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Truck Accidents – Comparing Trucks to Cars

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Smaller Truck Wreck

Trucking Accidents: Differences Between Large Trucks and Cars

While the differences between large trucks and cars appear obvious to most, each year there are thousands of accidents that could have been avoided had traditional safe driving rules been followed. Underlying the majority of the differences between large trucks and cars is simply their difference in weight. In general, large tractor-trailers (18 wheelers) and their cargo have a maximum allowed weight of 80,000 pounds. The average car on the highway weighs roughly 4,000 pounds, or 1/20th of a fully loaded truck. This huge disparity in weight can have a massive effect on how large trucks and cars interact on the roads.

Due to the sheer weight of large trucks on the roads, tractor trailers have specialized brakes in order to help them slow their cargo. Like other large vehicles, tractor trailer trucks use compressed air brakes rather than hydraulic braking systems found on regular cars. Use of air brakes connects the systems for both the truck and the trailer, giving the driver control over all systems through the cab. While air braking is effective, it is not supernatural. Given the large loads trucks generally carry, they require significantly more room and time to stop. According to the Utah Department of Transportation, a large truck traveling at 55 miles per hour requires 100 more feet to stop than a car, and a large truck traveling at 65 miles per hour requires over 200 more feet. Furthermore, the compressed air braking system poses unique maintenance issues. Compressed air naturally carries water moisture which can affect braking ability. Some trucks have a drying system that prevents brake failure by removing all water from the compressed air used in their brakes. Trucks without this feature, however, can be at risk for brake failure, particularly in colder weather where freezing is more likely.

In addition to the effects weight can have on a large truck, how that weight is distributed is also important. Given the physics of how a trailer works, loads that are distributed more evenly over the floor of a trailer produce a far more agile and easy to control vehicle. Loads that are stacked high off the floor of the trailer and are not spread out across the entire trailer have a negative effect on handling ability. As a result, a large truck becomes even more difficult to maneuver at high speeds.

The final significant difference between large trucks and cars is their visibility. Not only are trucks large and easy to spot on the roads, cars have windows on all four sides, giving the driver the ability to see what is in front of, next to, and behind at all times. Cars, on the other hand, are relatively small and hard to spot. Furthermore, trucks have massive blind spots on their sides just in front of the cab, just behind their side mirrors, and directly behind their trailers. Large trucks not only have the added burdens of weight, inability to stop as quickly, and lack of agility, but the operators also have a harder time seeing the other vehicles on the road.

Below is information on stopping distances

How to determine Stopping Distance

Total stopping distance is the distance your vehicle travels from the time you see a hazard and press on the brake until the vehicle stops. Total stopping distance is made up of three parts:

  1. Perception Distance – The distance a vehicle travels while a driver is identifying, predicting and deciding to slow down for a hazard.
  2. Reaction Time – The time it takes for a driver to execute a decision once a danger is recognized. The distance your vehicle travels while you react is called a reaction distance.
  3. Braking Distance – The distance a vehicle travels from the time a driver begins pressing on the brake pedal until the vehicle comes to a stop.

For trucks, you must also factor in the brake lag distance in the stopping distance. Brake lag is the time it takes for a brake signal to travel to all the wheels on the tractor-trailer (about 3/4 of a second). Brake lag distance is the distance the truck travels before the brakes on the trailer are engaged.

Total Stopping Distances