You are here: Home / Articles / Technology / Telematics and Electronics / Keeping Your Distance Automatically

Keeping Your Distance Automatically

Cruise control has become smarter. Besides maintaining cruising speed, it can also maintain a safe distance between you and the vehicle in front of you. This new technology is called either Adaptive Cruise Control, Adaptive Speed Control, or Distance Sensing Cruise Control, depending on the auto manufacturer offering it. Like most new technologies, it is first being offered on high-end cars like selected Cadillac, Lexus, Mercedes-Benz, BMW, and Jaguar models. Typically, this new technologies adds $1500 to $2000 to a vehicle’s bottom line.

Actually, the technology is not brand new. Eaton Vorad has offered its Collision Warning System for eighteen-wheelers and buses for several years. The first “civilian” ACC system was offered on a Toyota luxury sedan sold in Japan in 1998.

Since these systems operate on the same basic principles, let’s look at the Cadillac DSCC system to understand how they work. The Cadillac system uses a 76-gigahertz radar sensor located behind the grille to measure the distance to the preceding vehicle. The system is controlled by switches on the turn-signal stalk and steering wheel, just like ordinary cruise control. A head-up display and driver’s information center provides visual information.

Set the cruise speed and the car will stay there, that is until the radar senses another vehicle up front. DSCC can detect not only cars and trucks, but even small motorcycles. Then it goes into “follow” mode to slow the vehicle down to match the speed of the preceding vehicle and thus maintain a constant following distance. This distance is set by pressing + or - on the "Gap" switch on the steering wheel. Pressing the + side will increase the distance from one second to a maximum of two seconds following distance, equating to a safe distance when traveling at 60 mph. Should the vehicle ahead turn or move over to the next lane, DSCC will automatically accelerate the car back to the cruise control's set speed.

If another vehicle suddenly moves into the lane ahead, and the following distance is less than the preset separation distance, that is the one-to-two second interval, brakes will be applied until the distance is safe again. Should the road curve, DSCC will detect the sharpness of the curve and alerts the driver with a TIGHT CURVE message while slowing the car to negotiate the curve safely. If the separation distance decreases suddenly, indicating a possible collision or just the preceding vehicle braking suddenly, a red warning is flashed, the radio speaker emits a chime warning and brakes are applied. However, since the system may not detect a stopped vehicle quickly enough to warn the driver and allow enough reaction time, you must still stay alert.

While most systems use radar for detecting vehicles ahead, some use LIDAR (light detecting and ranging.) One of the problems is that snow, rain and dirt can affect the operation of these systems, especially those using LIDAR. For example, in the Lexus that uses LIDAR, the system will automatically shut off if the windshield wipers are turned to a rapid setting, indicating heavy rain or snow; if something activates the anti-lock braking system or if the vehicle skid control system detects the slipping of tires indicating wet weather. Cadillac drivers may get a message that DSCC is not available if they have been driving in inclement weather. Wash off snow or dirt of the Cadillac grill crest and the system is back in operation.

In today’s lawsuit happy environment, the auto companies have opted to call these as “drivers’ aids” rather than “safety systems.” By doing this, they hope to avoid any lawsuits from collisions involving vehicles equipped with ACC or DSCC.

As a piece of interesting automotive history, speed cruise control was invented by Ralph Teetor, a talented engineer and major player in the automotive industry. He was president of the Perfect Circle Corporation and served a term as the president of the Society of Automotive Engineers. He built his first car at the age of 12. He received his first patent for a speed cruise control device in 1945. Before settling on the name “cruise control,” it was called Controlmatic,” "Touchomatic,” “Pressomatic,” and “Speedostat.” Cruise control first appeared on 1958 Chryslers and became standard on Cadillacs in 1960. Oh yes, Teetor was blind from the age of 5!