Emergency Escape Facilities
Driving a heavily loaded coal truck down a steep graded haul road is the work assignment for many of the nations miners each day. This is one of the most hazardous occupations in the coal mining industry. Loosing control of a loaded truck on steep grades has caused many fatal injuries.
Failure to maintain trucks in safe operating condition and inadequate training are usually contributing factors to loosing control of a truck on a steep grade. The industry has taken great steps to eliminate these two factors in a effort to prevent these type of injuries. However, because of the intricate design of these type of trucks and the extended exposure of the drivers, accidents still occur.
These trucks normally descend steep grades at slow speed using the engine brake in conjunction with the service brakes to control the truck. Failure of the brake system or driver error ( getting the transmission out of gear ) can cause loss of control. If when this occurs, the driver is provided with a run off ramp or barrier to immediately steer the truck into, injury of the driver is likely to be prevented. In most cases damage to the truck is also minimal.
Emergency escape ramps work well if they are designed so as to allow the run away truck to get into the ramp, align with the speed retarding medium, and the medium is such that the truck is brought to a stop gradually. These ramps require a lot of area to construct and if used are usually not located often enough to be immediately available at all times the truck is traveling the steep grade.
A type of emergency facility that has been successful on mine haul roads and is usually more feasible to provide where permit problems and road width are issues is a series of short barriers, one located after the other continuously down the steep grade. The barriers are made out of course material with some fines intermixed to give them a strong consistency that will cause them to provide good resistance to the truck undercarriage. This consistency also allows for the barriers to be constructed with less height and width. They are usually approximately 60 ft. long and separated at least 100 ft. to allow the run away truck to get centered up before entering the barrier.
These type of barriers are designed to stop a run away truck before it increases speed, so they have to be provided continuously down the steep grade to be effective. They are typically 3 ft. high and 3 ft. wide at the top and take up approx. 6 ft. of road width. The driver has to steer the truck into a barrier immediately when it breaks loose for the barriers to work effectively.
The picture depicted here shows a recent save of a loaded run away truck at a coal mine. The company voluntarily provided barriers on steep grades of their roadways August, 1999. The driver of the truck lost control in April, 2000 and used the barrier to stop the truck. He was not injured and the truck was not extensively damaged.