Compounding this problem is that many fleet vehicles on the road today are already chronically overloaded because they are under-spec’ed for their payload requirements. Overextending a truck’s payload capacity beyond the chassis’ weight specifications shortens its service life. Overloading results in increased tire failure because they run hotter, lower fuel economy, faster brake wear, and unnecessary downtime due to premature wear-and-tear on the engine and transmission. In addition, an overloaded truck is a rolling time bomb in terms of liability exposure. Statistics show that trucks are involved in one out of every nine road traffic accidents. According to NHTSA, although trucks make up just 4 percent of all registered vehicles, in 2002 they were involved in 21 percent of all passenger vehicle occupant fatalities in multiple-vehicle accidents. As a result, commercial truck accidents are litigation magnets. An overloaded vehicle takes longer to stop and is more likely to be involved in rear-end collisions during an emergency stop situation. The increased weight of the vehicle causes its braking distance to increase, which can cause a driver to misjudge stopping distance. Overloaded trucks go slower on upgrades and, conversely, faster on downgrades. When the brakes of an overloaded truck are forced to work too hard, they can fail and result in an accident. Emergency handling capabilities of an overloaded vehicle are also reduced, which can contribute to a preventable accident. Drivers are employed to make deliveries, and most deliveries have tight deadlines. Typically, drivers in danger of missing a deadline, drive faster. All too often, this can result in an accident. In addition, excessive payload can affect a driver’s ability to control a truck. Loads that are unbalanced, overweight, or shift in transit can cause a driver to lose control. If the load shifts when making a lane change or a sudden turn, g-forces can cause a rollover. A Proactive Solution is to Spec “Reserve” GVW
In my mind, payload requirement is the most critical aspect of truck spec’ing. How much weight will a truck need to carry in its daily workload? Determining the correct size of a vehicle for the intended payload requires a judgment call on how much payload overcapacity to spec into a vehicle. Spec’ing a truck to the minimum necessary payload rating by basing it on an average load (or looking at only today’s business needs instead of anticipating future needs), means that the vehicle will operate at peak capacity most of the time. This may compromise safety and reduce the length of its service life. Using average payload for specs means that the vehicle will sometimes be overloaded resulting in excessive wear and tear, higher maintenance costs, and reduced fuel economy. When spec’ing a vehicle, determine the maximum payload need, not an average. The vehicle must be able to meet its fleet application every day with the maximum load at any given time. However, as a word of caution, having too much payload capacity is wasted capacity that should likewise be avoided. The best way to handle this is to allow for a specific “reserve” gross vehicle weight (GVW) when initially spec’ing a truck. Generally speaking, a vehicle should have 15- to 20-percent reserve GVW. For example, for a 5,000-lb. maximum payload estimate, spec a vehicle to carry a payload between 5,750 to 6,000 lbs. Reserve GVW will allow a truck to perform its intended job with less downtime and with greater safety. Overloading is Like a Cancer
Federal, state, and local regulations govern the weight of commercial vehicles. These regulations address GVW, gross combination weight, tire load, and axle weight. The weight must be balanced properly so that one axle or a set of axles are not overloaded. One practical tip on how to determine actual payload is to have the truck loaded as it would be in a normal workday and have the trucked weighed. While doing so, also have the front and rear axles weighed. This will let you know whether you are overloading the whole truck or just one of the axles. A vehicle can be under GVW, but still be overloaded on one of the axles, resulting in excessive wear-and tear on tires and suspension. Lastly, do not modify a vehicle to accommodate a heavier payload, such as changing tire sizes, adding spring kits, air shocks, heavy-duty brakes, and anti-sway kits. When you modify a vehicle, you create an unsafe situation by changing the integrity of the vehicle. This may also affect the new-vehicle warranty and increase liability exposure if there is an accident. Overloading is like cancer. It often goes unnoticed until it is too late to do something about it. Let me know what you think. mike.antich@bobit.com