Regular readers of this column are aware that I frequently promote increased oversight in the areas of at-risk driver behavior identification and management. That dedication is based on two tenets: the correlation between crashes and at-risk behavior; and the crash reduction benefits that can be achieved through monitoring and coaching of at-risk drivers.

However, I also recognize that today's drivers should have access to enhanced truck safety systems since they face increasingly hazardous traffic conditions.

More technologically advanced brakes for Class 8 vehicles are a case in point. They have been shown to provide increased braking stability and reduced stopping distance. Such Class 8 truck brake advances include:

  • All-wheel air disc brake systems;

  • Steer axle air disc brakes and rear axle(s) high-performance wide drum brake hybrids;

  • All-wheel high-performance wide drum brake systems.

Air disc brakes provide interesting advancements over drum brakes since they are not prone to brake fade.

For example, a 2004 NHTSA report noted that the stopping distance for a fully loaded Class 8 tractor going 60 mph and equipped with air disc brakes at all wheel positions was 232 feet. This is 21% less than the 291 feet needed to stop a tractor equipped with standard S-cam drum brakes. The report also noted that the results were nearly as impressive when only the front axle was equipped with disc brakes: 255 feet.

The results of that report were cited in a 2005 NHTSA NPRM, which called for a 20% to 30 % stopping distance reduction for Class 8 tractors. While NHTSA has not yet published the final rule, most industry observers recognize that the crash reduction benefits of improved stopping distances outweigh the costs of equipping vehicles with advanced braking systems.

Although enhanced and reliable air disc brakes have been available in North America since 2001, the deployment rate is extremely low. One manufacturer estimates that just 1% of all Class 8 trucks are equipped with air disc brakes. In Europe, on the other hand, over 2-million air disc brakes are installed each year.

Why the disparity? Brake manufacturers mention the unfavorable performance ratings given earlier models; the paucity of cost/benefit data demonstrating ROI; and resistance to change among maintenance technicians and fleet operators.

Until recently, I counted myself among the air disc brake naysayers. As an owner-operator in the 1980's, I purchased a vehicle equipped with air disc brakes. While the performance of these brakes was superior to drum/shoe systems, the truck was plagued with brake caliper adjustment and rotor warping issues.

Based on a recent brake technology demonstration, however, I have reversed my opinion of air disc brakes. Current systems employ internal automatic adjusters which are sealed and lubricated for life. Rotors are now larger and manufactured using sophisticated metallurgical techniques, and the brake pads can now be equipped with electronic wear indicators.

I urge you to revisit the safety benefits of air disc brakes. These brake system combinations (e.g., all-disc or hybrid front disc/rear drum) provide demonstrated improvements in stopping distances, braking stability and fade resistance. Given today's highway environment, your drivers will be better equipped to navigate the all-too-common hazardous traffic conditions.


Jim York is the ass't. vice president of technical services for Zurich Services Corp. Risk Engineering in Schaumburg, IL.