Why is it that dump trucks are consistently the slowest vehicles on the road? They linger a bit longer at traffic lights, accelerate slower, cruise at lower speeds, and take longer to stop. I don’t think it’s a weight issue because semi’s haul just as much, if not more, weight and they are not as slow. My theory is that dump truck transmissions are geared more for off-road use (by that I mean operating around construction sites and the like) than a semi, which is geared for cruising on open highways. Any truck drivers that can give some insight?
A trucking question! I love these.
No, it’s mostly weight. Gravel, sand, and other aggregate loads are the heaviest commonly carried loads on trucks, by far. Dump trucks are carrying FAR more weight by volume and per axle than most semis. Most semi loads are comparatively low weight loads; stuff like furniture and consumer goods tends to “bulk out,” fill the trailer’s volume limit, before it gets particularly heavy.
Dump trucks are carrying more weight per axle than any other kind of truck, vastly increasing friction, and even the small straight dumps often have higher weights even than full sized tractor-trailer units. The smaller straight dumps also tend to have less engine power than the big highway semis, since they’re built for local work, not long haul highway driving.
However, your observation about the gearbox setups is part of the story too. Dump trucks do tend to have lower gear ratios and, you may notice, bigger wheels and tires.
Because they’re big. And heavy.
Because anything that started out slower than a dump truck is now just a greasy spot.
I think they’re also geared for shorter hauls. While many semis are built for interstate commerce, dump trucks usually operate over much shorter distances. I doubt a “highway” gear is a standard feature.
C’Mon guys!
They are government employees or they are being paid by the hour.
Head to Winter Garden, Florida, a blue-collar suburb of Orlando. You’ll never see as many dump trucks on the road as you will see in Winter Garden. Loaded, they’re slow as molasses. However, on the return trip, they’re quite fast. Winter Garden supposedly has lots of problems associated with the heavy dump truck traffic in town; battered roads, lots of traffic fatalities, traffic violations by dump truck drivers (they get paid by the load, so they often blow past red lights and stop signs), and its contribution to an already-bad image that makes the town unattractive for more upmarket development.
Okay, now I’m curious. How much weight are we talking about here? Are the legal weight limits the same for dump trucks as they are for semis (75,000 lbs. gross, IIRC) ?
Since we’ve seen a number of good answers to the OP’s question… do those same answers apply to garbage trucks?
I got stuck behind one on my commute to work, and it seemed to be going precisely 35 MPH on the Interstate.
A couple more things make a dump truck tricky. One is the number of wheels. The big double axle rigs only have ten tires on the road. Some have an extra axle for weigh stations, but normally they don’t touch. The other thing is that the load is carried very high. A driver could work at it and go faster, but nothing he can do will make it stop any quicker. If he has to make a sudden swerve, the high load is likely to fall over. It’s not really uncommon to see a big stone truck on its side.
Depends on the truck. The big belly dumpers routinely gross 125,000 to 130,000 pounds with two trailers. I’ve seen companies get short haul permits for triple trailers and 145,000 gross. Single trailers probably run 80,000 to 90,000 pounds max, but it seems to me I’ve seen a case or two with a single big dumper running just over 100,000.
Legal weight is determinate on the number of axles and their configuration. The maximum possible weight is pretty high, but weights and allowable configurations vary from state to state and province to province. IIRC, the province of Ontario has the highest allowed weights; I think California has the lowest and the most restrictive configuration limits.
Technically, the weight laws are almost always the same for all cargoes on the same configuration, except in special circumstances.
The really key laws are AXLE weights. A truck that has a perfectly legal gross weight can be way, way over on one axle, which is why loading and distribution is so important.
Dump trucks invariably push the legal weight limits for their configuration. Every one I’ve seen could be very easily overloaded.
Well, as somebody who has driven these vehicles, I can say that they are built perfectly for a purpose-moving heavy loads over short distances.
Many dump trucks serve yard time only. If you buy offroad diesel you make sure of that.
The vast majority of dump trucks serve local duty only. There are very few commodities that are profitable to be shipped long distances and sold for dollars on the yard.
Dump trucks that carry waste materials for disposal carry them as short a distance as possible to the nearest cost efficient disposal area.
Fully loaded, any dump truck will be going extra slow. Go around it as safely as possible. Give these vehicles extra room to enter and exit the highway. At on/off ramps give these vehicles the right-of-way.