Four Seconds

Four Seconds: Following Distance and Dispatch Pressure

Hattie’s church van slows with traffic. The truck behind has left little room. Warnings and an ambitious appointment time raise questions beyond the final seconds.

Safe distance depends on conditions

A.R.S. 28-730 requires reasonable and prudent following distance considering speed, traffic, and road conditions. It does not prescribe one four-second rule for every situation.

The ADOT CDL manual provides space-management guidance. Load, surface, speed, and visibility affect needed room. The episode’s title invites examination of the gap, not a universal liability formula.

Check how the system measured the gap

Telematics, video, speed, braking data, and system definitions can test the eight-tenths-of-a-second interval. Confirm it concerns the same vehicle and time as the collision.

Repeated warnings may show notice or training issues. Preserve carrier responses as well as the count. A raw alert needs interpretation before it proves unsafe conduct; false detections and gaps in recordings should not be silently ignored.

Investigate the schedule against the route

Appointment windows and dispatch messages may show whether planning encouraged unsafe driving. Compare with realistic travel time, traffic, and required breaks. Pressure is relevant, but connect the schedule to actual driving and harm. Sudden traffic changes also belong in the reconstruction.

Questions this episode raises

Is four seconds always the legal minimum?

No. Arizona’s rule concerns reasonable distance in context; larger gaps may be needed.

Can earlier alerts matter?

They may show notice and response, but accuracy and relevance must be established.