Austin Traffic Impact Analysis (TIA)

The City of Austin bases its TIA requirement on net new daily vehicle trips rather than peak-hour trips. Under Section 10 of the Transportation Criteria Manual (TCM), a development that generates more than 2,000 net new daily trips must submit a study, and the type scales with size:

A Transportation Assessment (TA) is required for developments generating roughly 2,000 to 4,999 unadjusted daily trips, and a full Transportation Impact Analysis (TIA) is required at 5,000 or more. Projects below 2,000 daily trips generally complete a trip-generation determination rather than a full study. Gradient Systematics runs the trip-generation determination first so you know exactly which tier applies before committing to a scope.

Austin's Street Impact Fee (SIF) — adopted in 2020 and assessed on development since 2022 — is a one-time charge based on a project's intensity and land use that funds roadway-capacity improvements across the city. The "SIF Max" calculation replaced the older rough-proportionality method for determining a development's share of roadway costs.

In practice, the Street Impact Fee often covers the network-capacity mitigation that a TIA previously assigned to a developer, while the study still identifies the site-specific improvements — turn lanes, driveways, signals — needed for safe and efficient access. We scope the TIA so it aligns with the SIF assessment, so you are not paying for the same impact twice.

Yes. Austin's requirements go further than most Texas cities. A Transportation Demand Management (TDM) plan is required for all developments generating 2,000 or more daily trips, and TDM measures such as transit access, bicycle facilities, and parking management can earn vehicle-trip reductions that lower the study's analytical burden.

This reflects the Austin Strategic Mobility Plan (ASMP) and its 50/50 mode-share goal — the City expects studies to consider pedestrian, bicycle, and transit access alongside vehicular capacity, not just level of service. Gradient Systematics prepares the multimodal and TDM components as an integrated part of the study rather than an afterthought.

Which agency reviews your study depends on the site's location and roadway access. Austin Transportation and Public Works — Transportation Development Services (TDS) reviews studies inside city limits and in Austin's extraterritorial jurisdiction. Travis, Williamson, and Hays Counties review projects in their unincorporated areas. Surrounding cities such as Round Rock, Cedar Park, Georgetown, Leander, Kyle, Buda, and San Marcos each run their own municipal review.

For access to a state-maintained roadway, the TxDOT Austin District reviews the study for a State Highway Access Permit, and where a tollway is involved the Central Texas Regional Mobility Authority (CTRMA) may also weigh in. A single project near a jurisdictional or corridor boundary can trigger several of these reviews at once, which is why we map out every reviewer during scoping.

The suburbs do not follow Austin's Transportation Criteria Manual. Each city sets its own thresholds and process: Round Rock and Cedar Park in Williamson County, Kyle, Buda, and San Marcos in Hays County, and Georgetown and Leander on the northern edge each maintain distinct traffic-study requirements, often tied to peak-hour trips rather than Austin's daily-trip model.

The Street Impact Fee and TDM requirements are specific to the City of Austin and do not automatically apply outside its limits. Projects on the metro fringe — especially fast-growing corridors in Williamson and Hays Counties — frequently sit under a suburban city's review, a county's review, and TxDOT all at once. We confirm the governing jurisdiction before scoping so the study matches the right rulebook.

Any new or modified access to a state-maintained roadway requires a TxDOT Austin District State Highway Access Permit. The corridors that most commonly bring TxDOT into a project include I-35, MoPac (Loop 1), US-183 and the Bergstrom Expressway, US-290, SH-71, RM 620, and RM 2222.

Several of the region's major routes are tolled and operated by the Central Texas Regional Mobility Authority — including 183A, the 290 Toll, the MoPac Express Lanes, and SH 45SW — which adds a second layer of coordination for sites fronting those facilities. We handle access permit scoping, driveway spacing, sight distance, and turn-lane warrants with both agencies in a single PE-sealed study.

Timelines depend on the reviewing agency and the study tier. City of Austin TDS reviews typically run several weeks per cycle, and because Austin studies include TDM and multimodal components, the first review often carries more comments than a conventional vehicular-only study — building time for one or two comment rounds into the schedule is prudent.

County reviews in Travis, Williamson, and Hays are broadly comparable, while TxDOT Austin District reviews for State Highway Access Permits generally take longer where turn-lane design or signal warrant analysis is involved. When a project needs both local and TxDOT approval, we run the reviews concurrently so the overall schedule is governed by whichever review takes longest.