Traffic Impact Assessment - Examples & Applications

Example

An intersection carries 1,250 veh/h1,250\text{ veh/h} in the current PM peak. A development opens in four years. If a screening study assumes 2.0%2.0\% annual compound background growth, estimate the opening-year no-build volume.

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Example

A proposed development is estimated to generate 420420 PM-peak-hour driveway trips. A justified pass-by fraction of 25%25\% applies to the land use. Determine the screening estimate of primary/diverted trips that add demand to the broader network, while also identifying the driveway effect of pass-by trips.

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Example

The 315 trips/h315\text{ trips/h} from the previous example are distributed 55%55\% north, 30%30\% south, and 15%15\% east. Determine the assigned peak-hour demand by approach.

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Example

A signalized approach has a no-build average control delay of 43 s/veh43\text{ s/veh} and a build-condition delay of 67 s/veh67\text{ s/veh}. The 95th-percentile queue also increases beyond the available turn-lane storage. Explain why the mitigation review must consider more than the LOS letter.

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Key Takeaways
  • A TIA separates existing, future no-build, and future build conditions.
  • Background growth and trip-generation adjustments must be justified rather than selected to force an outcome.
  • Pass-by trips may reduce regional added traffic while still affecting site driveways.
  • Mitigation should address delay, queues, storage, safety, multimodal access, and local approval criteria.