California
Traffic Impact Study
A traffic engineer estimates trips from your project and their effect on nearby roads, as required for many approvals.
What the work involves
A traffic impact study (TIS or TIA) estimates trips a development will generate, commonly using ITE Trip Generation data, counts existing traffic, analyzes intersection level of service and queues, and recommends turn lanes, signals or other mitigation. Local codes usually set a trip threshold that triggers a study. The study is prepared by a professional engineer experienced in traffic engineering.
Local conditions we plan for
- High seismic hazard and active faults
- Wildfire in the wildland urban interface
- Landslides and debris flows on steep slopes
- Coastal bluff erosion and sea level rise
Building code: California Building Standards Code (Title 24), based on the 2024 IBC and IRC, statewide (ICC adoption chart, April 2026).
When you need it
- Development exceeds the local peak hour trip threshold
- New access onto a state highway
- Rezoning or special use permit with traffic concerns
- Agency requests mitigation analysis
Frequently asked questions
How much does traffic Impact Study cost?
Across the US, traffic Impact Study usually costs $5,000 to $100,000 per study. City of Pleasanton staff reports describe a range of $5,000 to $100,000 with most around $30,000; an industry source cites roughly $10,000 to $30,000 for typical development studies. Simple trip generation letters cost less.
How long does traffic Impact Study take?
Plan on 3 to 10 weeks, depending on count timing and agency review from signed proposal to stamped deliverables, longer if a site visit, soil testing or a permit review cycle is involved.
Do I need a licensed PE for traffic Impact Study?
In most US jurisdictions, yes. When the work needs a permit, the plans, calculations or report usually must be sealed by a Professional Engineer licensed in the state where the project is located. Every deliverable we issue for permit is sealed that way.
How do I verify an engineer's license in California?
Engineers practicing in California are licensed by the Board for Professional Engineers, Land Surveyors, and Geologists (BPELSG). You can confirm a license number and its status in the board's public license search before you sign a contract.
Which building code applies in California?
California Building Standards Code (Title 24), based on the 2024 IBC and IRC, statewide (ICC adoption chart, April 2026). Cities and counties can add local amendments, which is one reason to hire an engineer who works in your area.
What site problems do engineers see most in California?
Common issues include high seismic hazard and active faults, wildfire in the wildland urban interface, landslides and debris flows on steep slopes and coastal bluff erosion and sea level rise.