I might be dating myself here, but I remember the days when the only safety feature a car had was it’s sheer size. The bigger of the two in an accident usually won. Seat belts didn’t exist, kids stood in the back window trying to get the trucker behind them to blow his horn and Mom sat in the middle of the bench seat, close to Dad, as they all motored down the highway.
In 1965, nearly 50,000 people just like them died.
While death rates are significantly lower today, the real impact of vehicle safety systems can be seen in the death rate per vehicle miles driven. In 1965, the rate of fatalities per 100 million miles driven was 5.03 compared to 1.10 in 2012. And with the technology being developed right now, the possibility of an accident and fatality free future is becoming a real possibility.
In The Beginning
Braking ability: the ability to bring a car down from high speed to a complete stop in a controlled manner in order to avoid a pending collision, was a matter of driver training and experience. We were taught to “pump” the brake pedal to come out of a skid when we had pushed the tires to the limits of their traction. (This technique was especially useful when driving in slippery conditions.)
The idea was simple enough. If the tires locked up due to the pressure exerted by the brakes, it broke traction from the road surface and steering control was immediately lost. To regain control, the driver had to momentarily release the brakes and get the wheel(s) turning again. The problems, though, were two-fold. First, a panicked driver often forgot to take their foot off the brake pedal and second, if the driver did raise their left foot, they weren’t slowing down and stopping distances skyrocketed.
Enter Anti-lock Braking Systems (ABS). First used on aircraft as far back as 1929, they didn’t make it to the automotive scene until the late 1950s, early 1960s and did not enjoy widespread use in production vehicles until the start of the 1970s. This was about the time that engine management duties were being turned over to a dedicated computer, and we began to witness the birth of the automotive electronic age.
Some early ABS systems (light trucks mostly) controlled braking only on the rear wheels. A single sensor, usually mounted in the rear differential, monitored the wheel speed and a single brake line led to a splice that fed the rear brakes. Because there is only one line being controlled, the system was referred to as a “one-channel” system. Both rear wheels need to lock before the ABS function would kick in and it was possible for one wheel to lock while the other kept turning, limiting brake effectiveness.
Adding the front wheels to a one-channel system created the three-channel, three-sensor ABS system. Each front wheel has its own speed sensor and is individually controlled by the system’s electronic control module. The rear, meanwhile, remains tied together on one line and uses the same single sensor in the rear end. Better, but still not ideal.
Adding dedicated lines and sensors to the rear introduced the four-channel, four-sensor system and most late model vehicles equipped with ABS use this platform. In all ABS systems, the idea is to monitor wheel speed and if it is found to be varying from the rest, the electronic control module alternately releases and applies the hydraulics to “pump the pedal” at a rate mere humans could never hope to match. This helped maximize emergency braking under a variety of (but not all) road conditions and did much to improve driver safety. To be effective, though, drivers had to be educated on the need to apply full pressure to the brake pedal and keep it applied, even when they felt the pedal rapidly pulsating under their foot. If released, the ABS system would disengage and the benefits of the system were lost.
Why Just for Braking?
If ABS could use electronic control modules to prevent wheel lock-up under hard braking, why couldn’t that same system be used to prevent wheel spin? This thought by some engineer somewhere (Bosch usually gets the credit) led to the development of Traction Control Systems (TCS). Also known by its (translated) European name, Acceleration Slip Regulation (ASR), traction control seeks to prevent wheel spin under acceleration. Think of it as ABS in reverse, with a twist.
What do you think of when you first hear the words “traction control?” At first, the function of the system appears obvious, doesn’t it? Traction is defined as “adhesive friction, as of a wheel on a track or a tire on the road,” and there are different kinds of traction. One, controlled by the ABS system, is braking. Another is under acceleration and yet another is when we turn. Traction control systems focus on the second, maintaining that “adhesive friction” under lateral (front-to-back) loads, the kind produced when we hit the gas.
It uses the same inputs as the ABS system does and controls the braking system using the same means, but there is one additional control it takes advantage of: throttle position. Out with the old cable-operated throttle body and in with the new electronic throttle body, complete with redundant accelerator position sensors. With these new mods, the TCS can reduce throttle opening, thereby reducing engine power, as a means to eliminate wheel spin when encountered.
Traction control worked well when faced with wheel spin caused by wet or icy roads as long as the car was traveling in a straight line. However, put that slick spot in the middle of a curve and reactions to the effectiveness of TCS were mixed and varied.
Forget the Yaw Factor
Your wife is heading home, the baby in the back seat securely strapped into his car seat. It’s been a rainy day; heck, a rainy week, and the roads are slick. As she heads down the hill just a few miles from home, the baby begins to wail and momentarily distracts her attention from the task of driving the car. She’s picked up a little speed on the downhill run, and as she nears the base she lifts her head back to the road just in time to see an F250 pulling out of a side street in front of her. She slams on the brakes and swerves to miss the truck, and she can feel the rear end brake loose and begin to swing around.
Instantly, the Electronic Stability Control system kicks in with no required input from the driver. The appropriate wheel brakes are applied or released as necessary to slow the car and end the fishtail. Disaster averted, everyone safe!
ESC is a result of the natural progression of onboard vehicle safety systems. Increased computer processing speeds, miniaturization of electronic components, and software development now allow the elements of the ABS/TCS systems to protect the occupants from loss of “adhesive friction” in turns. The addition of steering angle and yaw rate sensors allows the body roll to be monitored in addition to the existing sensors for acceleration/deceleration. All three axis of the car can be controlled with no outside input from the driver necessary.
The impact ESC has made on reducing deaths and injuries, especially from rollovers, is significant. According to the National Highway and Traffic Safety Administration (NHTSA) estimates, ESC will reduce single-vehicle crashes of passenger cars by 34 percent and single vehicle crashes of sport utility vehicles (SUVs) by 59 percent, with a much greater reduction of rollover crashes. They further estimate ESC would save 5,300 to 9,600 lives and prevent 156,000 to 238,000 injuries in all types of crashes annually once all light vehicles on the road are equipped with the system. Hence, the requirement that electronic stability control systems be installed on all passenger and light duty trucks (GVWR of 10,000 pounds or less) starting with the 2012 model year.
And while trained professionals can still do donuts with a car equipped with ESC, the majority of drivers will benefit from the addition of a system that will help keep the car stable under the majority of road and weather conditions.
Tech Points
With each step up, these onboard safety systems require a bit more from the servicing technician. Even performing routine tire and brake service can negatively impact the ability of these systems to work as they should. Let’s be clear, though. The foundation brake system should continue to function normally if there is a detected fault in the ABS, TCS or ESC, but these are vital SAFETY systems and you should be encouraging your customer to keep them working and serviced.
Many of the issues you will likely encounter with any of these systems will be due to a problem in the wheel speed sensor signals to the control module. Be aware of harness routing and plug connections when working around the wheel speed sensors. A little corrosion can go a long way to throwing off a signal, and connectors damaged by repeated use can keep a system offline.
Know that worn hub bearings can cause erroneous wheel speed data, and may not set a code but result in unwanted activation of the braking functions. A scope can be a very useful tool when isolating a weak sensor, an excessive air gap or damaged reluctor and, coupled with a micro-amp clamp, might be the only way to know for sure if a Magneto Resistive Sensor is on the last legs of its lifespan.
When performing any repair involving wheel position or steering column alignment on vehicles equipped with ESC, be sure to perform any required relearn of the steering angle and yaw rate sensors. As with any diagnostic dilemma, make the first stop your service information system and look for related Technical Service Bulletins (TSBs), especially for updated software requiring control module reprogramming.
What’s Next?
We laughed when we first saw the Google car, didn’t we? Visions of the robot car scene from Arnold Schwarzenegger’s movie, “Total Recall” spring to my mind when I think of an autonomous car. But the truth is, we aren’t that far from turning fiction into reality.
Right now, midrange consumer cars are coming off of the showroom floor with the ability to park themselves, warn their drivers when another vehicle is currently occupying the lane they are trying to move into, slow the car and blow bells and whistles when a front end collision is imminent and lots, lots more. And while they still require active participation from the driver, these systems are going a long way to protect the driver from others on the road and in some instances, protect the driver from himself (lane departure warnings, for example).
A year ago, I reported that the Department of Transportation and a “Who’s Who” collection of OEM and aftermarket industry leaders had joined together to conduct the first real world test of cars using vehicle-to-vehicle (V2V) communications. There were 3,000 cars equipped with what amounts to onboard WiFi and GPS and handed over to regular folks, who were asked to drive them normally and report back on their experiences.
Called Dedicated Short Range Communications (DSRC) devices, they allow a vehicle to communicate with other, like-equipped, vehicles and even with traffic infrastructure (toll booths, traffic lights). Unlike many of the systems in use today that utilize radar and/or cameras to detect threats, V2V does not rely on line-of-sight to be effective. It knows where everyone is, how fast everyone is going and what direction everyone is heading in.
Here’s a scenario for your consideration, and one I’m willing to bet you’ve really experienced. Ever pull up to a stop light, have the light turn green and just as you start to pull forward another vehicle (usually a really big 18-wheeler) blows through the light? A second earlier or later and you would have been struck dead center and likely killed or seriously injured. But with V2V, your car would know that the truck was coming and that it wasn’t slowing down. It would sound off warnings and flash red lights on the dash (or a heads-up display on your windshield), all in an effort to warn you to stay put. And if you ignore the warnings, it wouldn’t let you go anywhere until the way was safe even if you slammed the throttle to the floor.
The NHTSA thinks that this type of technology could eliminate nearly 80 percent of the accidents caused by a distracted driver and could save thousands of lives in the process. The pilot test in Ann Arbor, Mich., I reported on was phase two of DOT’s Connected Vehicle Safety Pilot program and NHTSA officials were cited as saying that, pending a successful outcome, rule making could begin in just a few years.
Truly autonomous technology is already here. On some European roadways, the concept of an auto “train” has been successfully proven. Drivers mate up with lead vehicles on the Autobahn, ask to join the train and when accepted, the lead vehicle takes over. The linked vehicles simply follow the leader while their drivers are free to read, catch up on their sleep or watch TV. When the final destination exit is near, the driver simply detaches from the train and resumes control of the car.
Several states here in the U.S. have issued special licenses for the testing of autonomous technology on their highways. Nearly every OEM has programs developing new and integrating existing technology into autonomous platforms. Couple the goal of accident-free operation with zero emissions and the move away from fossil fuel and you may live to see the day when your toddler son grows up to own a car cartoon icon George Jetson would be proud of; electric powered with hands-free operation. More importantly, the technology in use today (and the technology certain to come in the near future) may mean a near-zero loss of life on our nation’s highways about the same time.
Subscribe to Motor Age and receive articles like this every month…absolutely free. Click here
