A driver is much less likely to be involved in a rear-end collision if their vehicle is equipped with front crash prevention, a study by the Insurance Institute for Highway Safety recently concluded.

IIHS analyzed police-reported rear-end collisions for its latest study on the effectiveness of front crash prevention. Researchers concluded that systems that brake automatically led to a 40 percent reduction in rear-end collisions on average, along with a significant reduction in injuries. Systems that only warned a driver of an impending collision with a vehicle in front of them still resulted in a 23 percent reduction in this type of accident.

The study concluded that 700,000 rear-end collisions reported to the police in 2013 and 300,000 associated injuries could have been avoided if the vehicles involved had automatic braking that worked as well as the systems included in the study. This reduction would have cut down on police-reported accidents by 13 percent.

"The success of front crash prevention represents a big step toward safer roads," said David Zuby, IIHS chief research officer. "As this technology becomes more widespread, we can expect to see noticeably fewer rear-end crashes. The same goes for the whiplash injuries that often result from these crashes and can cause a lot of pain and lost productivity."

Researchers analyzed rear-end collisions reported to police in 22 states. The study compared the crash rates of Acura, Honda, Mercedes-Benz, Subaru, and Volvo vehicles with model years between 2010 and 2014. Each of these vehicles had front crash prevention as an optional feature, and crash rates of vehicles equipped with the feature were compared to the same model that did not have the feature.

IIHS also conducted a separate analysis of City Brake, a standard Volvo system which brakes automatically if it senses a collision when a vehicle is moving at speeds up to 19 miles per hour. This study included 27 states and compared the frequency of rear-end collisions on S60 and XC60 models equipped with City Safety with other midsize luxury SUVs that did not have front crash prevention.

The studies only included incidents where a driver ran into a vehicle in front of them, not collisions where a vehicle equipped with the technology was rear-ended. Researchers also controlled for factors that may have affected crash rates, including the vehicle's location and driver characteristics.

Researchers concluded that forward collision warning systems reduced rear-end collision rates by 23 percent. When the system was paired with automatic braking, the crash rate dropped by 39 percent.

Automatic braking systems were also effective in reducing the likelihood of injury in a rear-end collision. These systems cut down on rear-end collisions with injuries by 42 percent. The reduction in rear-end collisions with injuries was not statistically significant when the system only issued a warning, with crash rates dropping 6 percent for incidents with injuries.

Vehicles with the City Safety system had 41 percent fewer rear-end collisions than comparable models without front crash prevention. The system also resulted in a 47 percent reduction in rear-end collisions with injuries.

"Even when a crash isn't avoided, systems that have autobrake have a good chance of preventing injuries by reducing the impact speed," said Jessica Cicchino, IIHS vice president for research and author of the studies. "Still, it's surprising that forward collision warning didn't show more of an injury benefit, given that HLDI has found big reductions in injury claims with the feature."

A previous study by the Highway Loss Data Institute, published in August 2015, found that front crash prevention systems resulted in a decline in insurance claims. That research looked at three different models equipped with the technology and found that they reduced claims by 12 to 39 percent.

While the City Safety system is designed to prevent collisions at lower speeds, it was most effective on roads with speed limits of 40 to 45 miles per hour. Compared to comparable models, Volvo models with the system were 54 percent less likely to collide with the back of other vehicles at this speed. Rear-end crash frequency also dropped 39 percent on roads with a speed limit of 35 miles per hour or less and 25 percent on roads with a speed limit of 50 miles per hour of higher.

"At first blush it's surprising that this low-speed system was most effective on 40-45 mph roads," said Cicchino. "However, these roads tend to have many traffic lights, which reduce actual travel speeds in places. In addition, City Safety can come into play whenever there is congestion on a higher-speed road."

IIHS noted that one difficulty in the study is isolating the effect of front crash prevention, since the system is typically offered alongside a number of other collision avoidance technologies. These include adaptive cruise control and lane departure warning.

Researchers said some of the reduction in rear-end collisions may have been a result of adaptive cruise control, which uses sensors to maintain a safe following distance behind another vehicle. However, drivers usually have to activate adaptive cruise control, while front crash prevention is always active. The studies also concluded that lane departure warnings have little effect on the frequency of rear-end crashes.

Currently, front crash prevention is optional rather than standard on most models. The technology has become more common, however, and is more likely to be standard equipment in the near future. In September, IIHS and the National Highway Traffic Safety Administration announced an agreement with 10 automakers to make automatic emergency braking a standard feature on their models.