There are certainly a lot of regulatory issues in trucking at the moment. Some are new and others have become a continuing saga – such as the hours of service. The issue of speed limiters is interesting in that a trucking advocacy group (the ATA) came out in favor of them before the government had really expressed a firm opinion. Parts of Canada have required them for several years and yet the dire predictions of the opponents have failed to materialize.

Trucks have always had a limiter of sorts – the engine governor. That device isn't set to a particular speed but rather a maximum engine rpm thus protecting the engine from damage and excessive wear. On the other hand, a speed limiter acts to limit top speed, regardless of engine rpm. Most trucks operating today simply need a change to the truck's computer system to limit top speed. From an equipment standpoint it's a pretty simple operation, but it has plenty of proponents and opponents. They all agree on one thing, speed limiters affect safety. The key question is: does this increase safety or result in unsafe operating conditions?

In reality, we're really not talking about limiting a truck's top speed, since all trucks have a maximum, even if the engine governor determines it. This discussion is really about what that speed should be. And if you really want to boil this all down, it's about a national speed limit for trucks. Opponents point out that it will result in a speed differential between trucks and cars.

The Comprehensive Truck Size and Weight study published in 2000 does conclude that speed differentials do have a negative impact on safety. However, that information is contained in a section of the study dealing with trucks ascending long grades. This results in a very large speed differential as compared to the more common 5 – 10 mph in those states that have two speed limits. For many years Ohio was a speed differential state and yet there's no hard evidence that truckers going through Ohio were more likely to be involved in a crash. In fact, when the Ohio turnpike increased its speed limit for trucks crashes actually increased 5%.

Various studies in the U.S. and abroad have shown a clear relationship between speed and crashes. There are two areas of concern: the risk of a crash and the severity of a crash. Consider these statistics:

--- When the national 55 mph speed limit was adopted: fatalities declined 16%
--- Fatalities immediately climbed when congress allowed states to set their own limits

The use of studies is always controversial. It's not that the data itself is flawed, but the collection methodology and data interpretation can always be called into question. Recently the Federal Motor Carrier Safety Administration released a study that analyzed data from 20 trucking companies over a three year period. The crash rate was 50% higher (16.4 vs. 11.0 per 100 trucks) for trucks not equipped with a speed limiter. Shortly after the release of the study one of the researchers stated that he disagrees with the conclusion that speed limiters are beneficial. He plans to publish a rebuttal and has asked that his name be removed from the study.

Other countries have already taken this step and have concluded that there are safety benefits. If we wait for the one “definitive” study that will positively demonstrate the benefits then we'll never take action. The ATA has taken a bold step and their initiative is worthy of support. You don't need a study to know that ever increasing speeds make it more difficult to react to traffic changes, decreases maneuverability and increases stopping distance. In case of a collision, the higher the speed the more severe the collision.

This is a good idea whose time has come. The cost is negligible, the savings (human) are tangible. It would be a mistake to oppose this idea and to insist that trucks must go faster to make money. The industry should take the high ground and endorse 65 mph speed limiters.