N ot so long ago, it would have seemed incredible that your car would be able to “see” other vehicles or pedestrians, anticipate collisions, and automatically apply the brakes or take corrective steering actions. But more and more cars can do that to some degree, thanks to a growing list of collision-avoidance systems.

Some of these capabilities, such as forward-collision warning systems, have been around for a few years, mostly on high-end luxury cars. Others, like steering assist, are just getting ready for prime time. The good news is that the collision-avoidance systems are getting better and are spreading to mainstream cars.

The potential for these systems is so great that the Insurance Institute for Highway Safety has added collision-avoidance system testing to its suite of safety evaluations. The IIHS has determined that some of these collision-avoidance systems could prevent or mitigate many crashes. Now, to win top overall safety scores from the IIHS, a car needs to have a forward-collision warning system with automatic braking. In addition, any autobrake system has to function effectively in formal track tests that the IIHS conducts. Visit IIHS website for test results on individual models.

The federal National Highway Traffic Safety Administration is also on board, with an eye to making some collision-avoidance systems mandatory. NHTSA’s 5-Star Safety Ratings note which systems are available on cars they crash-test. Their presence doesn’t affect the Star ratings yet, though.

The cost of collision-avoidance systems can still be an obstacle. Most advanced systems today come only as part of a large options package or on a model’s higher, more expensive trim versions. Jumping to the trim line where the safety goodies are offered can add thousands of dollars to a vehicle’s price. 

Lasers, Radar, and Cameras

These cutting-edge active safety systems rely on a number of sensors, cameras, lasers, and short- and long-range radar. They monitor what is going on around the vehicle—vehicles, pedestrians, cyclists, and even road signs—as well as the vehicle itself. Inputs are processed by computers, which then prompt some action from the car or the driver. Those actions may start with attention-grabbers, such as a beep, a flashing dashboard icon, a tug from the seatbelt, or a vibration in the seat or steering wheel. If the driver doesn’t respond, the more advanced systems then apply partial or full braking force.

In our ongoing evaluations we’ve found that there’s a fine line between a helpful electronic co-pilot and a computerized backseat driver. If a warning system emits too many inappropriate alerts, then there is an increasing temptation to switch it off.

Not every system on the market today is top-notch. The IIHS has found that some autonomous braking systems are more effective than others. But they conclude there’s a net benefit regardless.

A 2009 study conducted by the IIHS found a 7 percent reduction in crashes for vehicles with a basic forward-collision warning system, and a 14 to 15 percent reduction for those with automatic braking.

“Even in the cases where these systems failed to prevent a crash, if there’s automatic braking going on, or if the driver does brake in response to a warning, that crash is going to be less severe than it would have been otherwise,” says David Zuby, chief research officer at the IIHS.

In the end, these systems can do a lot of good in preventing crashes from happening in the first place. But it’s important for drivers to realize that none of these aids reduces the need to stay alert.

Current Active Safety Systems

Manufacturers routinely use unique, marketing-friendly names for their various systems. This makes it confusing to know the system’s full capabilities. When you are shopping for a new car, make sure to ask what the safety feature does. For a detailed listing of the available systems for each manufacturer, visit our free Car Safety Hub.

Rear cross-traffic alert
Cross-traffic alert warns you of traffic approaching from the sides as you reverse. The warning usually consists of an audible chirp and a visual cue in either the outside mirror or the rear camera’s dash display. The more advanced systems can also pick out bicycles and pedestrians.
CR’s take: Cross-traffic alert systems are especially handy if you have to back into a traffic lane when adjacent parked cars obscure your view.

An illustration of how collision-avoidance systems worl

Forward-collision warning (FCW) and autobrake
Also called a pre-crash warning system, these stand-alone or combined radar-, laser-, or camera-based systems warn drivers of an impending collision by using visual, auditory, or physical cues. Most vehicle systems also pre-charge the brakes and take other steps to prepare for impact. If the driver ignores the warnings, systems with autonomous braking, or autobrake, will apply partial or full braking force. They can be active at anywhere from walking to highway speeds.
CR’s take: Sometimes you want or need to stay closer to the car ahead of you than at other times, so systems that let you adjust your follow distance have a distinct advantage.

Blind Spot Alert

Blind-spot monitoring (BSM) and assist
A blind-spot monitoring system uses radars or cameras to scan the areas beside and behind you, looking for vehicles entering or lurking in your blind zones. When such a vehicle is detected, an illuminated icon appears in or near the appropriate side-view mirror. If you signal a turn while a car is in your blind zone, some systems send a stronger alert, such as a blinking light or louder chirps. More advanced systems help keep you in your own lane by applying the brakes on one side of the vehicle.
CR’s take: In general, we like these systems and find them helpful.

Pedestrian detection and braking
Pioneered by Volvo and now offered by others, pedestrian detection can recognize a person straying into a vehicle’s path. Some will automatically apply the brakes, if needed, sometimes partially and sometimes to a complete stop. Some newer systems can also detect bicyclists.
CR’s take: They’re a good investment, especially if you often drive in cities or other populous areas.

Adaptive headlights
As you turn the steering wheel adaptive headlights will swivel, which helps illuminate the road when going around curves. A 2014 IIHS study found that adaptive headlights improved drivers’ reaction times by about a third of a second. That could be just enough to avoid, say, hitting a parked car on a dark road.
CR’s take:
Our drivers have mixed feelings about adaptive headlights. The wider view can be helpful, but the swiveling motion of the light path can be a little distracting, especially if the headlight beams’ motion isn’t exactly synchronized with the steering wheel’s.

Subaru EyeSight Cameras

Lane departure warning (LDW) and assist LDW
These systems use a camera, along with various sensors, to identify lane markers and monitor your distance from them. If you stray over the line without signaling, you’ll hear a warning tone or perhaps a physical alert like a vibration in the steering wheel or seat. More advanced “lane keeping assist” (LKA) systems selectively apply brakes or nudge the steering to guide you back if you’re wandering.
CR’s take:
We’ve found LDW more useful on highways than on narrow, winding country roads where they can beep at you too often. We also prefer systems that make corrections using the steering rather than the brakes.

Drowsiness detection
Various methods are used to detect if a driver is tired or falling asleep. Mercedes-Benz pioneered one of the first, which uses a computer algorithm that compares a driver’s steering behavior with those recorded at the start of the trip. Other systems monitor the car’s position within its lane of travel, looking for erratic maneuvers indicative of inattention. Some also track the driver’s eye movements with an in-car camera, noting rapid or prolonged eye blinks. Alerts may include a chime, a dab on the brakes, a tug on the shoulder belt, and/or an illuminated cup-of-coffee icon on the instrument panel.
CR’s take:
Anything that keeps a driver from falling asleep is probably a good idea. We haven’t experienced any problems, such as false alarms, on cars we’ve tested with the feature. In addition to drowsy-driving, these systems can tell you to look sharp if you’re wandering around in your lane. Some may even keep drivers from looking down to text or answer emails.

Automatic park assist
The system will identify a parallel or perpendicular parking space your car can fit into. Once found, the system steers the car into the space; some can also exit from parallel parking spaces. The driver still does the braking and has to follow commands from the system.
CR’s take: These can be awkward to initialize. The driver has to activate the system and then drive by an open space for the system to recognize the spot. It may not recognize the parking space the first time. But most do a good job at steering the car into the spot.

Rear cameras and parking assist
Rear-view cameras will be mandatory with the 2018 model year. They can help prevent a back-over accident, such as hitting a child who wanders behind your car. Parking assist sensor systems notify you with progressively louder and quicker beeps as you close in on an obstacle.
CR’s take: These are a must-have on SUVs and pickups, which often have large blind zones behind them. In addition, rear cameras are great when backing into tight parking spaces or lining up a trailer.