concept Alternatives (WBS 150.10.15)

P46. Request Preliminary Geo-technical Design Report

High accident concentration locations are systematically investigated by the Traffic Operations Division to determine probable causes and to consider the most effective, lowest cost corrective measure for each specific situation.

A detailed analysis of accident history, collision diagrams, field investigations, and a review of roadway geometrics assist in identifying accident patterns that may be susceptible to correction. The surveillance engineer will also look for an accident pattern and try to find common elements such as time of day, direction of travel, type of collision, movement preceding collision, weather, object struck or other associated factors.

Investigations are documented on the Traffic Investigation form “HT65” and include an appropriate recommended corrective action. The investigation’s collision diagrams are useful to the Engineer in determining common accident patterns, and for developing appropriate solutions. Most of the information contained in the HT65 is confidential and may not be reproduced in any report. The information is to assist in identifying areas of concern.

A project engineer may obtain a HT-65 accident investigation from the District Traffic Investigations Branch, if one has not already been performed.

Time Constraint:

If an HT65 report was not generated for a particular area during the normal quarterly review, one may be requested. It may require up to 2 months to complete.


Traffic Safety Guidelines, (Chapter 3.0, “Accident Surveillance System” )


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This page last updated October 20, 2010