car in the distance with its brakes on followed by a semi truck that needs to stop appropriately

5 Things That Affect Stopping Distance

Truck driving requires constant consideration of a number of things to make sure the truck, its cargo, and the other drivers stay safe while on the road. One consideration that truck drivers must always be thinking about is stopping distance, which, as every experienced truck driver knows, is a lot more complex than just speed and response time. There are five main external factors that can affect a truck’s stopping distance and knowing what they are and how to respond to them is crucial to maintaining control and avoiding accidents.

1. Traction

Traction is the resistance between a tire and the ground that allows the tire to exert enough force on the road to change a truck’s direction or speed. This resistance is reduced when the road surface is slippery, decreasing the tire’s ability to exert the force necessary to control the truck. This loss in traction increases stopping distance, sometimes doubling the amount of time it takes a truck to stop when driving on wet roads. Since truck drivers cannot control road conditions and must still drive during less-than-ideal weather, they must adjust the one thing they can control—speed. Driving a truck at a lower speed can counteract the reduction in traction. The slickness of the road surface determines how much a truck driver should reduce their speed.

  • In rain, water, and fog – Speed should be reduced by about a third. For example, if the speed limit is 55 mph, drive 35 mph.
  • On packed snow – Reduce speed by half or more.
  • When there is ice on the road – Don’t drive. Slow to a crawl and stop as soon as it is safe to do so.

Ice is the most dangerous road condition for drivers because it virtually eliminates traction. One way to know if there is ice on the road is by opening the window and feeling the front of the mirror or the antenna. If either one has ice, then the road is likely starting to get icy, too. Another way is by watching vehicles as they pass. If the road appears wet but there’s no spray coming from other cars as they pass, then the road is probably icing up with black ice. Keep in mind that bridges and overpasses ice up first, so be extra cautious when driving over these.

2. Hills

On a hill, gravity affects the motion of a truck, which in turn impacts the truck’s stopping distance. When a truck is driving uphill, gravity is pulling the truck backwards, which helps the truck stop more quickly. On a downhill, gravity is pulling the truck forwards, which increases the amount of time it will take the truck to stop. This is why truck drivers need to be aware of their speed and make sure they are not driving too fast downhill. Some factors drivers need to consider when determining what speed they should maintain on hills include the weight of the truck and its load, the length and grade of the hill, and road conditions. Slowing to an appropriate speed and downshifting prior to the start of the downhill will help truck drivers maintain a safe speed and stopping distance as well as save their brakes and prevent overheating.

3. Curves

Traction is required for changing both the direction and speed of a truck. When a truck goes around a curve, it must slow down and turn, and trying to do both simultaneously places the truck at a greater risk of losing traction. If a truck loses traction in a curve, it will continue straight and drive right off the road or be unable to stop if needed. To avoid this, it is best to slow down before the turn and then gently accelerate out of it, if possible. It is often necessary for truck drivers to reduce their speed lower than the posted maximum safe speed so that the truck’s higher center of gravity will not cause the load to tip while turning.

4. Traffic

For stopping distance and general traffic safety, the safest speed for a vehicle in heavy traffic is matching the legal speed of the surrounding vehicles. There is less of a chance of vehicles running into one another when they are traveling at the same speed in the same direction. However, truck drivers are not always able to follow this unwritten safety rule. Many states reduce speed limits for commercial trucks on highways and interstates, sometimes up to 15 mph below the regular posted speed limit. In these situations, truck drivers must be extra cautious when changing lanes because the vehicles around them may be going much faster with increased stopping distances.

5. Visibility

Visibility has a large impact on stopping distance. If you cannot see in front of you, then you don’t know that you have to brake. Truck drivers need to be prepared and able to stop within the visible distance in front of them. If visibility is poor due to darkness, fog, rain, following distance, or other conditions, then truck drivers should reduce their speed to decrease their total stopping distance. Truck drivers should also avoid riding too closely behind other vehicles so that they can see what lies ahead and have enough time to stop if needed.

Drive for the Best Transportation Company in Knoxville, TN

Here at Roane Transportation, our first priority is our truck drivers’ safety, followed by the safety of the loads we transport. We take all the necessary precautions to ensure safety, including keeping our drivers informed of new safe driving practices and providing them with the latest equipment. If you want to drive for a transportation company that values its drivers and does whatever it can to keep them safe while on the road, come drive for Roane Transportation. We are a Knoxville-based transportation company with local, regional, and national fleets, so you can choose to stay close to home or see the whole country as you drive for us. Give us a call at 865-354-3288, contact us online, or fill out an application today to start your truck driving career at Roane Transportation.