AAA thinks that rear cross-traffic alert systems are more or less bunk
Many systems that the group tested failed to recognize objects that could cause a collision, including motorcycles and pedestrians.
RCTA systems have plenty of limitations, nearly all of which are related to line of sight. As you can see in this picture, it's more or less useless in a thick line of diagonal parking spaces.
The American Automobile Association (AAA) takes driving quite seriously. After lambasting automakers for removing spare tires and replacing them with inflator kits, the advocacy group is once again on the offensive. This time, it's taking aim at rear cross-traffic alert (RCTA) systems, claiming that the system comes with plenty of limitations.
RCTA works using sensors. When the car is reversing, these sensors look for changes on either side of the car -- say, if a vehicle is approaching. When the system catches wind of something moving towards the car, be it a pedestrian, a car or something else, it will alert the driver, ideally preventing a collision.
The system isn't perfect, though. If you're stuck between two large cars, the sensors cannot read "through" those vehicles, rendering RCTA moot. If other cars are parked incorrectly -- say, hanging out of a space -- that can affect its efficacy, as well.
Without saying which systems it tested, AAA uncovered a surprisingly high failure rate. Motorcycles were missed 48 percent of the time, 40 percent of bicycles were never detected, and 30 percent of passing vehicles were also not recognized. RCTA also failed to detect pedestrians 60 percent of the time, but not every automaker claims that its system can do that to begin with.
While RCTA may be effective if you have clear sight lines, there is no proper replacement for a set of functioning eyeballs and keen spatial awareness. "It's critical that drivers reverse slowly and use this technology as an aid to, not a substitute for, safe driving," said Megan McKernan, manager of the Automobile Club of Southern California's research center.
Or, you could do as AAA says in its release and back into perpendicular parking spots. Then, when it's time to leave, all you have to do is roll forward slowly, ignoring backup cameras and sensors and all that.