Traffic Impact Studies: Understanding when and why you need them

A proposed land development, redevelopment or rezoning project requires Traffic Impact Studies to evaluate whether transportation infrastructure can support additional trips a project will generate. For developers and municipal stakeholders, Traffic Impact Studies provide critical information about land use and planning decisions. Below, we discuss the importance of Traffic Impact Studies and how partnering with an experienced team of engineers and environmental consultants can help with building or improving transportation infrastructure.

The importance of Traffic Impact Studies: Why and when you need them

A land development plan that generates traffic, such as a shopping mall, will have many stakeholders. Residents are curious how construction and the proposed development will affect their daily lives. Developers must understand required mitigation measures or improvements, along with cost implications. The municipality must answer the public's questions regarding the project's environmental impact, prepare related environmental studies and ultimately decide whether to approve the project. Finally, public works and state transportation agencies need site-specific information to design the facilities and approve access. Traffic Impact Studies provide important information to help all stakeholders understand and evaluate the project.

Why do you need Traffic Impact Studies?

Traffic Impact Studies vary in detail and complexity depending on the type, size and location of a development project. Nonetheless, the objective of every Traffic Impact Study is the same. Traffic Impact Studies review:

  • Site conditions.
  • The proposed development.
  • Site access and circulation.
  • How trips generated by the development will affect roads and intersections.

Traffic Impact Studies not only evaluate the effects of a particular set of developments but also provide information on broader development plans and decisions that affect overall community growth patterns and characteristics. Key reasons to conduct Traffic Impact Studies include:

  1. Identifying potential transportation infrastructure problems. Traffic Impact Studies forecast the additional traffic associated with a development and identify potential problems that might influence development decisions. In large communities, these assessments help plan for multimodal transportation, including public transit.
  2. Determining improvements to accommodate the development. A Traffic Impact Study helps reduce the negative effects the proposed development could have on the neighboring community. It ensures the transportation network can accommodate the expected traffic increase.
  3. Ensuring safe and reasonable traffic conditions. Safety is a top priority for any land development project. A Traffic Impact Study helps ensure safe and reasonable traffic conditions once the development is complete. This protects the community's substantial investment in its street system. The study may also recommend geometric or operational roadway improvements.

When do you need Traffic Impact Studies?

Site development and review processes are governed by guidelines, policies and ordinances established by local governments. In most cases, the primary requirement to perform a Traffic Impact Study is based on the number of trips generated by the site, the type and size of the development and other site characteristics. A common baseline requires a Traffic Impact Study when a proposed land development generates 100 trips to the adjacent street network during the peak traffic hour.

Not all projects require a detailed Traffic Impact Study. Based on the type and size of the development, a Traffic Impact Study can vary from a cursory review and a letter of opinion from a qualified professional to a comprehensive analysis and report that includes details about the area-wide transportation system and other planned or approved developments in the vicinity.

In some cases, the local government performs the Traffic Impact Study. However, this is not a common practice, so municipalities and developers often need to find qualified transportation professionals to conduct a Traffic Impact Study. The transportation operations and design work also requires a qualified and experienced professional engineer's supervision.

Preparing Traffic Impact Studies for developments of all types and sizes

At Fehr Graham, our qualified team of engineers and professionals have expertise in traffic and transportation engineering and planning. In addition to expertly prepared Traffic Impact Studies, our transportation engineering solutions include developing road, bridge and rail designs, pavement management, construction management, environmental documentation and funding solutions.

To learn more about working with Fehr Graham to conduct Traffic Impact Studies for your community, contact us us or call us at 815.562.9087.

As the firm’s Lead Transportation Engineer, Fehr Graham Principal Noah Carmichael, PE, leads notable, complex and high-profile transportation infrastructure engineering projects. He works closely with municipal and governmental partners on public infrastructure planning and identifies funding opportunities to support community capital investment goals. Reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..