Safety Rules the Road

Carmakers discovered over a decade ago that safety sells vehicles. This realization drove Chrysler to incorporate driver side airbags as standard equipment in 100 percent of their vehicles in 1988. More recently, manufacturers have added safety features like collision avoidance, LED daytime running lights and electronic stability controls to today's cars. Here's a look at recent developments.

Collision avoidance advances

Side Obstacle Detection and Lane Departure Warning (LDW) systems debut on the 2005 models in the Infiniti and Volvo. Infiniti's LDW system on the 2005 FX alerts the driver to an unintended movement out of the driving lane with a warning buzzer mounted under the hood. When the turn signal is used to indicate an intentional lane change, the system is disabled. Also, a switch in the passenger compartment can turn the system off. The system gets information from a single CMOS camera located on the rear view mirror and the vehicle's speed sensor. It then calculates the distance between the vehicle and the lane markings and the lateral velocity to the lane marking. Operating above 45 mph, but only when the camera sees lane markers, the LDW system, built by Valeo, targets reducing lane departure maneuvers that are blamed for 55 percent of the fatal accidents in the U.S.

Volvo's 2005 model S60/V70 and XC70 vehicles have a Blind Spot Information System (BLIS) that uses a CMOS camera mounted in each of the outside rearview mirrors to look out for undetected vehicles when changing lanes. The camera takes 25 pictures per second, and the system compares them to determine when a vehicle is moving within a critical range of 31 x 9.8 ft on either side of the car. When a vehicle is in this range, a warning lamp by the appropriate door mirror signals the driver of the danger. BLIS operates at speeds above 6.2 mph, reacting to vehicles that are a minimum of 12 mph slower and a maximum of 43.5 mph faster. The vision-based system can operate during the day or at night but is disabled under poor visibility conditions such as fog or heavy snow.

Following on the heels of the large number of vision-based systems introduced at the 2004 SAE Conference, many more models with blind spot detection and even more complex long-range sensing can be expected within the next few years.

LED Daytime Running Lights

Light emitting diodes (LEDs) have been used for vehicle tail lamps for a few years, providing reduced reaction time of approximately 30 ms versus 200 ms for incandescent bulbs. The 2005 Audi A8 W12 marks the first use of LEDs on the front end of a vehicle in headlamp modules. The assembly from Hella uses white LEDs for daytime running lights (DRL). The LEDs consume only a fraction of the energy required for traditional incandescent lamps that draw 55W each for low beam and 65W each for high beam. Dimming the LEDs also provides the parking lamp function and draws only 0.5W. DRLs have been required in Canada to reduce multiple vehicle collisions since 1990 model year, following the lead of other far north countries such as Finland and Sweden. General Motors' vehicles have had DRLs as standard equipment since 1996, and today over 50 percent of the vehicles sold in the U.S. have them. With the potential to last the life of the vehicle, and the same intensity as xenon lamps, LEDs have a bright future for automotive headlamps.

Electronic Stability Controls

Electronic stability controls (ESC) have been rapidly increasing in Europe since engineers at Mercedes added the system as standard equipment in their new A-Class in 1997. In 2002 over 27 percent of European vehicles had electronic stability control systems according to a Reed Electronics Research report on Automotive Electronics. However, in the U.S. and Japan the percentage was only about 5 percent. This could change rapidly as carmakers implement systems on an increasing number of vehicles.

ESC systems all function in a similar manner and are based on braking to maintain stability. A yaw sensor (gyroscope), lateral acceleration sensor, and steering wheel sensor provide additional input to the enhanced ABS system to slow down the appropriate wheels to prevent understeer (snowplowing) or oversteer (fishtailing). The added sensors, as well as the wheel speed sensors in the ABS system, allow the control unit to compare the vehicle's behavior to the steering wheel position. A typical system measures the driving situation every 7 msec or about once every 4 inches of travel at 30 mph. If the driver's intended path and the vehicle's actual path do not match, the system applies the appropriate braking action and/or reduces engine torque to restore stability.

A relatively recent advancement is the AdvanceTrac^(TM) with Roll Stability Control(TM) developed by Continental for Ford. By adding a second gyroscopic roll sensor, body roll angle and roll rate measurements allow the system to determine if the vehicle is about to roll. If this occurs, the system can reduce the engine power up to 15 percent and/or apply the brakes to one or more wheels to increase the vehicle's rollover resistance. The system is standard on 2005 Ford Explorer, Ford Expedition, Mercury Mountaineer, Lincoln Aviator, and Lincoln Navigator models, adding to other Ford models that already had ESC. Other manufacturers have had ESC on some models and are adding ESC to more vehicles. For example, GM began installing stability enhancing systems in 1997 and has more than 2 million vehicles on the road today.

Now Something Completely Different

A different approach to stability that does not rely on braking is Quadrasteer. Delphi's electronically controlled four-wheel steering system has been in production vehicles for over two years and is now offered on seven full size trucks and SUVs. With four-wheel steering, the degree of vehicle yaw required for a turning maneuver is reduced, in turn providing for increased stability. At speeds greater than 40 mph, the front and rear wheels steer in the same direction. However, below this speed the rear wheels steer in the opposite direction for maneuvering into tighter spaces. For trailer towing, turning the rear wheels reduces trailer sway or articulation between the truck and trailer. Delphi plans to add handling enhancement algorithms or integrate the system with an ESC system for even greater stability control.

Another alternative to brake-based stability control is Delphi's Active Stabilizer Bar System (ASBS) that will be offered for the first time on a 2005 Chrysler model. The system uses steering angle, lateral acceleration, and vehicle speed sensors to provide input to the electronic control unit to adjust the stabilizer bar force and reduce vehicle roll. A high articulation linear actuator and torsion bar or a rotary actuator provides control of body roll angle when cornering or in severe steering maneuvers, especially those that could occur in sport utility vehicles. ASBS can be integrated with other systems, including brakes and steering, for enhanced stability and control.

Stay tuned, as advances in core technologies will lead to even greater safety features in the future.

Contact Contributing Writer Randy Frank at [email protected].