Between 1986 and 2004 the Ontario mining industry reported seven fatalities and 73 lost-time injuries as a result of poor line of sight visibility from load haul dump (LHD) vehicle operators.
LHD machines are electric or diesel powered trackless vehicles with a scoop or bucket on the front. They are primarily used to transport ore from the production face to dumping points.
Over the last 20 years, the use of LHDs in mining has increased. Improved mine engineering and a better ground support have substantially reduced many of the historical mining hazards, according to a report authored by Jonathan Tyson titled To See or Not To See ... That is The Question.
However, the introduction of mechanized equipment has brought on new hazards, specifically visibility issues pertaining to the LHD operator’s line of sight. Based on international reports, much of that equipment has been designed in such a way that inadvertently increases the probability of human error.
In 1999, Dr. Tammy Eger, an assistant professor with the School of Human Kinetics at Laurentian University, performed a series of field tests using a light bulb placed in the cab of an LHD. The bulb represented the operator’s eye, and the light from it illuminated what is visible from the cab. The experiment confirmed that an operator’s line-of-sight was significantly obstructed. The experiment could be expanded to apply to any type of heavy equipment such as dump trucks, backhoes, front-end loaders or cranes.
To understand the vision impairment in greater detail, Eger and Laurentian mining technology chair, Dr. Paul Dunn, took the project into cyberspace. A “box plot” was created using Jack 4.1, a software package which could model the mining environment. Eger could scale in any size human to represent the operator, and various LHD designs were incorporated, along with a training module comprised of a gaming engine. The module allows the user to become the LHD operator.
“You can sit in the cab and actually drive the LHD around,” Dunn says. “You can see the visibility profile as you drive around the mine.”
The module is able to incorporate new equipment designs, so LHD manufacturers can scale in older models against the newer design versions and see the difference in visibility. In fact, manufacturing companies have given Eger and Dunn new LHD blueprints to use in the module for feedback.
“A complete redesign of the LHD vehicle is not going to be possible given the environment it has to work in,” Eger says.
“(But) visually (users) can obtain a very quick feel for what can happen if you make slight changes in the design.”
The Mines and Aggregates Safety and Health Association (MASHA) is using the training program to prepare vehicle operators for working in drifts.
Dunn says visibility underground varies from mine to mine, so he performed another field study using a laser scanner located on the seat of an LHD. A Mensi GS100 laser scanner works on the principle of time-of-flight. The scanner’s pulsed, visible green beam moves across its target.
The horizontal and vertical angles of the beam and the return time-of-flight of the reflected pulses are measured for each point. From the time of flight, a measurement of distance is also generated. Together, these measurements produce an “impact location,” which is called a cloud of points.
“If the beams hit a cab post, then you know that was a blockage,” Dunn says. “You could identify light brackets that were affecting the visibility then propose modifications to it.”
Both methods are very usable for the industry depending on what type of application they want it for, Eger says.
