Proper speed management means operating at the appropriate speed for all road conditions. Proper space management means maintaining enough space around your vehicle to operate safely.
Speed & Stopping Distance – 4 Factors involved in stopping a vehicle
- Perception distance
- Reaction distance
- Brake lag distance
- Braking distance
Perception Distance – the distance a vehicle travels from the time you see a hazard until your brain recognizes it. The perception time for an alert driver is approximately 3/4 of a second. At 55 mph a vehicle travels about 60 feet in 3/4 of a second.
Reaction Distance – the distance a vehicle travels from the time your brain tells your foot to move from the accelerator until your foot hits the brake pedal. The average driver has a reaction time of 3/4 a second. At 55 mph that accounts for another 3/4 a second and another 60 feet traveled.
Brake Lag Distance – when operating a vehicle with air brakes, it takes about 1/2 a second for the mechanical operation to take place.
Braking Distance – the distance it takes a vehicle to stop once the brakes are applied. Braking distance is affected by weight, length, and speed of the vehicle as well as road conditions. A heavy vehicle’s components (brakes, tires, springs, etc.) are designed to work best when a vehicle is fully loaded. At 55 mph on dry pavement with good brakes, a heavy vehicle travels about 170 feet and can take about 5 seconds to stop. When you add together the perception, reaction, brake lag and braking distance, at 55 mph it will take between 6 and 7 seconds to stop and the vehicle will travel about 290 ft (almost the length of a football field) in ideal conditions. Higher speeds increase stopping distance greatly.
Speed & Road Conditions Tractions – necessary for vehicle control. The less friction between a vehicle’s tire and the road, the less traction. Certain road conditions reduce traction and lower speeds are necessary.
Rain – can affect a vehicle’s traction. As rain beings to fall, it mixes with oils on the road, causing the oils to rise to the road’s surface. Until additional rain breaks down and washes away these oils, there is a layer of slippery oil between a vehicle’s tires and the road. This condition can last anywhere from a few minutes to a few hours.
Speeding seems pretty harmless most of the time until you need to stop to avoid having an accident. Slowing down and driving the speed limit will give you the time to stop. Distractions like talking on the phone or just plain not paying attention will add more time and distance to be able to stop.
Being focused while you are doing your job is the most important part of keeping you and the world around you safe.
Dave Zerbe – Safety Director
