Do Different Speed Limits for Trucks and Cars Make Roads Safer?

Being a third-party logistics (3PL) provider, Legion Logistics is very interested in the nation’s interstates, including safety measures and whether or not they are effective. Several years back, many states had speed limit signs along their highways that had two different speeds – one for cars and one for trucks. The truck speed limit was usually 10 miles less than the car speed limit. Nowadays, these signs are a little harder to find since only eight states currently have split speed limits, and one of those states is trying to decide if it is worthwhile.

Wayne State University researchers in Detroit, Michigan have been given the task of studying whether or not Michigan should continue to use split speed limits. In theory, trucks take longer to stop because they are so much heavier than cars or SUVs, so they should be going slower in case there is a sudden need for them to stop. This thought is what made split speed limits popular in the 1960s.

However, now that they have been in use for a while, other concerns are being raised. The main argument against split speed limits is that the gap in speed is actually more dangerous. Slower trucks have more passenger-car drivers passing them, and changing lanes often leads to accidents. Also, if the speed limit for cars is already 10 miles higher and drivers exceed it by a few miles, they could come up very quickly on a truck and have to slow down dramatically. Every driver has experienced a braking chain reaction that occurs on highways; it can be scary and downright dangerous.

Multiple studies have been done on the issue and the results are mixed. In 2005, the Federal Highway Administration (FHA) reviewed studies done by different groups and concluded that the benefit or detriment of split speed limits seems to be place-specific. Officials in Idaho recently decided to maintain different speeds based on their research, while Illinois, Ohio, Texas and Virginia have made their speed limits the same in the last few years. The Michigan study is expected to be complete in 2014.