Stopping Distances for Big Rigs
Generally, at 65 mph the typical passenger car or light pickup truck driver will travel a total of 316 feet from the first awareness of danger before coming to a final stop. The semi-truck driver takes much longer traveling out 525 feet before coming to a final stop. In the reconstruction of a truck accident the stopping distance of the tractor–trailer can be a critical component.
It is common knowledge that a big rig takes much longer to stop than a passenger car or pick up truck. Calculating the stopping distance for any vehicle involves several different factors.
PERCEPTION OR REACTION DISTANCE
Perception and reaction time did not very between passenger cars and large trucks. The general assumption for reaction time for the average driver is 1.5 seconds, which is the time it takes the driver to perceive a situation and also hit his or her brakes. Obviously the faster the vehicle is traveling at the time the perception/reaction time starts the further the vehicle travels before stopping.
DIFFERENCES IN WEIGHT
Tractor–trailers have larger brakes than passenger cars or light pickup trucks, however due to their weight it takes the big rig much longer to stop than a passenger car. Generally a big rig can weigh up to 80,000 pounds, while a passenger car may weigh about 5000 pounds. General stopping distance calculation at 40 mph indicates a passenger car or light pickup truck can come to a full stop in 124 feet from the driver perceiving the danger. The big truck at 40 mph however, travels 169 feet after the driver first perceives the danger before final stop.
STOPPING AT HIGHWAY SPEEDS
Generally, at 65 mph the typical passenger car or light pickup truck driver will travel a total of 316 feet from the first awareness of danger before coming to a final stop. The semi-truck driver takes much longer traveling out 525 feet before coming to a final stop.
Obviously, the general calculation can vary depending on the specific circumstances involved in the truck accident.
Factors affecting braking distance for passenger cars and pickup trucks are the condition of the roadway and also the weather conditions. Rain, ice or snow can increase braking distance substantially. Additionally the condition of the roadway and its coefficient of friction can play a part in the calculation of the expected stopping distance of a commercial vehicle. Also, when the danger can actually be perceived can play a factor in the stopping distance calculations. Such things as obstructions to the vision due to weather or for other reasons can delay a reasonable drivers ability to recognize a danger. Too, the tread on the tires of a large truck and how the brakes are applied as well as the specific condition of the breaks involved will impact stopping distance.
HEIGHT AND PERCEPTION
Scientific studies of highway design and safety have come a long way in the last 20 years. Numerous studies indicate that a variety of factors such as a driver’s height above the roadway can play a significant factor in the initial perception of danger. Clearly, big rigs have a substantial advantage in being able to perceive a danger earlier due to the ability to see further ahead because the driver is elevated above the roadway. This advantage gives professional truck drivers the ability to perceive traffic situations earlier than a passenger car and also take steps to minimize the danger. Passenger vehicles and particularly those traveling closely behind other vehicles can be at a distinct disadvantage it and perceiving traffic situations in front of them.
Almost all of the recent commercial trucks contain one form or another of an onboard computer. Those devices will calculate many things for a trucking company and also can keep track of vital factors after an impact. Such things as pre-impact speeds and when the brakes were actually activated are usually shown on an onboard computer print out after a truck accident. While the data presented from an onboard computer will vary depending on the device and the manufacturer, the material can be invaluable in reconstructing the actual acts of the truck driver in the accident scenario. It is highly recommended that counsel for any party to a truck accident lawsuit obtain the onboard computer data as early as possible in the litigation.
Stopping distance calculations for big rigs can vary depending on many different factors and counsel should look first to the onboard computer data to develop an accurate and precise reconstruction.
Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer. For specific technical or legal advice on the information provided and related topics, please contact the author.