Traffic Study 101: Vital to Your Commute

Traffic Study 101: Vital to Your Commute

The property is well-priced, preliminary layout has been defined, and the tenant is ready to proceed when someone in a meeting says, “We’ll need a traffic study.”

Both new development and redeveloped sites often trigger the need for a traffic study.  As a civil engineering firm, here are some of the most frequent questions we get in regard to traffic studies.

Why is a Traffic Study Needed?

Project changes typically add or alter traffic patterns, which ultimately impact the surrounding transportation system. The primary function of a street network is to provide for the safe and efficient movement of all modes of transportation. A traffic study serves several purposes:

  • Reviews overall site access and circulation
  • Proposes means to maintain satisfactory transportation levels of service
  • Helps to ensure safety for all users
  • Communicates projected development traffic impacts

What Level of Traffic Study do I Need?

Most cities allow commercial applicants to submit a study that fits the size of their proposed improvement. The requirements are based on estimated trips in a peak hour as established by the Institute of Transportation Engineers (ITE) Trip Generation Manual. The Manual provides data for almost 200 land uses based on items such as building square footage and number of employees. For example, a 67,000-square foot general office building, or 90 single family homes will generate around 100 peak hour vehicle trips.

Different trip generation totals function as a base guideline for triggering different levels of study requirements:

  • Basic Traffic Study (< 100 trips / peak hour): Estimate trip generation, evaluate proposed site access, review internal circulation dimensions, and make recommendations accordingly.
  • Standard Traffic Study (100-500 trips / peak hour): AM and PM peak hour traffic counts (or other times of concern) are typically required. Twenty-four hour counts may be necessary for certain sites. Existing traffic will be added to site trip generation to develop existing plus development traffic exhibits for the impacted street network. The exhibits are then analyzed intersection by intersection to determine the level of service impacts of the proposed development. Agencies also may ask for future traffic projections, adding another layer of analysis. This exercise leads to recommendations of appropriate safety and capacity improvements.
  • Extended Traffic Study (> 500 trips / peak hour): Developments generating this much traffic are usually asked to cast a wider net that includes intersections and roadways beyond the immediate site.


Who Should Prepare a Traffic Study?

Traffic studies should be completed by a qualified and experienced transportation engineer. Those certified as a Professional Traffic Operations Engineer (PTOE) are preferred by most cities. These professionals have working knowledge of circulation design standards and regional access management policies. This knowledge can save a developer several design iterations and streamline the review process.

What Does a Traffic Study Cost?

There is no “typical” cost for a traffic study since each site is unique in scope and highly sensitive to local traffic. A traffic study can range in cost from a few thousand dollars to tens of thousands of dollars based on the complexity and extent of the study.

A basic traffic study without the need for traffic counting can be complete in one or two days. Standard traffic study costs are highly dependent upon the data collection and analysis requirements brought on by the site and reviewing agency.

Did We Really Need to do This Study?

Yes.  Everyone has been stuck at a traffic signal, or in the parking lot of a shopping center or restaurant.  And we would bet, most everyone has used that time to wonder “Why isn’t there an additional lane here?” or “Why isn’t there a turn lane there?” Moments like that are a small example of exactly why traffic studies are so important and useful to our everyday life.

While traffic is largely viewed negatively, it is truly a sign of prosperity. Traffic studies provide a process for agencies to better manage overall access and review development traffic impacts. Their ultimate goal: to make traffic safe and efficient for all.

David Smalling Public Works Project Manager

David Smalling Public Works Project Manager





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