VANCOUVER, B.C. – An increase in forest road grades along B.C.’s coast has raised eyebrows and drawn concern for the truckers descending the off-road paths.
The Forest Engineering Research Institute of Canada (FERIC) undertook a study in an attempt to develop guidelines for the safe descent of steep logging roads under several operating conditions.
“There were a lot of safety concerns. There were one or two fatalities on the coast due to steep grades; they were runaways due to the steep grades and failure of brakes,” noted Seamus Parker, senior researcher with FERIC Transportation Group. “At about the same time we had already started the study, but that pushed it along even more.”
The study began in 2003. After three years of testing and analyzing data, FERIC published its report this spring.
“It’s ongoing but that phase of the study was the coastal off-highway portion,” noted Parker. “It was dealing with fat trucks – which are called as such due to the base of the truck being 12 feet wide.”
The first portion of the study involved field testing, where FERIC installed instrumentation on a coastal off-highway truck – a Pacific P-16. The instrumentation was in place for three months and measured braking energy requirements on steep grade descents.
“There was one test truck where all the instrumentation was installed, but we tested other trucks to get stopping distances and brake temperatures,” Parker told Truck West. “What we used to determine if you could safely descend a grade was, if the driveline was to fail could you safely come to a stop with the emergency brakes?”
Many of the guidelines developed in the report focus on risk assessment for planners, which will aid them in determining maximum loads and posted speed limits along certain routes.
The report also included some safety practices for the truck operators, with the main factors being traction, truck speed and brake adjustment.
“Every little bit helps when going down the grades,” commented Parker. “If you’re on loose material all the brakes in the world won’t help you.”
Solid traction was one of the main factors in determining speed on a particular grade, but the time of year plays into a road’s operability as well.
“These trucks generally suspend operation in the winter, but in the spring it can be quite slippery,” said Parker. “In those situations you shouldn’t go down anything more than 20% to 22%. In the summer with more compact gravel on the roads you can go up to 28%.”
Traction can be a very situational factor. Parker noted that the length of the grade and switchbacks have to be taken into account when determining how to handle the grade.
“A driver can get a sense of the traction going uphill and it will give you an idea of what will work on the way down; and they can assess the situation with the loader,” he explained.
The brakes play an integral part in keeping a truck in control while descending the steep grades and it’s important for drivers to constantly monitor the brake system.
“Another critical part is for truckers to monitor brake adjustment,” said Parker. “All these trucks have manual slack adjusters and they need to keep them monitored.”
In maintaining the proper speed to safely handle the off-highway routes, the report indicates selecting the proper gear is key.
“It takes about five seconds to realize you’ve lost the driveline,” explained Parker. “So they need to select a fairly low gear, but not so low you’re revving too high.”
Parker explained the best way to determine the appropriate gear for a particular route comes with experience.
“Many drivers will keep running on the same routes, so when they start they should maybe use a three-quarter load until they are used to the route and know the gear for that particular haul road,” he noted. “Then when they’re comfortable they can increase to a full load.”
Stability can also play a factor in a truck’s ability to maintain control while descending steep grades.
The off-road trucks can stack loads fairly high, but Parker warned of stacking loads too tall; and suggested drivers keep their loads under 21 feet for optimum stability.
While the truck driver is the final factor in ensuring the coastal off-highway trucks are operated in a safe and effective manner, FERIC hopes the report can guide the planners and make the driver’s job easier.
“The guidelines for the planners aim to make it simpler for the drivers to handle differing grades through posted speeds,” concluded Parker.