Since I’ve worked as an intern, I’ve always wondered what the traffic analyst, a transportation engineering major who just graduated, at our work does, although I understood that Traffic Impact Studies — often referred to as “the TIS” for a project — were required for projects that potentially impacted traffic within the cities or counties.
The Guidelines for Traffic Impact Studies in the City of Fresno (linked below) can be used an example. This document includes criteria used to determine if TIS’s are required on a project. Projects that need TIS’s require a traffic analysis to be performed based on the traffic conditions as set by Fresno’s current 2025 General Plan. The Traffic Engineering Department recommends Synchro, a traffic simulations software, for analysis for the TIS. There are many details mentioned that reinforce the document’s main assertion that the guidelines are meant merely as a guide and that only an experienced traffic engineer can address the problems necessary to provide efficient transportation within the area. For example, in Downtown Fresno, a TIS is not required because any development would not hamper the traffic more than the close-proximity that the traffic lights downtown already slow down and stop traffic. In traffic analysis models, it is generally required to model the effect of the development on traffic within a 2 mile radius of the project site (according to what I learned about at work), with the traffic based on the peak hour traffic, or trip generation as it is referred to, at the particular location. Access into the development as well as circulation through it is another component needed to be addressed. Last of all, the format required of the TIS is outlined so that a reviewer at the City of Fresno can more quickly look through it.