Gap Judgment and Acceptance

What gap judgment and gap acceptance mean

A gap is the time or distance between a driver and an approaching vehicle. Gap judgment is the driver's estimate of whether that gap is long enough to complete a maneuver, such as a left turn across oncoming traffic, a crossing, or a pull-out from a side street or driveway. Gap acceptance is the decision to go.

Driving research has measured the gaps that drivers typically accept and reject for different maneuvers, and how those choices vary with the speed of approaching traffic, the distance to be crossed, the time a driver has spent waiting, and the driver's age and experience. That research offers a way to compare one driver's decision with what drivers generally do in similar circumstances.

How it bears on driving

To judge a gap, a driver has to detect the approaching vehicle, then estimate how far away it is and how fast it is coming. Distance is the easier of the two. Approach speed is judged largely from looming, which gives little information at long range, so a vehicle traveling faster than a driver expects can arrive sooner than its distance suggests.

Research has found that drivers tend to judge small or narrow vehicles, such as motorcycles, as arriving later than larger vehicles at the same distance and speed. Darkness, sight obstructions and the curve or grade of the road can also limit what a driver has to go on. The analysis considers the other side of the encounter as well: when the approaching driver could recognize that the turning vehicle would enter the path, and respond.

Questions a gap acceptance expert witness can address

• Could the turning driver see the approaching vehicle, and for how long, before starting the maneuver?
• Was the gap one that drivers in similar circumstances would typically accept or reject?
• Did the approaching vehicle's speed, size or lighting make its approach harder to judge?

This article is general information, not legal advice or an expert opinion on any matter. See the disclaimer.