Parking crashes usually don't result in serious injuries, but repair costs can quickly mount, along with the hassle of going without the family vehicle while waiting for the body shop to finish work. The Insurance Institute for Highway Safety has launched a rear crash prevention ratings program to help consumers identify models with the technology that can prevent or mitigate low-speed backing crashes.

Two systems earn the highest rating of superior, and four earn the second-highest rating of advanced.Rear crash prevention encompasses several technologies. Parking sensors issue warning beeps and/or seat vibrations when the equipped vehicle gets too close to another vehicle or object directly behind it, or, in some cases, in front of it.

Rear cross-traffic alert warns drivers of approaching vehicles that might cross their path as they back up. Rear automatic emergency braking systems detect objects behind a reversing vehicle and may automatically brake if the driver doesn't heed alerts to stop."Let's face it. Some days we all could use help backing up, whether that's in a garage with pillars that obscure your view, in a crowded mall parking lot or on a busy downtown street," says David Zuby, the Institute's executive vice president and chief research officer.

"The systems we rate in our first batch of tests will help reduce the chances of a backing fender-bender.

"IIHS engineers evaluated rear autobrake systems on six popular 2017 model vehicles — the BMW 5 series sedan, Cadillac XT5 SUV, Infiniti QX60 SUV, Jeep Cherokee SUV, Subaru Outback wagon and Toyota Prius hatchback.

Under the three-tier rating scheme, models with optional or standard rear crash prevention systems are rated superior, advanced or basic. Ratings are determined by whether the vehicles have available rear autobrake and, if so, how it performs in a series of car-to-car and car-to-pole tests with different approach angles. The availability of parking sensors and rear cross-traffic alert also is factored in. The Outback and XT5 earn a superior rating when equipped with optional rear autobrake, parking sensors and rear cross-traffic alert.

The Cherokee, 5 series, QX60 and Prius earn an advanced rating with this optional gear. The ratings evaluate the rear crash prevention systems' ability to prevent damage in low-speed crashes, not their ability to mitigate injuries in crashes.Research from IIHS and the Highway Loss Data Institute (HLDI) indicates that these technologies prevent crashes.

The combination of a rearview camera, rear parking sensors and rear autobrake is reducing backing crashes reported to police by 78 percent, a new IIHS study of General Motors' vehicles found. Rear autobrake systems from GM and Subaru also are reducing the frequency of claims reported to insurers, HLDI reported in August 2017. In the new ratings program, rear autobrake carries the most weight because research shows it provides the biggest crash reductions.

Parking sensors and rear cross-traffic alert get partial credit. HLDI has found benefits for parking sensors in reducing crashes reported to insurers, while new research from IIHS shows that rear cross-traffic alert is reducing police-reported crashes.

For a superior rating, a vehicle must have a rear autobrake system that can avoid a crash or substantially reduce speeds in many of the test scenarios, which involve multiple runs at about 4 mph. Systems are assigned points based on the number of runs that either avoid or barely hit the target, reducing speeds to less than 1 mph.

For advanced, a vehicle must have rear autobrake and avoid a crash or reduce speeds in some of the scenarios. Vehicles that only have parking sensors and/or rear cross-traffic alert earn a basic rating.Rear autobrake isn't as prevalent as front autobrake. The feature is optional on only 5 percent and standard on less than 1 percent of 2018 model passenger vehicles, HLDI estimates. Rear cross-traffic alert is optional on 43 percent and standard on 11 percent of 2018 models. Rear parking sensors are standard on 33 percent and optional on 59 percent of 2018 models. Rearview cameras are standard on 89 percent and optional on 10 percent of 2018 models.Demonstration tests

To illustrate how repair costs can add up, the Institute conducted four low-speed demonstration tests with and without rear autobrake, and then tallied the damage as a claims estimator would. Scenarios included the XT5 backing into a pole and the Outback reversing into a 2016 Chevrolet Cruze.

When equipped with rear autobrake, the vehicles didn't strike anything, so there was no damage. Without autobrake was a different story.The XT5 needed an estimated $3,477 in repairs after backing into a pole. Damaged parts included the bumper cover, tailgate, hitch bar, energy absorber, rear body panel, trim and assorted brackets.When the Outback backed into the Cruze's rear bumper, the estimated damage for both cars came to $1,899 — $1,159 for the Outback and $740 for the Cruze.

How vehicles rate for rear crash prevention, 2017 models

Superior

Cadillac XT5
Subaru Outback

Advanced

BMW 5 series sedan
Infiniti QX60
Jeep Cherokee
Toyota Prius