Planning commission presses engineers on traffic‑study timing, TxDOT delays

Sean Spivey, an engineer with Collier's Engineers, told the Cibolo Planning & Zoning Commission during a June training that a traffic impact analysis (TIA) estimates how many trips a development will generate, where they will go and what mitigations might be required.

"We're basically looking at how much traffic a new development is likely to generate and then where those cars are going," Spivey said, explaining that common triggers for a TIA include roughly 76 peak‑hour trips, 1,000 daily trips or projects larger than 100 acres. He said the city typically applies the most conservative trigger when the UDC and the Transportation Criteria Manual differ.

The presentation covered trip generation (using the Institute of Transportation Engineers manual), level‑of‑service scoring (A–F), and common mitigations such as turn lanes and signals. Spivey said the city requires developers to fund TIAs and that mitigation timing often depends on phasing: some improvements may be built once a subdivision reaches a given lot count rather than all at once.

Commissioners pressed staff on several practical concerns. Commissioner Jacqueline Garcia asked why some TIAs and required mitigations take years to produce visible changes on the ground, citing the unactivated signal at the Turning Stone/Mesa intersection. A city engineering representative answered that signals on state roads require TxDOT approval and sometimes donation agreements, and that TxDOT staffing and approvals have delayed projects in the past.

"We will call TxDOT on behalf of the developer and the city" when approvals lag, the staff member said, but added that the city has limited authority over state facilities.

The commission also questioned how traffic counts are collected near schools. Staff said on‑site counts must be taken on normal school days (not holidays or summer) and that the city uses both existing counts and ITE estimates—adding proposed trips and a modest annual growth factor—when projecting future conditions.

City staff told commissioners they could request funding during the budget process for local studies to validate ITE assumptions (tube counts or week‑long 24/7 counts) and asked interested commissioners to submit specific use cases within roughly 30 days so the planning department could scope any work and request money from council.

On enforcement, the city engineer's office said it tracks approved TIAs and development lot counts to ensure required mitigations are installed at the agreed milestones, though some older agreements (PIAs) may have different timing provisions.

The training concluded with staff offering to follow up on outstanding questions, supply relevant PIAs as packet resources and coordinate with TxDOT where state roadwork affects local intersections. Commissioners said they would provide follow‑up questions and consider asking for targeted local studies through the budget process.