A blind-spot warning (BSW) system can reduce both stress and the risk of a crash by helping you keep tabs on vehicles over your shoulder and out of sight. Until recently, the only way to get one was to invest in a new car.

Never to miss an opportunity, the ever-vigilant automotive aftermarket has risen to the need, and a handful of systems are now available to update almost any vehicle with the technology.

The Goshers Blind Spot Detection system was chosen to test. It includes a sensor for each side of the rear bumper, a left and right side LED warning display, an audible alarm unit, a controller, and all the necessary wiring to link the whole thing together.

The company website stresses that professional installation is required, but it does not provide a list of installers or a cost estimate to do the job.

Installation is somewhat complicated. It requires splicing into the car’s wiring, holes in the rear bumper for the sensors, and removing and reinstalling various interior trim pieces to route the wires and keep them out of sight.

Local repair garages should be able to perform the installation, but get an estimate first if you decide to buy the kit. A certified automotive technicians needs about four hours to install the system in a typical car.

Overall, the Goshers system works as advertised; it consistently warns of other cars in the blind spots with both an audible and visual warning. If anything, the system was a little overzealous, at least until adjusting the sensitivity level to its lowest setting and opting to receive warnings only when a turn signal was switched on. Without making those adjustments, warnings are almost constant, as the system warns of guardrails, roadside walls, tunnels, and other large objects.

What cannot be changed is that unlike a built-in system that typically deactivates below a certain speed threshold, the Gosher system operates at any speed, and there is no on/off switch other than sound.