Blind-spot monitoring (BSM) is an active driver aid/safety device with the ability to detect what your eyes may miss, issuing a warning as a vehicle approaches from behind in an adjoining lane.
These sensors employ radar and/or cameras to spot encroaching or lingering traffic. When these sensors detect vehicles in your blind spots, they alert the driver with visual notifications in the outboard mirrors, like lights or icons; the signals may warn the driver with audible alerts also.
While a blind-spot monitor is an increasingly common active-safety feature, new-car buyers may have to purchase models at higher trim levels or with specific options to gain it. For owners of cars without a blind-spot monitor, aftermarket systems are available should they want to add the technology.
