delay and shorter stopping distances provided by hydraulic disc brake systems with ABS will result in safer vehicle operation. Te history of brake development and technology in trucks and automobiles spans more than a century, and school buses over many decades. What matters most, however, is not the decades of development, but rather the milliseconds of the application. As with many things, consumers drive demand. After experiencing the safety and convenience of hydraulic-powered, anti-lock brake systems with traction control in automobiles, many school fleets and air brake users desire the same convenience. Tis generation of drivers has learned— and future generations will continue to learn—how to drive in vehicles with ABS, traction control and electronic stability con- trol. Allowing time for air pressure to build or pumping hydraulic brakes on ice, is an antiquated idea for many of today’s drivers. Familiarity with these newer systems
breeds habit, and habits can be hard to break, especially in an emergency-driving situation. Based on physical design alone, hydraulic disc brake systems with ABS will stop in shorter distances than comparable air brake systems, as compressibility of air contributes to delays in braking perfor- mance. Hydraulics, however, are virtually incompressible, resulting in reduced delays in ABS brake application.
Allowing time for air pressure to build or pumping hydraulic brakes on ice, is an antiquated idea for many of today’s drivers. Familiarity with these newer systems breeds habit, and habits can be hard to break, especially in an emergency-driving situation.
With medium-duty truck school bus chassis in the 26,000- to 33,000-pound range, there is much to consider when specifying brakes. When the school bus duty cycle, cost-benefit analysis of air brakes versus hydraulic brakes, and CDL driver availability are factored, valuable insight will be gained regarding the optimal brake system for the type of school bus in your urban or suburban fleet operations.
Robert T. Pudlewski has over four decades of experience in the school bus industry. He is the retired vice president of fleet operations, procurement and maintenance for Laidlaw.
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