Performance Mixed for Blind Spot, Lane Departure Systems

AAA cautions drivers that blind spot detection and lane departure warning systems may not work as expected under varying road conditions and from one model to another.

The two technologies are now available in more than half the new models offered in the U.S. AAA says both features are a great asset, but it notes each one comes with its own learning curve for users. Lane departure systems, for example, can lose track of where the lane is in construction zones or intersections.

It adds that blind spot warning systems may ignore motorcyclists or have trouble spotting other cars that are moving significantly faster or slower. Sometimes such systems fail to issue an alert until an object is already in the blind spot's collision zone.

Neither safety system activates until the vehicle reaches a threshold speed that varies among manufacturers. Some blind-spot systems don't work when the vehicle is in reverse. Owners' manuals reveal that some systems are designed to function effectively only on the highway. Others may not detect such objects as people, animals or bicyclists.

Both systems are prone to false-positive and missed detections. AAA points out that false warnings could make drivers tune out a system or switch it off. AAA's advice to drivers: Review each feature and be aware of its limits.