Time, distance & velocity
Perception-Reaction Distance Calculator
Calculate how far a vehicle travels during a supported perception-reaction interval at a given speed.
Relationship
distance = velocity × time
feet = mph × 1.4667 × seconds
feet = mph × 1.4667 × seconds
The arithmetic is simple; selecting and supporting the time interval is the substantive part of the analysis.
Questions to document
- When the hazard or cue became available and detectable.
- What response was reasonably available to the driver.
- Which study or case-specific evidence supports the selected time.
- Whether speed remained constant during the interval.
A highway-design value includes a design safety margin and should not automatically be substituted for a case-specific driver response value.
Related tools
Total stopping distance · AASHTO stopping sight distance · Time-space diagram