Driverless cars haven’t hit the roads yet, but computers are already helping to slow down or stop a car in situations when a crash is imminent. Still, just like people, these systems require time to react. Using sensor technology already in its vehicles today, Toyota is aiming to reduce the impact of accidents happening at faster speeds.

A number of carmakers today use autonomous braking technology as a safety feature, and recent work by the Highway Loss Data Institute shows that they can have a measurable safety effect as shown in insurance claims. One key challenge for carmakers is how to introduce safety technologies without letting drivers become too dependent on their computer-controlled cars (see “Proceed With Caution to the Driverless Car”).

Toyota introduced its first system that can brake a car on its own last fall, starting in its 2013 Lexus LS, the highest-end Lexus model. Lexus’s “pre-collision” systems already used millimeter-wave radar behind the front grill to detect when a vehicle approaches dangerously close to a car ahead of it, based on the relative speeds of the two cars. Previous models of Lexus would alert the driver, tighten the seatbelt, and prepare to apply the brakes so the car could be slowed more quickly and safely if and when the driver engaged them.

The brand’s newer systems can slow the car even if a foot never hits the pedal, decelerating enough to avoid collision at relative speeds below 25 miles per hour (the speed between a driver’s car and the car ahead). It also uses stereo cameras to detect pedestrians and infrared to see nighttime obstacles.

Much of the advantage is due to software improvements that make the decisions to activate and control the brakes. “The millimeter wave radar sensor can only see out so far. So the question is: at the time we can detect it, what’s the rate we can slow it down?” says Bill Camp, an instructor at the company’s training facility, Lexus College.

A future generation of Toyota’s pre-collision system will be able to work at higher speeds, and will decelerate a car by up to 37 miles per hour to reduce the impact of a collision, the company says. Achieving that number will still require a person to apply the brake, but the company says that more than 90 percent of rear-end collisions happen when the speed difference between two cars is within 37 miles per hour, and it plans to introduce the system soon for a “wide variety of models.”

Today, Google’s driverless cars are already being tested on California roads, and so technology exists that could avoid crashes in many more scenarios. But it is extremely expensive. Lexus showed off its own driverless research car with a similar laser system on top at the Consumer Electronics Show this year; the laser system costs in the range of $75,000, Camp says (“Toyota Unveils an Autonomous Car, But Says It’ll Keep Drivers in Control”). The company hopes this vehicle can be a test-bed for improving its product lines today.

Costs are already starting to drop for using more standard sensor-based safety technologies, and that will be important for introducing them into cars that don’t cost as much as a Lexus. For example, in the 2013 model year, 29 percent of cars had an optional forward-collision warning system, and of these, 12 percent had autonomous breaking, according to the Highway Loss Data Institute.

Software that allows the same sensors to perform dual functions can help. Lexus, for example, now uses the same light sensor to direct both automatic high beams and a lane departure alert system, whereas these functions used to require two sensors.

When the brand first began using millimeter wave radar collision warning systems in cars almost a decade ago, it was a $2,500 option for its flagship brand, Camp says. With refined electronics, it now is a $500 option in Lexus’s slightly lower-end IS line this year, a price that also includes a dynamic cruise control feature that can use the same radar.

“This is the first one that’s $500,” says Camp. “So if they keep going that route, you might just see it on every Corolla in town, eventually.”