• Collision warning notifies driver of potential hazard
  • Collision avoidance automatically brakes vehicle
  • IIHS ranks models based on available systems

Collision warning and collision avoidance systems are relatively new, but the advanced safety systems that fall under the broader category of driver assistance are becoming widely available. In fact, it took just a few years for these systems to move from pricey luxury brands into more mainstream vehicles. Now, even affordable models are offered with the technology, although buyers usually have to pay extra to add it as an option.

The Insurance Institute for Highway Safety (IIHS), an independent safety review group that provides crash-test ratings for vehicles, introduced a rating system for frontal collision warning and collision avoidance systems. The new ratings classify the systems as Basic, Advanced or Superior, depending on which features they include and how well they function.

To understand the rankings, it's important to first understand how frontal collision warning and avoidance systems work. Both prevent a vehicle from striking a slower or stopped vehicle ahead. Collision warning systems alert the driver with an audible, visual or other signal when the vehicle is quickly approaching an obstacle. The driver can react by applying brakes or steering around the obstacle. Collision avoidance systems take it one step further, automatically applying brakes if the driver fails to react quickly.

To be considered in the new IIHS ratings, a collision warning or avoidance system must be endorsed by the National Highway Traffic Safety Administration (NHTSA), the federal agency charged with crash-testing vehicles and providing safety ratings. That endorsement is given only for systems that pass an NHTSA test.

Just passing the NHTSA criterion is enough to earn the Basic rating from IIHS. To earn an Advanced rating, the system must also be capable of braking automatically. In other words, only vehicles with crash warning as well as crash avoidance can earn one of the top two ratings. Also, the vehicle must be able to avoid a collision or reduce speed by 5 miles per hour in one of two tests, performed at 12 mph and at 25 mph. To earn the top ranking of Superior, the vehicle must avoid the collision or "substantially reduce speeds" in both tests.

In its first round of testing, IIHS rated 74 2013 and 2014 model-year midsize cars and SUVs and identified 7 that, when equipped with collision avoidance technology, received the Superior rating. The top-ranked vehicles included models from four brands and included the Cadillac ATS and SRX, Mercedes-Benz C-Class, Subaru Legacy and Outback and the Volvo S60 and XC60. Eight other vehicles earned the Advanced rating, and 25 received the Basic rating.

None of the vehicles with systems rated as Superior include collision avoidance as standard features. In fact, the equipment is an extra-cost option on all but two of the models that earned either a Superior or Advanced rating. At least for now, drivers who want the peace of mind of collision warning or avoidance will have to pay extra for the technology.

What it means to you: Collision warning and avoidance can help a driver to avoid a front-end crash, but not all systems are equally effective. Find the full rankings at iihs.org.

author photo

Nick Palermo is an automotive writer and lifelong car nut. He follows new and late-model used vehicles for AutoTrader.com, writes about vintage cars for Hemmings Classic Wheels and blogs on all things automotive at LivingVroom. He lives in Atlanta with his wife and twins.

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