GIVING SCHOOL BUSES A Brake Te answer can be found in the most important safety
feature on a school bus – the brakes. Most certainly post-mortems will be performed on both
buses involved in the Missouri tragedy to ascertain the con- dition of their safety features, but industry experts agree that the brakes remain the primary safety feature on any vehicle. “I wholeheartedly agree with that observation,” says Ran-
dy Petresh, vice president of technical services at Haldex Commercial Vehicle Systems Inc., which manufactures air brake systems. “I’ve been doing this for 35 years, so I have pretty strong feelings on that topic. But, unless you work in the industry, you probably don’t see it or realize how much effort goes into developing brake systems.” Te level of sophistication and engineering excellence
achieved by the manufacturers of these technological marvels could raise eyebrows at NASA. Everything from metallurgy to electronic sensors to radar comes into play. However, in the on-going debate about school bus safety
devices, i.e., seat backs, seat belts, cameras, lights, etc., little is said about brake systems outside the circle of those di- rectly involved in developing, using or regulating them. Raybestos Brakes & Chassis states on its Web site that “…
brakes are the most vital system to the safety of the vehicle,” which could be the anthem for the industry. Doug Harmon, product manager for heavy duty brakes at Raybestos Commer- cial Vehicle Group says, in his world, it’s either “air” or “juice.” “Whether it’s air or hydraulic brakes, these systems are
pretty robust and will take a lot of abuse before they fail,” he says. “We make aftermarket parts for hydraulic systems and the friction material for air brake systems. Our prod- ucts equal or exceed the quality of the original equipment. Tat’s important because school districts should make sure they have a reputable aftermarket supplier to maintain the integrity of the brake systems.” School officials and manufacturers say the stopping abil-
ity of current brake systems exceeds federal requirements, and expectations are the technology will approach some- thing akin to Star Trek efficiency in the future. “Tere is some very good braking technology out there,
when it’s used correctly,” says Mike Kenney, regional trans- portation coordinator for Washington State. School districts may choose either hydraulic or air
brake systems up to a gross vehicle weight rating (GVWR) of 28,000 pounds. At 28,001 pounds, NHTSA mandates air brake systems that stop the bus within 335 feet from a maintained speed of 60 mph. Hydraulic brake systems must stop a bus with a GVWR of more than 10,000 pounds within 280 feet from 60 mph. Minimum spacing between school buses that “caravan” on interstates is a local pre-
64 School Transportation News Magazine October 2010
Oct10_STN.indb 64 9/14/10 12:18 PM Bu
rogative and ranges from 300 feet to a quarter mile. Te three- or four-second rule is also applied. Bus-to-bus com- munications make it unnecessary to follow any closer. While federal and state standards lean toward air brakes
as the more effective system at heavier GVWRs, local dis- tricts have some say based on preference, geography, budget and terrain. “Most states west of the Mississippi River require air
brake systems on the larger buses, says Bruce Little, Colo- rado’s state director of student transportation. “We require air brakes on our buses with a capacity of 54 or more. East of the Mississippi, most states have no preference or they specify hydraulic systems. Tradition in mountainous west- ern states is that air brakes are preferred.” Haldex’s Petresh adds that air brake systems are also
more complicated. “Air brakes are more sophisticated with many moving parts,” he says. “A CDL is needed to operate a vehicle with an air brake system, so it’s easier to find drivers for school buses with hydraulic systems. Which one is safer is subjective. You do have secondary braking systems.” Secondary braking systems, also known as engine retard-
ers or frictionless braking systems, are fail-safe systems for the service brakes. Developed for travel in mountainous areas, the popularity of these optional systems has spread. Te most effective retarder system is the electromagnet-
ic braking system. It creates a magnetic field that slows the drive line. Tese frictionless systems are popular not only for safety; proponents say they extend the life of the service brakes and reduce maintenance costs. “Our biggest school bus customers are in the mountain-
ous areas, but electromagnetic braking systems are suited for all types of roads,” says John Engler, regional manager for Telma Retarder, Inc. “Our frictionless brake system reduces stopping distances by 33 percent at all speeds on any terrain.” Ron Johnson, shop manager for frictionless braking man-
ufacturer KLAM America Corporation, says the retarders are not meant to stop the bus completely but to give driv- ers an edge by working in conjunction with the service brake. He adds that retarders have evolved from a manual hand control to an automatic foot control activated by pressure on the brake pedal. “If the ABS application is sensed, the retarder is automat-
ically turned off to prevent locking up the brakes,” Johnson explains. “We sell more of the foot control because it’s the latest, best technology.” Manufacturers say the next generation of brake system
technology for school buses is already available, but change in the industry is slow and will take a few years. “Te more sophisticated technology adds cost,” says
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