A loaded logging truck began descending a short spur off the landing to the mainline. The spur was only 80m long with a switchback mid-way but had up to 20cm of mud (on a firm base) from recent heavy rains. The lower 40m of the spur was a 20% grade.
An earlier truck had encountered no problems with the muddy spur but the subject truck had required a tow up the short road and also had to be towed a short distance to get started once loaded.
The driver of the loaded truck had over 30 years safe driving experience in logging trucks on local roads and did not consider the short spur to be unsafe or any different than other muddy spurs. As he proceeded down the grade, he could feel that the axle converter was not working properly; it was actually crooked and not tracking straight and the trailer was not following the tractor around the curve.
In the past, this situation was always remedied by speeding up slightly in order to pull the axle converter straight. However, in this instance, it is thought that the slippery condition of the road did not allow the axle converter to straighten out and it continued to force the trailer to the right and over a shallow bank. The trailer eventually pulled the tractor unit over on its side where it sustained considerable damage. The driver was wearing his seatbelt and was not injured.
• In periods of inclement weather, such as heavy rain, road conditions can change rapidly depending on the soil type. Drivers must continually be aware of changing conditions that could affect their safety. Not all mud is the same!
• Drivers should identify marginal conditions, such as muddy, steep grades, and err on the side of caution by taking advantage of equipment that is available to help them out.
• Be aware that, under marginal conditions, some equipment (such as axle converters) might not work as planned; all equipment has limitations.
• Landing crews should observe and assess conditions to the extent possible. They can advise other users of the road that conditions are changing and make suggestions to drivers of possible assistance.
• Be familiar with the RADAR concept to understand the process to follow when confronted with unusual situations.
For more information: Rick Johnson, RPF - Pilot Point Forest Consultants 250-365-9983
|Muddy road, axle converter issues send log truck into ditch.pdf|