San Antonio Traffic Impact Analysis (TIA)

The City of San Antonio determines TIA requirements under Section 35-502 of the Unified Development Code (UDC), based on the number of peak-hour trips (PHT) a development generates. Rather than a single fixed number, the process starts with the applicant completing a trip-generation analysis (the City's TIA Threshold Worksheet) to determine which level of submittal applies.

Smaller developments may only need a PHT generation form or a limited turn-lane analysis, while larger developments require a full TIA report. At 76 or more peak-hour trips, turn-lane analysis is folded into the full TIA rather than handled separately. For developments requiring a detailed study, the City holds a scoping meeting with Public Works and Development Services staff to set the study area and methodology. Gradient Systematics runs the threshold analysis first so you know exactly which submittal level applies before committing to a scope.

San Antonio is distinctive in that UDC §35-502 pairs the Traffic Impact Analysis with a Roughly Proportionate Determination Study. Under Texas law, a city can only require a developer to fund infrastructure improvements that are "roughly proportionate" to the impact of the development. The RP study documents that fair-share calculation.

In practice, the TIA identifies the roadway improvements a development triggers, and the RP determination establishes how much of that cost the developer is legally obligated to bear. Getting both right in the same submittal protects you from being asked to over-improve — and keeps the negotiation with the City grounded in defensible engineering. We prepare the TIA and RP determination together so the two align from the start.

Inside the city, TIAs are reviewed by the City of San Antonio's Public Works Department — Transportation Plan Review, in coordination with the Development Services Department (DSD) that handles the underlying platting or site plan. (In 2022 the City split its former Transportation & Capital Improvements department into separate Transportation and Public Works departments, so current submittals route through Public Works.)

Bexar County reviews projects in its unincorporated areas, and the TxDOT San Antonio District reviews any access to a state-maintained roadway for a State Highway Access Permit. Surrounding cities such as New Braunfels, Schertz, Boerne, and Seguin run their own municipal review. A single project near a jurisdictional boundary can trigger several of these at once, which is why we map every reviewer during scoping.

San Antonio's explosive north-side growth has concentrated along the US-281 and Loop 1604 corridors, where traffic volumes have outpaced roadway capacity for years. As a result, TxDOT and the City scrutinize driveway spacing, turn-lane warrants, and access location on these corridors more heavily than almost anywhere else in the metro.

Commercial sites competing for frontage along US-281, Loop 1604, I-10, and Bandera Road (SH-16) frequently face restrictions on where — and whether — a new driveway can connect, along with requirements for deceleration lanes, median treatments, or shared access. Getting the access strategy right early is often the difference between an approvable site plan and a costly redesign. We coordinate access management with the TxDOT San Antonio District from the first scoping conversation.

Much of San Antonio's north and northwest growth sits over the Edwards Aquifer Recharge Zone, where impervious-cover limits and water-quality regulations shape how much of a site can be developed and how stormwater is managed. While these are environmental rather than traffic rules, they directly influence site layout, parking, and driveway placement — which in turn affect the trip distribution and access design a TIA evaluates.

Projects in the recharge zone often carry lower development intensity or altered site geometry, and coordinating the traffic study with the site's environmental constraints avoids rework. Gradient Systematics scopes north-side studies with these overlays in mind so the access and circulation plan works within the site's real buildable footprint.

Any new or modified access to a state-maintained roadway requires a TxDOT San Antonio District State Highway Access Permit. The corridors that most commonly bring TxDOT into a project include I-35, I-10, I-37, US-281, US-90, Loop 410, Loop 1604, SH-151, and Bandera Road (SH-16).

For sites fronting these routes, TxDOT evaluates driveway spacing, sight distance, turn-lane warrants, and operational impact on the state facility — often alongside a concurrent City of San Antonio or Bexar County review. We prepare a single PE-sealed study scoped to satisfy both the local agency and the TxDOT San Antonio District.

Timelines depend on the reviewing agency and the study's complexity. City of San Antonio Transportation Plan Review cycles typically run several weeks each, and because the process includes both the TIA and the Roughly Proportionate determination, allowing time for one or two comment rounds is prudent — especially on access-managed corridors where turn-lane and driveway details draw close review.

Bexar County reviews are broadly comparable, while TxDOT San Antonio 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.