Adaptive cruise control continually adjusts the vehicle's speed to maintain a set minimum following distance. Drivers report that systems that accelerate, decelerate, and steer smoothly improve the experience. IIHS research shows that driver acceptance of lane centering and adaptive cruise control systems can vary considerably by vehicle.

In this feature, sensors monitor the side of the vehicle and alert the driver when other vehicles approach blind spots. In many systems, a visual alert appears on or near the side mirrors when a vehicle is detected. An audible alert may activate if a vehicle is in the blind spot when the driver signals a turn or lane change. Some systems also activate brake or steering controls to keep the vehicle in its lane.

Research demonstrates blind spot detection reduces lane-change crashes by 14 percent.

Some vehicles are available with curve-adaptive headlights, which make it easier to see on dark, curved roads. These headlights pivot in the direction of travel to illuminate the road ahead. The headlights pivot based on steering wheel movement and sometimes the vehicle's speed.

An HLDI study of adaptive headlights offered on Acura, Mazda, Mercedes, and Volvo models showed they lowered property damage liability claims by as much as 10 percent. HID headlights, adaptive high-beam assist, and night view technology provide added safety.

Front crash prevention systems use sensors, like cameras, radar, or light detection and ranging (LIDAR), to detect when the vehicle is getting too close to one in front of it. The systems issue a warning and pre-charge the brakes to maximize their effect if the driver brakes. If the driver doesn't respond, most also automatically brake the vehicle.

Some front crash prevention systems recognize pedestrians, cyclists, and animals. These systems use advanced algorithms coupled with sensors and cameras to spot non-motorists who are in or about to enter the vehicle's path. Front crash prevention is becoming more universal, with more consistent capabilities across brands.

Twenty automakers voluntarily committed to standardizing the technology by 2020. This represents 99 percent light vehicle sales in the United States.

• Forward collision warning (FCW) reduces front-to-rear crashes by 27 percent.
• FCW reduces front-to-rear crashes by 50 percent when combined with autobrake.

These systems use cameras to track the vehicle's lane position, alerting the driver if the vehicle is in danger of straying across lane markings without the turn signal being activated.

Some systems use haptic warnings, such as steering wheel or seat vibration, while others use audible and/or visual warnings. Other systems cause the vehicle to actively resist moving out of the lane or help direct the vehicle back into the lane through light braking or minor steering adjustments.

Lane departure warning systems reduce single-vehicle, sideswipe, and head-on crashes by 11 percent and injurious crashes by 21 percent.

Many different technologies help drivers back up safely. Rearview cameras display what is behind the vehicle, projecting a much larger field than is visible in mirrors or by looking directly out the back windshield.

To reduce back-over crashes, in which victims are frequently young children, new vehicles must have rearview cameras. Some systems warn the driver if objects are in the way when the vehicle is in reverse. Systems with rear automatic braking automatically apply the brakes to keep the vehicle from backing into or over an object.

Rear cross-traffic alert systems detect approaching vehicles that may cross the path of a backing vehicle, warn the driver, and may automatically brake to prevent a collision.

• Rearview cameras reduce backing crashes by 17 percent.
• Rear automatic braking systems reduce backing crashes by 78 percent when combined with rearview camera and parking sensors.
• Rear cross-traffic alert reduces backing crashes by 22 percent.

Connected technology enables communication between vehicles (vehicle-to-vehicle [V2V]) and roadway infrastructure (vehicle-to-infrastructure [V2I]) using a wireless network. V2V and V2I are prototype safety systems.

With V2V communication, vehicles transmit information to other vehicles. If the lead vehicle in a long chain suddenly brakes, V2V systems transmit to other vehicles in the chain and alert other drivers. Trailing vehicles could potentially begin braking automatically when they receive the V2V signal.

With V2I communication, vehicles communicate with roadway infrastructure. For example, highway systems could detect a vehicle’s location within a lane and alert the vehicle if it drifts. In urban environments, traffic signals could alert vehicles of a change so drivers are prepared to stop.

*V2V information from National Highway Traffic Safety Administration

*NHTSA estimates that two V2V functions, intersection movement assist and left turn assist together could prevent nearly 600,000 crashes and around 1,300 fatalities annually when fully deployed across the light vehicle fleet.