Tech Briefs
Heavy-duty truck safety systems

The Roll Stability Advisor from Freightliner communicates messages with increased urgency as the potential for rollover increases. Line Guidance detects lane drift and warns drivers with an audible alert. The system's digital camera gathers visual data, digitizes them, and feeds them into a CPU.

Freighliner Corp.'s Roll Advisor & Control is a truck safety feature designed to help prevent rollover accidents. Available later this year, the new feature will be standard equipment on Freightliner's new Century Class S/T (safety/technology) heavy-duty truck. Freightliner is North America's largest heavy-duty truck manufacturer and is a leading manufacturer of Class 4-8 vehicles.

According to the Department of Transportation, rollover crashes account for about one-half of the 700 annual heavy-duty truck driver fatalities, while also causing serious injury and death to other motorists. The Roll Advisor & Control system is intended to deter rollover crashes by alerting the truck driver to potentially dangerous driving behaviors and/or automatically slowing the vehicle to help prevent rollover. The new system has two integrated components: Roll Stability Advisor and Roll Stability Control. Both use sensors integrated into the truck's anti-lock brake system. By tracking the truck's lateral acceleration and wheel speed, the system detects the potential for rollover.

Roll Stability Advisor is a training aid designed to advise the driver that he or she is operating the vehicle in near-rollover conditions. Warnings are communicated via the Driver Message Center, an easy-to-read display located in the dash, directly in front of the driver. As the potential for rollover increases, warning messages are displayed with increased urgency. The first level of alert is a message that reads "Risky Maneuver Detected." The second level of alert involves an alternating message that reads "Rollover Risk Detected," which will continue to be displayed until the driver pushes a button to acknowledge it. The third level of alert involves an alternating message that flashes "High Risk of Rollover Detected." At this highest level, a tone also sounds to signal that a high rollover risk event has occurred.

Instances of advisor warnings can be recorded in Freightliner's data logging unit, an electronic memory device that records data on truck and component performance. Fleet managers can download information on rollover warnings and, if necessary, coach drivers on safer driving techniques.

The Roll Stability Control function takes rollover prevention to the next level by automatically slowing the vehicle. When sensor data indicate that a rollover is imminent, it sends a signal to the engine's electronic control unit to reduce engine power and apply the engine brake. When the vehicle becomes stable, power is restored and the engine brake is turned off.

"Roll Stability Control demonstrates the benefits of integrated, electronically controlled truck components," said Gary Rossow, Director of Government Technical Affairs for Freightliner. "In this system, the anti-lock braking system and engine work together to dynamically control the vehicle." Rossow called the system a logical extension of anti-lock brakes, which became required equipment on heavy-duty tractors in 1997 and trucks in 1998. Freightliner made anti-lock brakes standard on its Class 8 trucks in 1995, well ahead of the federal mandate. The company plans to make Roll Advisor & Control functions available on all its air-braked vehicles. The system was developed in conjunction with Meritor WABCO.

Another active safety system now available from the company is Lane Guidance, a lane-departure warning system. To be available later this year on Freightliner Century Class S/T, Columbia, and Argosy heavy-duty trucks, the new system monitors the truck's position relative to lane markings, then sounds an audible warning when the truck is about to stray outside its lane.

The system consists of a digital camera mounted on the windshield inside the cab, a central processing unit (CPU) located in the overhead console, two speakers located in the left- and right-side doors, and associated wiring. Using proprietary DaimlerChrysler image-recognition software and a lane-recognition algorithm, the CPU determines if a vehicle is drifting too close to the lane markings. When this occurs—and if the driver has not activated the turn signal—the CPU sends a signal to emit a distinctive "rumble strip" sound.

When the truck is straying to the left, the warning sound comes from the left speaker, and, when the truck is straying to the right, it comes from the right speaker. The company believes that the driver will intuitively steer away from the side of the sound. The rumble strip sound was chosen after research showed that it effectively warned drivers without causing them to overreact.

Lane Guidance works both day and night and in most weather conditions. The system tracks most types of lane markings common in North America, including dashes and dot-type reflective markings (commonly called "bot dots"). A change of lane width or merging/splitting of the lane should not cause an alarm. The system is capable of transmitting and receiving messages on the J1939 data link and is designed to be maintenance-free. A warning light on the dash serves to indicate any problems with the system. According to the company, the system will stand up to the normal rigors of the truck environment such as vibration, shock, temperature, humidity, and dust.

Freightliner's Lane Guidance System was developed with Odetics ITS Inc. and Daimler-Chrysler Research (Freightliner is a Daimler-Chrysler subsidiary). Odetics ITS is an Anaheim, CA-based company specializing in intelligent highway technologies.

Jean L. Broge