Traffic is emotional for residents. For engineers, it is data. The Traffic Impact Study (TIS) is the document that bridges that gap.
Trip Generation (ITE Manual)
We don't guess how many cars a Starbucks generates. We look it up in the Institute of Transportation Engineers (ITE) Trip Generation Manual. This bible of traffic engineering tells us exactly how many trips to expect during the AM and PM peak hours based on the square footage and use type.
Level of Service (LOS)
Intersections are graded like a report card, from A (free flow) to F (gridlock). The goal of the TIS is to prove that your development will not degrade the LOS below an acceptable level (usually C or D).
Mitigation
If your project does degrade the LOS, you have to fix it. This is "mitigation." Common measures include:
- Adding a turning lane.
- Retiming traffic signals.
- Restriping the intersection.
- Contributing to an off-site improvement fund.
County & State Roads
If your project fronts on a County road or a State Highway (DOT), the local board doesn't have the final say. You need a separate approval (and often a separate access permit) from the County Planning Board or NJDOT. Their standards are often much stricter than the municipality's.
Conclusion
You can't hide the cars, but you can manage them. A good traffic engineer is worth their weight in gold during public testimony.