When & How to Start a Traffic Impact Analysis

An applicant or applicant’s consultant must identify their jurisdiction depending on the location of the proposed development. In larger jurisdictions, a TIA determination worksheet may be required. The TIA determination worksheet contains details regarding the proposed development including project location, land use, density, access points, and phases of construction. The TIA determination worksheet also contains estimates of the trip generated by the proposed development. The estimate of trip generation should be based on the latest edition of the Institute of Transportation Engineers (ITE) Trip Generation Manual.

The estimated trips quantified in the determination worksheets are usually evaluated by each jurisdiction to determine if a TIA is required. Exhibit 1 shows TIA determination requirements in some jurisdictions within Austin Metro Area.

*It is important to note that later this year (2021), the City of Austin may only require a smaller traffic assessment that focuses more on sustainable modes and Transportation Demand Management (TDM) for developments that generate less than 5,000 trips per day. Developments that generate over 5,000 trips per day will be required to complete a full TIA. These changes were prompted by the City of Austin’s Street Impact Fees (SIF).

A Traffic Impact Analysis is required if the proposed development is expected to surpass the trips per day thresholds shown in Exhibit 1. Each jurisdiction has its own guidelines to start with the TIA process. A Traffic Impact Analysis scope of work should be drafted by the applicant and submitted to the jurisdiction for approval prior to starting the TIA. It is important to mention that some jurisdictions have TIA fees associated with scoping and reviewing TIAs. 

Each jurisdiction has guidelines regarding the minimum requirements that must be included in a TIA Scope of Work. Minimum requirements shall include the location of the proposed development, land uses and density of the proposed development, location of the proposed driveways, construction phases, estimated traffic growth per year, trip reductions, and a list of existing and future intersections to be analyzed.  

Jurisdictions such as the City of Austin, provide a TIA Scope of Work template with specific guidance that will help to identify the objective of the study, the location of the intersections within the study area, and the requirements of the analysis. Additional information required to develop the City of Austin TIA Scope of Work includes estimated trip rates, peak hour trips, daily trips generated by the proposed development, a list of background projects in the vicinity of the proposed development, and trip distribution worksheets.  

Smaller jurisdictions such as the City of Georgetown, have sub-consultants to help in the TIA scoping and review process. RPS Infrastructure assists the City of Georgetown with these things. If the City of Georgetown Development Services engineers establishes that a TIA is needed based on thresholds, applicants can reach out directly to RPS traffic engineers to assist in the TIA scoping process. 

A Traffic Impact Analysis will not be reviewed by any jurisdiction without a pre-approved TIA scope of work. Exhibit 2 shows the TIA Administrative Requirements and how to start the TIA scoping process in some jurisdictions within Austin Metro Area.