Course corrections can be gradual or abrupt. For example, you might observe a vehicle to swerve, making an abrupt turn away from a generally straight course, when a driver realizes that he or she has drifted out of proper lane position, or to avoid a previously-unnoticed hazard.

A related DWI cue is almost striking a vehicle or other object. You might observe a vehicle, either at slow speeds or moving with traffic, to pass unusually close to a sign, barrier, building, or other object. This cue also includes almost striking another vehicle, either moving or parked, and causing another vehicle to maneuver to avoid a collision.

Turning with a wide radius, or drifting during a curve, is the final cue in this category of driver behaviors. A vehicle appears to drift to the outside of the lane, or into another lane, through the curve or while turning a corner. Watch for this cue and stop the driver when you see it. Many alcohol-involved crashes are caused by an expanding turn radius, or drifting out of lane position during a curve.