Hear "left turn assistant" and you might think stereotypical images of helping drivers of a certain German marque to use their blinkers for once when turning, but you'd be quite wide of the mark...
BMW's Left Turn Assistant is actually a safety system designed to help drivers turning left across intersections. At larger intersections with traffic approaching from the other direction, drivers can occasionally make a bad call and begin their maneuver without the time to do so, and sometimes traffic signal poles can obscure smaller road users such as motorcycles.
The BMW system helps prevent collisions with oncoming traffic. Using a combination of sensors, a mono camera and the car's navigation system to pinpoint its location, the car knows when a driver is entering the left-turn lane. Three laser scanners then monitor the road ahead up to 100 meters (328 feet) in front, and if they detect the driver turning even though traffic is approaching, the car can automatically brake to prevent an accident.
To ensure adequate accident prevention, the car will only automatically brake below 6.2mph (or 10km/h in metric Europe). At any quicker speeds one danger would only be swapped for another as your car would more likely end up stranded in the way of the oncoming traffic.
For the same reason, the system offers no warning prior to taking action. If traffic is approaching then issuing a warning before braking would mean the difference between stopping short of oncoming cars or stopping directly in their path.
The system can also be overridden for occasions where moving forward is necessary, such as moving out of the path of an emergency vehicle attempting to pass. All the driver needs to do in this situation is dab the gas pedal.
BMW says the system can also be combined with more sophisticated vehicle detection systems such as car-to-car communication as trialled by companies like Ford. If the car approaching is equipped with the technology, the "visible range" is extended to 250 meters (820 feet).
It'll even work with motorcycles equipped with the technology, and BMW are testing using a 5-Series and a R1200 GS motorcycle. In such a scenario, the bike can adjust its headlamp beam to become more visible to the driver wishing to turn left.
There's no word on when the tech will be available in BMW's cars just yet, but the company will be premiering the system at a safety meeting, INTERSAFE 2, in Wolfsburg, Germany in May.