Traffic Impact Analysis (TIA)

TIA requirements in the Dallas-Fort Worth metroplex vary by city, with each municipality maintaining its own thresholds, submittal requirements, and review processes. Core DFW markets including Dallas, Fort Worth, Arlington, Plano, Frisco, McKinney, Richardson, and Irving each have distinct development review procedures. In North Texas growth communities such as Prosper, Celina, Allen, Denton, Lewisville, Grapevine, Carrollton, Addison, and Rockwall, requirements continue to evolve as these cities update their development codes to manage rapid growth.

Most DFW cities require a TIA when a development generates between 100 and 200 peak-hour trips, though some fast-growing communities have adopted lower thresholds or screening worksheets. Fort Worth and Dallas each maintain their own traffic study guidelines, and many suburban cities reference or adapt those frameworks. Projects with access on TxDOT-maintained roadways may also require coordination with the TxDOT Dallas or Fort Worth district, which runs as a separate review path parallel to the municipal process.

Gradient can help confirm the specific TIA trigger, required scope, and reviewing agency for your DFW project before the study begins.

The City of Houston classifies TIA studies into four categories based on new peak-hour trips on the adjacent street: Category I (fewer than 100), Category II (100–499), Category III (500–999), and Category IV (1,000+). Category II through IV studies require a preliminary scoping meeting with the City Traffic Engineer before the study begins. Trip generation must use the current ITE methodology, and City of Houston TIA submittals must bear the seal and signature of a Texas Licensed Professional Engineer.

Since January 1, 2021, all newly submitted TIAs are checked against the City’s TIA Content Guide and OCE Format Requirements for administrative completeness — review will not begin until the TIA passes this check. Analyses must typically use Synchro or City-approved software, and the study scope may include safety, circulation, transit, neighborhood traffic impacts, and pedestrian and bicycle access. The process begins with the City’s Access Management Form (Form A).

Common delay points in Houston include submitting a TIA before the Access Management Form is reviewed, missing scoping exhibits, using unsupported trip-generation assumptions, or not including electronic traffic-count and model files. Across the Houston metro, Sugar Land typically triggers a TIA at approximately 100 peak-hour trips, 1,000 daily trips, or projects involving 100+ acres. Fort Bend County maintains its own TIA guidelines separate from the municipalities.

Full Houston TIA requirements, study categories, submittal sequence and review timelines →

Austin is the Texas outlier: it sizes the requirement on daily trips rather than PM peak-hour trips alone. A study is triggered above 2,000 net new unadjusted daily trips, and the City layers on a mandatory TDM plan and a Street Impact Fee that changed how mitigation is assigned. Surrounding cities and counties do not follow Austin's Transportation Criteria Manual and set their own thresholds, usually peak-hour based.

Full Austin TIA requirements — study tiers, the Determination Worksheet, Street Impact Fee, reviewers and suburban rulebooks →

San Antonio generally requires a TIA when a development generates 76 or more peak-hour trips, per UDC Section 35-502 — lower than the 100-trip standard used by many Texas cities. Projects under 76 peak-hour trips may still need a Peak Hour Trip Generation Form and Turn Lane Assessment. Study levels are grouped as 76–250, 251–1,000, and 1,001+ peak-hour trips, each with increasing scope requirements.

San Antonio’s process is tied to proportional mitigation, meaning the TIA does not just identify improvements — it also supports the calculation of what improvements are attributable to the development. A TIA scoping meeting determines study area, trip generation methodology, trip distribution, analysis scenarios, and background growth rates. Turn lanes may be required at driveways or streets with 500 daily entering right/left-turn trips or 50 peak-hour entering turn trips, even for projects below the 76-trip threshold. Note that downtown, IDZ, commercial retrofits, and TND/TOD projects may have different treatment under the UDC.

Surrounding communities including New Braunfels, Schertz, Boerne, and Converse each maintain their own thresholds and review processes. Bexar County also has review requirements for developments in unincorporated areas.

El Paso requires a TIA for developments within city limits and ETJ expected to generate more than 1,000 average daily trips or more than 100 peak-hour trips, per Title 19 (Section 19.18.010). Trip generation must use the latest ITE Trip Generation Manual or locally approved rates. The TIA must be signed, sealed, and dated by a Professional Engineer and is reviewed by applicable city review staff.

A waiver may be requested if prior traffic studies exist or improvements are already in place. For rezoning applications, trip generation is based on the maximum land-use intensity allowed under the proposed zoning, not only the applicant’s current concept plan. El Paso may defer the TIA to subdivision stage if the property is not platted and the project generates fewer than 500 peak-hour trips. An alternate traffic-impact calculation may be considered for projects under 500 peak-hour trips if nearby roadway and intersection LOS is A–D and no safety issues are present.

Texas cities do not use one uniform TIA threshold. Some cities use daily-trip thresholds, some use peak-hour thresholds, and some require a threshold worksheet before determining the study level. San Marcos screens for 300+ daily trips on residential streets or 2,000+ daily trips on non-residential streets. Corpus Christi uses a 501+ weekday peak-hour trip trigger for certain site plan or street closure applications. Other mid-size cities such as Waco, Lubbock, Amarillo, Midland, Odessa, and Laredo each maintain their own requirements.

If access is on a state-maintained roadway, TxDOT may require an access-related engineering study, technical memo, or formal TIA depending on trip generation, access type, roadway context, and district review. TxDOT access review creates a separate review path that runs in parallel with the municipal process.

California TIA requirements typically involve two separate questions: CEQA transportation impact, which is usually VMT-based since SB 743 took effect statewide on July 1, 2020, and local operations/access review, which may still require LOS, queuing, driveway, parking, loading, or safety analysis.

Projects within one-half mile of a major transit stop or high-quality transit corridor are generally presumed to have a less-than-significant CEQA transportation impact. Gradient can help confirm the applicable CEQA, local agency, and Caltrans review path before the study is scoped.

WSDOT reviews land use development proposals, SEPA submittals, driveways, and access connections affecting state right-of-way. SEPA review can require transportation-impact documentation even when the local TIA threshold is not the only trigger.

Washington studies often become multimodal early because WSDOT and local agencies may look at safety, transit access, pedestrian and bicycle connections, driveway spacing, and neighborhood circulation — not just vehicle delay. Gradient can help determine whether the project needs local SEPA transportation documentation, WSDOT access coordination, or both.

Colorado projects often split between local entitlement review and CDOT State Highway Access Permit review. If the project changes access to a state highway or materially changes traffic using an existing access, CDOT may require a Traffic Assessment.

CDOT uses Traffic Assessment Levels to determine the appropriate study type based on design-hourly traffic volume and site-specific access conditions. Municipal TIA requirements vary across Colorado, with each jurisdiction setting its own thresholds and review processes. Gradient can help navigate overlapping municipal and CDOT access requirements before the study is scoped.

IDOT requires permits for work within state-maintained roadway right-of-way, and district requirements vary — early district coordination matters. For larger access permits involving signals or turn lanes, the study can involve kickoff meetings, AM/PM analysis, safety review, non-motorized impacts, turn-lane warrants, signal warrants, and a 20-year design scenario. These larger permits can have review timelines of 9 to 14 months from first submission to permit issuance.

In Chicago, CDOT maintains separate Traffic Impact Study guidelines for development review. Gradient can help coordinate early IDOT district outreach and confirm whether local or state review — or both — applies to your project.

MDOT SHA requires a Traffic Impact Study for proposed development or redevelopment generating more than 50 peak-hour trips, or when a project is expected to directly affect traffic operations on state roads. SHA studies evaluate capacity, signalization, safety, and multimodal issues, usually in connection with an access permit.

Maryland can involve overlapping reviews: local Adequate Public Facilities Ordinance (APFO) review plus MDOT SHA access review when state roads are affected. This is especially common in Montgomery County, Prince George’s County, and Baltimore-area suburbs. Gradient can help coordinate overlapping local APFO and MDOT SHA access reviews when both apply to your project.

Yes. Gradient supports TIA and transportation-impact work outside Texas where our licensing and project team align with the jurisdiction’s requirements. Because thresholds and sealing requirements vary by state, we confirm the applicable city, county, and state DOT review path before scoping the study.

We currently hold licenses in 16 states, including Texas, California, Washington, Colorado, Illinois, and Maryland. Contact us with your project location and we can confirm whether we can support your jurisdiction.