PUBLICATIONS

A Traffic Impact Study Report or a Traffic Brief

I have seen some authority agencies struggling when deciding whether a full traffic impact study report or a traffic brief is required for a proposed site (including expansion). Of course, it seems to be safer asking for a traffic impact study report but what if not necessarily needed.

It seems that municipalities have their own thresholds but no guidance in those thresholds are found in the municipal documentation; as a result, it provides the impression that the decision and criteria is determined by the agent in turn. The lack of these thresholds bring sometimes the disagreement between the proponent and the authority agency.

In fact, a traffic impact study is not necessary for every development as some developments are unlikely to generate significant traffic. Thresholds should be established by municipalities based on local needs and they may vary from an agency to another; however, there are some guidance to take into account.

The “Transportation Impact Analyses for Site Development”, an ITE publication, provides baseline guidelines to help determining the need for a traffic impact analysis, one of them is the generation of additional 100 vehicles per hour by the proposed development which can create some issues if not well attended. The publication also indicates that not always the 100 vehicle per hour should be seen as a strict threshold because many jurisdictions in densely populated areas tend to use lower thresholds for initiating a transportation impact analysis.

When the development might generate fewer trips than the established threshold, analysis of localized issues may be needed and reported in a traffic technical letter instead of a full traffic impact study. Some of the perceived issues might include:

• Existing high traffic volumes on adjacent roads that may affect access (in/out) to the development.
• High rate of accidents in the adjacent road(s) or intersection(s).
• Inadequate sight distance at access points.
• Lack of existing left turn lanes on the adjacent road at the proposed access.
• Any other specific problem or deficiency that may be affected by the proposed development.

As transportation/traffic engineers, we are able to help in the scoping of work because not every proposed development or expansion requires a full report but authority agencies should consider have those thresholds available to comply with the requirements.

Asurza Engineers Ltd – www.asurza.ca – Ontario, Canada

Traffic and Transportation Engineering