The Nightmare: guiding 50,000 lbs. down the road when the unimaginable happens – suddenly and seemingly out of nowhere a person stumbles and falls directly in front of your city bus. Without even a second to think about it, you instinctively and immediately slam the brake pedal to the floor. That’s all you can do. The rest is left to fate. Or is it?
On May 6, 2017 this is what befell Palm Tran bus operator Thomas Guthy while driving his route in West Palm Beach, Florida; when a woman stumbled into the street right in front of his moving bus. He had but one option. Was it enough to avert disaster?
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Thanks to the fast reaction of Mr. Guthy, the bus stopped just in time to avoid a tragedy, probably saving this pedestrian’s life. Mr. Guthy was appropriately recognized by Palm Tran’s leadership for his commitment to safety. “Either fate or maybe there’s another plan. Someone’s up there watching out for her and just happened to be me,” Guthy said in an interview. “Just a normal day for me, really. There’s other heroes out there, man. Other heroes.” Other heroes indeed.
A braking cycle of total stopping distance begins with a decision to slow or stop a vehicle. The beginning of this cycle is the reaction time, from the driver’s decision to actually stepping on the brake pedal. As in this real-life example, reaction time is critical, but braking distance, i.e. what happens AFTER the driver steps on the pedal, can literally be the difference between life and death.
Stopping a massive motor vehicle, while a simple concept, is actually a complex series of interdependent processes, beginning with a thought (the decision to stop), followed by the action of a foot pressing the brake pedal, transmitting air pressure through a series of valves and hoses, ending with a brake force of disc pads gripping a brake rotor to generate enough brake torque to come to a stop. The total time of this event; sometimes occurring in less than two seconds. The engineering and physics used to design and manufacture these systems are considerable, to say the least.
Maximum allowable stopping distances are clearly defined by law. When it comes to their transit buses Palm Tran validates the brake performance of each unit using a sophisticated tool
, known as the Vericom Computer brake meter. This instrument tests the brake performance of the bus to confirm that it meets or exceeds minimum braking and stopping distance requirements. After a brake job, each bus is tested before being certified as ready for service.
While Palm Tran buses must stop within the maximum 20mph stopping distance of 25 ft., it is expected that each bus will stop in a shorter distance. An example of a Vericom Transit Report shows just that. In this particular example the measured stopping distance at 20mph is 19.7 ft.; a 5.3 ft. improvement under the standard of 25 ft.
Vericom VC4000PC Brake Meter
While a 25 ft. stopping distance might be “good enough” to pass inspection, it may very well have not been good enough to save the life of a West Palm Beach pedestrian on May 6th, 2017. We will never know for sure.
At Power Brake, exceeding typical brake performance and longevity standards is our mission. With so much dependent on your brakes, for us, and our customers “good enough” is NEVER considered good enough.