Roadside truck inspections have become almost hallowed ground for enforcement agencies across the country. The effectiveness of these programs in improving safety have never actually been put to a rigorous test yet enforcement agencies in every province believe their inspection programs are necessary. They may well consider some of the research surfacing south of the border.

The relationship between inspections and highway safety is complex but new research conducted in the U.S. is casting doubt on the impact roadside inspections actually have on improving safety. The results from the latest study, by Piyushimita Thakuriah and three others from the University of Illinois in Chicago, were recently presented to the Transportation Research Board. They raise serious questions about the wisdom of the millions of dollars the U.S. Department of Transportation spends assisting states with inspection programs. This is the second time a major U.S. study has raised such concerns. An earlier one in 1994 from Northwestern University, also in Chicago, concluded that the benefits of the inspections barely exceeded the cost of the program.

Thakuriah’s study shows that when you compare the almost one million trucks Illinois inspected between 1993 and 1998, there is no statistical difference in collision rates between those which were inspected and found to have an out-of-service violation and those which were inspected and given a clean bill of health.

An out-of-service (OOS) violation can be either for the vehicle – for example, brakes out of adjustment – or it can be for the driver – for example, a driver over hours on the logbook. Inspections are done on commercial trucks (in Canada, a truck with a registered weight over 4,500 kilograms) and buses.

The thinking behind the Illinois study is that carriers allowing trucks out on the highway with mechanical defects or allowing drivers to operate in violation of some regulation are inherently less safe than carriers that make sure all the regulations are followed. Therefore, one expects trucks with any type of OOS violation will tend to be in more collisions than other trucks. To test this, the Illinois researchers divided trucks into two groups-those that had OOS violations and those that didn’t. They then linked this information with collision statistics for one year after the inspection date. They concluded: “This shows no evidence that the expected number of crashes in which vehicles incurring zero violations are involved is different from the expected number in which vehicles incurring one or more violations are involved.” The full results are a little more complex as they did find that trucks with a great number of OOS violations (over 14) during an inspection – these are obviously the old clunkers- do have a higher chance of being involved in collisions.

But the main finding that, in general, there is no difference in collision rates between trucks that do or do not have OOS violations during an inspection, raises an interesting question. Why are inspectors stopping so many trucks? In the United States, about two million trucks are stopped every year for an inspection that takes up to a half an hour or longer. No national figures are available in Canada, but most provinces take a fairly vigorous approach to inspections. Ontario, for example, has a goal of 40,000 trucks a year. While there is no research on this subject in Canada, enforcement agencies believe that inspections do have a positive impact on safety. If we didn’t inspect trucks, the argument goes, there would be all kinds of junk on the road – trucks just waiting for an accident to happen.

This University of Illinois study does not go on to suggest that inspections are a waste of time. The authors leave to others the job of figuring out what all their numbers mean for enforcement programs. But Leon Moses and Ian Savage, from Northwestern University, were bolder in their 1994 study. They suggested governments would be smarter if they spent less money on inspections and more on other safety programs.

Moses and Savage calculate that, in 1992, it cost governments over $60 million to run the inspection program. Add to this the cost carriers incur when they are stopped and the downtime it takes to fix an OOS violation and the total cost of having an inspection program is over $174 million. And the benefits? They estimate that by putting a truck OOS for a mechanical defect reduces the collision rate for these trucks by 8-13 per cent. Putting a driver OOS reduces the collision rate by 3-4.3 per cent. Using information on the average cost of a collision, they then calculate that collision costs in the U.S. are $114-$195 million lower than they would be if the roadside inspection program didn’t exist. The hard part, however, is to calculate what the deterrence effect is. That is, because everyone knows that their truck might be inspected, trucks and drivers are possibly in better shape than they ordinarily would be. Depending on the assumptions made, Moses and Savage calculate that the benefits of the program just might exceed the costs under the most favourable conditions. But under less favourable assumptions, they might not.

One factor accounting for the findings of both the University of Illinois study and the earlier research by Moses and Savage is that mechanical defects are not usually a contributing factor in truck collisions. So stopping trucks and finding OOS defects is not necessarily going to have a big impact on collision rates. The latest figures from Ontario for 1997 show that “vehicle defect” is listed as a contributing factor in only one per cent of tractor-trailer collisions. True, a policeman investigating an accident may not always spot mechanical defects. Other studies have suggested that mechanical defects may play a larger role in truck collisions. A 1997 study from the Ecole Polytechnique in Qubec made a detailed investigation of 195 heavy vehicle accidents and found that 13.2 per cent were wholly or partially attributable to mechanical defects – mainly malfunctioning brakes. Most of these brake problems could have been caught by the driver during a thorough pre-trip inspection-or, of course, by an enforcement officer during an inspection.

But, whatever the number, there are still relatively few collisions caused by mechanical defects.

Similarly, driver condition (fatigue, drugs, alcohol) is rarely listed as a factor in a truck collision. So catching a driver who is OOS also isn’t necessarily going to have a big impact on safety.

So are roadside inspection programs accomplishing anything? Interestingly, a couple of other studies from the U.S.-both funded by the U.S. Department of Transportation-suggest that the answer is “yes, they do make highways safer.”

In 1992 Michael Lentz and Christopher Allanach published a paper that looked at truck accident rates in 13 states over a two year period-in the mid 1980s, just after the U.S. federal government started pumping money into the states to support their roadside inspection programs. And guess what they found? Truck collision rates declined significantly. Lentz and Allanach attribute the decline to the inspection program.

A more recent study (1998) by Don Wright and Dave Madsen from the Volpe National Transportation Systems Center in Cambridge Massachusetts, and Tom Corsi from the University of Maryland, uses 1996 information on the approximately two million trucks inspected in the U.S. Of these two million trucks, 437,478 had OOS vehicle defects and 161,530 had OOS drivers. The study suggests that 4.6 per centof truck crashes have vehicle defects as a contributing factor and 5.7 per cent have driver problems as a contributing factor. The authors of the study assume that a truck put OOS has its mechanical problem fixed for three months (or 15,000 miles) after the inspection and that a driver put OOS has two months (or 10,000 miles) of accident-free driving because of the inspection. On the basis of these accident-free miles of driving, they calculate $47 million in reduced collision costs in the U.S. They also calculate a $
39 million annual reduction in collision costs because of the deterrence effect. A combined savings of $86 million annually seems to suggest that roadside inspections are well worth the effort.

While there are no relevant studies from Canada, you can bet that every enforcement officer in the country is looking at the declining collision rate for trucks and taking some of the credit. And maybe they should. The number of trucks involved in collisions has been steadily declining since 1989, even though total truck travel has been increasing. And the total number of fatalities on the road in 1998 was at its lowest level in 43 years in Canada.

Although there is no statistical evidence in Canada to link roadside inspections with collision rates, it clearly would be very difficult for any province to cut back on its roadside inspection program just to see what would happen to safety. Like it or not, roadside inspections are here to stay. But, as the Canadian Trucking Alliance argues, maybe what is needed is a critical re-think of the factors used to put a truck out of service. All North American jurisdictions use uniform criteria (CVSA) to determine when a vehicle should be put OOS and the original idea was that these should be defects that make it unsafe to operate on the road. It’s not clear, though, that there is much scientific evidence backing up the criteria used with actual on-road collision information.