Yesterday morning, a dump truck operator managed to hit the “dump” button while traveling at freeway speed between San Francisco and Sacramento - posted as 55 mph for trucks, but trucks always seem to be doing 65. Operator claimed they were trying to set the cruise control, but hit the wrong button and dumped twelve tons of gravel on the interstate.
No mention was made of the presumably serious damage to any cars that were behind him getting hit by twelve tons of gravel.
My question is: Why is the dump control “live” and active when the truck is moving at roughly 60 miles per hour? I can understand being able to dump when moving at perhaps 5 mph to lay out the load in a long pile rather than a huge heap. Was this a case of stupid design or a failed interlock?
Depends on the truck. An “end dump” is not designed to dump its load at higher speeds. It’s also not as easy to do as with a “belly dump”.
An end dump is designed primarily to leave a large pile of earth or rock. A belly dump is used to spread material at a uniform depth over an extended surface area.
Belly dumps typically can move at relatively higher speeds while performing this work.
There’s a surprising number of situations when you want to spread something on a road while moving fast. E.g., a lot of “chip rock” surfacing is done quickly. (Some tar is sprayed on the road, then the dump truck runs down the road spreading a thin layer of gravel. It’s a very cheap method so “time is money” to the contractors.)
Sanding of roads can also be done at highway speeds by dump trucks in areas where “official” sanding trucks are not worthwhile due to rare poor weather.
Probably because the cost to develop and build such a safety interlock would cost more than the rather rare accidental dumping of a load. Rather than paying a few hundred dollars more for a dump truck with such an interlock, construction companies might just prefer hiring smarter drivers. So there is no market for such an item.
P.S. Have you looked at the dump control on trucks? Often it’s little more than a hunk of rope connected to a hook that latches the tailgate. What kind of a “safety interlock” would you suggest for that?
Yah, definitely need smarter drivers, if that’s the case - driving down the highway and tugging a rope, expecting it to set the cruise control. Seriously, though, if a truck is using rope to activate the dump, would that rope be running into the cab, or just dangling in back so the operator desn’t have to jump up to reach the lever? And would such a “Beverly Hillbillies”-esque truck with ropes running into the cab be highway-legal?
This truck had cruise control, so I’m assuming at least a moderate level of sophistication. What wasn’t described in the news report (and there weren’t any photos) was if the driver managed to open just the hatch in the tailgate, the entire tailgate, or engage the hydraulics to raise the bed.
A little more information for you: The “rope dangling down” is connected to a release lever that allows the tailgate to open. The dump bed can only be raised by engaging the PTO in the cab, which is a conscious effort on the part of the driver. There is virtually NO way that he is going to mistake the PTO knob for the cruise control. There is also NO way that he is going to mistake a piece of rope for a cruise control button. The rope doesn’t go into the cab, it merely makes the lever reachable for the driver without exiting the vehicle.
I’m still betting that the truck in question was a belly dump, which has a completely different operating system.
