Saccades
One quick glance is sometimes not enough: what is happening on the road may change while your gaze shifts.
What is a saccade?
A saccade is a rapid eye movement from one point to another. Some changes are harder to notice during that movement, so a single brief check is sometimes not enough.
Where this matters
- a mirror check before changing lanes
- a side-road entrance
- a turn across oncoming traffic
- a quick intersection check
Things can change between your check and your maneuver
Before changing lanes, crossing another vehicle's path, or pulling out from somewhere with a restricted view, check the hazard area again just before you act.
What to look for
Check both directions on the road you are crossing. Look at cars that could turn in front of you and at gaps between stationary vehicles, where a pedestrian could emerge.
Sources · 1
- Perceptual saccadic suppression starts in the retina
Introduction; Results
Used for: Reduced visual sensitivity during rapid gaze shifts.
Open source
Saccades and perception
Vision does not switch off completely during a saccade, but some changes are harder to notice. We perceive the road as a continuous scene, even though our gaze pauses on individual points and moves quickly between them.
Why you can miss something
An object can appear, accelerate, or shift position while your gaze shifts. One fixation may not be enough to notice that change and assess it correctly.
What changed between glances?
When your maneuver depends on a car's movement, look at it again and compare its position with what you saw before. This makes it easier to notice that it has moved sideways or that the space beside it has shrunk.
The situation may already have changed since your first glance. Before an important maneuver, briefly check the hazard area again.
Make two brief checks before a maneuver
- check the hazard area
- look back at the road ahead
- briefly check the area again just before the maneuver
After checking a mirror
Do not keep looking in the mirror longer than you need to check behind you. The road ahead is still changing.
Keep the second check brief
The second glance lets you see what has changed since the first check. Afterward, look where you are going again.
A common mistake
Looking once, seeing an empty space, and then carrying out the maneuver using an outdated picture of the situation.