LONGS CREEK, N.B. – There are no mainline weigh-in-motion (WIM) scales in Canada used directly for truck weight enforcement, but that’s all about to change.

Both New Brunswick and B.C. are installing – or at least planning to – install such scales while elsewhere in Canada, most WIMs have been abandoned due to maintenance problems.

Embedded in the pavement a mile or so before an inspection station, WIM scales are widely used in the U.S. to screen trucks on the highway to help determine which ones have to report to the inspectors. According to Brian Taylor, of International Road Dynamics (IRD) in Saskatoon, Sask., there are probably 175 mainline WIMs south of the border currently used to screen truck traffic.

IRD makes and installs many of these scales and is also working with B.C. and New Brunswick on Port Mann and Longs Creek projects respectively.

Taylor, who co-authored a report on the WIMs together with Derek Trishuk and Curtis Berthelot of the University of Saskatchewan, thinks the mechanisms are well worth the approximate US$750,000 installation cost when used to sort trucks on the highway.

That, at least, is the conclusion of the paper they presented to the Transportation Research Board in Washington, D.C. last January. (Actual construction costs vary widely from one site to another depending on how much pavement work has to be done and how many other devices are installed with the WIM.)

“The improvements in weight enforcement efficiency translate into considerable savings for both the weight enforcement agency in terms of improved enforcement effectiveness and protection of the infrastructure, and the trucking industry in terms of reduced user delay costs,” according to Taylor and his co-authors. They base their views on a calculation that shows the benefits of a mainline, pre-screening WIM are in the range of 44 to 93 times higher than the cost of installation.

Installation costs include the scale itself, plus the necessary peripheral equipment needed to make the whole thing work. This can either be roadside signs sending “Report to Scale” messages, or a system based on transponders in the truck cabs, which are read by a scale house computer.

A benefit-cost ratio of 44 to 93 is an awfully big number. It suggests an enforcement agency would be foolish not to grab the telephone and order a WIM system for every one of its stations.

There are, however, problems.

While the savings sound very high, all costs are borne by the enforcement agency (in many cases the jurisdiction’s department of highways) and most of the benefits are enjoyed by the trucking industry. Unless there is some way to funnel the benefits back into the budgets of the enforcement agency, it’s difficult to convince those who control the purse strings to part with more than $1 million Canadian dollars.

Heavy Vehicle Electronic License Plate (HELP) Inc., of the U.S., has found a way to do this. Every time a truck is cleared to bypass an inspection station, the operator pays a fee of 99 cents. HELP uses its PrePass transponder to do this and currently, there are 200 weigh scales in 24 states equipped to interface with these mobile beacons. Some HELP sites only check credentials – for example, IFTA and IRP registration – and safety records; others also use WIM to sort out the trucks allowed to bypass. There are 204,000 trucks equipped with PrePass transponders.

The Longs Creek station in New Brunswick will rely on bilingual highway signs to tell truckers if they need to report to the scale. The Port Mann facility on the other hand will be a part of the North American Pre-clearance and Safety System (NORPASS) – a competitor to HELP’s PrePass. NORPASS uses transponders to flash red or green lights at the driver indicating pull over or bypass situations.

Unlike PrePass, NORPASS does not charge a fee for this luxury yet there are probably less than 20,000 trucks with these transponders.

The second problem with the estimate of a cost-benefit ratio in the range of 44 to 93 is it is calculated on the basis of an average of five minutes for every truck required to stop at a scale multiplied by a value of $1/minute. In other words, Taylor and his co-authors assume the time saved by a truck for not reporting is worth five American greenbacks. Maybe a figure in line with PrePass’ charge of 99 cents would be closer to the mark. This would reduce the benefit-cost ratio to roughly one-fifth the number calculated in the research paper.

But even with a lower ratio, mainline WIMs used for bypassing still seem to make sense as benefits outweigh costs. It’s odd, then, that most WIMs installed in Canada are not used for this purpose or, more generally, have been abandoned altogether. Ontario has several WIMs that are not being used along Hwy. 401. These were installed when the province conducted a pilot project known as AVION in the 1990s. This was a part of the U.S. bypass program originally known as Advantage I-75, but it has since folded into NORPASS.

Other provinces have used WIM to sort trucks on the entrance ramps to weigh scales. And some provinces like Manitoba use WIM on selected spots of main highways to collect information on truck axle weights and pavement loads.

But this information is not used directly for enforcement purposes. Other provinces (Alberta, Newfoundland and B.C.) have installed WIMs in the past but have since given up on them.

So why, if mainline WIM makes such sense as an enforcement tool, are so few provinces lining up at IRD’s door with their orders?

One problem is clearly budgets and the fact Canada doesn’t have a system of charging those carriers who want to bypass for the cost of the system.

As well, the broader problem may be the fact many roads in Canada don’t have the truck volumes found in the U.S. (Ontario’s 401 and a few other spots are obvious exceptions). Expensive bypassing technology only makes sense when there are lots of trucks – probably more than 200 an hour.

Additionally, over the last decade many provinces – particularly Ontario – have changed their enforcement emphasis somewhat. Ensuring legal weights is still important, but safety checks (CVSA) are even more important.

WIM by itself can’t sort out the “high risk” truckers from the “low risk” ones. To do this, you have to use a system incorporating transponders on the truck and the ability to exchange safety rating information among the provinces. Although the provinces are struggling to put some type of safety data exchange in place, it will be some time before a nation-wide system is working.

In the U.S., by contrast, it is the federal Department of Transportation that produces measures of a carrier’s safety performance and this information is freely available to anyone, including those enforcement officers deciding who should bypass.