Advanced Driver-Assistance Systems Explained

Automotive safety systems that can warn or even intercede when things go wrong are not new. Anti-lock braking has been around for decades. So, too, has electronic stability control, which helps control a skid and has proved to be so effective that it is now required on all new cars. With at least 20 years of exposure to these systems, most of us have grown comfortable with ABS and ESC.

Now, however, a new collection of advanced driver-assistance systems (ADAS) has arrived with an entirely new set of potentially bewildering labels. LKAS, LDW, BSW, ACC, RCTA, FCW and FCB are currently found on a wide range of models. What are these systems and are they worthwhile? To help answer these questions, here is a brief description of some of the new advanced driver-assistance systems on the market.

LDW – Lane-departure warning:
This system usually uses cameras to find the lane markings painted on roadways. If the driver starts to drift over one of these lane markings without signaling, the car issues a warning. As good as these systems are, they are not foolproof. Freshly painted temporary lane markings in construction zones may confuse the system. The absence of lines, or a covering of snow, will also disable the system. Still, the Insurance Institute for Highway Safety believes LDW could prevent many serious crashes.

LKAS – Lane-keep Assist System:
Imagine a lane-departure warning system that doesn’t just warn a drifting driver but actually tries to steer the car back into its lane. Some of these systems are so good that they will actually guide a car through a turn, as long as there are lane markings. Most of these systems now shut down if they sense the driver has removed his or her hands from the steering wheel for more than 20 seconds. Nonetheless, a car that can help keep a distracted driver from drifting off the road has obvious safety benefits.

ACC – Active Cruise Control:
Once engaged, ACC slows the car automatically to maintain a set following distance when encountering a slower-moving vehicle. If a driver has set the cruise control to 65 mph and then catches up to a car traveling at 55 miles per hour, this system will automatically reduce the speed with no driver involvement. In many models, ACC will apply the brakes automatically if that is required. Some systems will bring the car to a stop if the car ahead stops.

BSW with RCTA or Blind-spot Warning with Rear Cross-traffic Alert:
This system warns when another driver is lurking in the next lane in the driver’s blind spot. Some systems will also warn of a car approaching quickly on the open road from the rear. In parking lots, RCTA warns of a car coming from either side when backing out of a parking space. This can be very handy when parked next to a vehicle that blocks your view, such as a large panel van.

FCW and FCB – Forward Collision Warning and Forward Collision Braking:
These systems compute the probability of a forward collision and warn the driver. If the driver does not respond, cars with FCB will apply the brakes to either prevent or mitigate the crash. Research shows that systems that can apply the brakes reduce rear-end crashes by about 40 percent. Those that simply warn the driver have delivered a 23 percent rear-end crash reduction, according to IIHS research. Its website,, shows which cars have the systems that work best.

Other relatively new safety systems include adaptive headlights that adjust in response to steering inputs; night vision assist, which can help drivers pick out hazards, including pedestrians, when driving at night; and rear automatic braking, which can prevent hitting an object or person behind the vehicle when backing.

As good as advanced driver-assistance systems are, however, they don’t replace the driver. It’s best to think of these advanced systems as a safety net, not the primary means for vehicle control. Even the best of these systems is no match for an engaged and capable driver.

James MacPherson is a freelance automotive writer and broadcaster from South Windsor, Conn.

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