Traffic Impact Analysis

What is a traffic impact analysis?

Local governments – towns, cities, counties, and states – have a responsibility to ensure public health, safety, and welfare. For new development, redevelopment, and rezoning projects, these responsibilities are managed through various planning and engineering review processes, including the review of the potential “traffic impacts”. Because new developments typically “generate” additional vehicle trips that use will use public roads, a traffic impact study, commonly referred to as a TIS or TIA, is used to help determine the extent of these impacts. In general, a traffic impact study provides a review of:

Existing conditions

The proposed development, site access, and circulation

Effects of new trips on roadways and intersections

How do I know if I need a traffic impact analysis?

The following minimum thresholds require a traffic study: 

a. Additional average daily trips generated by the development exceed 500 trips per day, as determined by the ITE Trip Generation manual.

b. Additional PM peak trips generated by the development exceed 100 trips per hour, as determined by the ITE Trip Generation manual.

c. Any residential development that exceeds 150 new dwelling units. 

d. The development will cause the adjacent streets or closest intersection(s) to operate at a reduced Level of Service.

e. The adjacent street or closest intersection(s) already operates at LOS F.