Haul trucks are off-road, heavy-duty dump trucks specifically engineered for use in high-production mining and exceptionally demanding construction environments. Most are dual axle; at least two examples of tri-axles were made in the 1970s. Haul trucks are denominated by their payload capacity, by weight (variously in tons, tonnes, and kg).

Most haul trucks have a two-axle design, but two well-known models from the 1970s, the 350T Terex Titan and 235T WABCO 3200/B, had three axles. ^[2] Haul truck capacities range from 40 short tons (36.3 t; 35.7 long tons) to nearly 500 short tons (454 t; 446 long tons).

An example on the smaller end is the Caterpillar 775 (rated at 70 short tons [62 long tons]).^[3] Quarry operations (which produce payloads that have value) are typically employ smaller trucks^[why?] than mining operations (such as removing undesirable overburden, an expense).^{[citation needed]}

Haul trucks can generally be distinguished from standard dump trucks by:

• Being far too large to travel legally on public roads
• Having a dump body made of exceptionally strong steel plate that extends over the cab to protect it, angled upright at its end (or entirely) to aid in dumping; some are heated by exhaust gases to prevent loads from sticking or freezing to the bed;
• Having a driver's cab narrower than its body;
• No axle suspension;
• Limited speed and operating range;
• Special off-road only tires;
• A ratio of dead weight to payload not exceeding 1:1.6^{[citation needed]}

Most large haul trucks use some form of traction motors coupled to regenerative brakings for power, braking, or both.

Haul trucks are classified by:

• Type of unloading (dump or rear-eject);
• Direction of discharge (side, rear);
• Type of body (hopper, platform, sliding hopper, sliding platform).

The largest, highest-payload-capacity haul trucks are referred to as ultra class trucks. The ultra class includes all haul trucks with a payload capacity of 300 short tons (270 long tons) or greater.^[4] As of October 2013^[update], the BelAZ 75710 has the highest payload capacity, 450 metric tons (440 long tons; 500 short tons).^[5]

A rear-eject configuration is an alternative haul truck body style. Instead of lifting the bed vertically, the hydraulic cylinder pushes a ram-face horizontally through the body to eject the hauled load.^[6]

Rear-eject dump vehicles were first introduced in the 1980s by LeRoy Hagenbuch, P.E. of Philippi-Hagenbuch, Inc.,^[7] for a refuse hauling application in New York City. They were designed to work on Volvo BM truck chassis. While the functionality of the ejector bodies worked well, they were prone to maintenance issues and were not replicated until the 1990s.^{[citation needed]} The next documented ejector bodies were developed by DDT, a UK truck manufacturer.^[8] A variation using steel chains instead of a hydraulic ram was introduced by Bell, but did not become popular.^[9]

Caterpillar Inc. began offering a rear-eject option using technology originally designed for its scrapers after one of its contractors successfully converted a few CAT D400 models. The new design, installed on the company's D400E model, was less likely to jam in cold weather.^[9] CAT later began manufacturing a standard R.E. body for its 730, 740, and 740B articulating haul-truck series.^[10]

Philippi-Hagenbuch, a company specializing in truck body design, developed its own mechanism for its rear-eject bodies, and has patented its design in the US, Europe, and Australia.^[6] The company customizes Rear-Eject bodies or trailers for several manufacturers' off-highway vehicles; including both rigid and articulating varieties.^[11]

As of 2014 Caterpillar Inc. and Philippi-Hagenbuch, Inc. are continuing to manufacture Rear-Eject bodies for off-highway applications,^[6] each using its own design of mechanism.

Pros and cons

There are both advantages and disadvantages to a rear-eject truck:

Pros

• Because rear-eject bodies do not lift, or move externally in any way, they maintain a lower center of gravity. This means more stability on uneven terrain where the truck might tip over during the dump process.

• The truck can also be driven while dumping is in progress; this reduces subsequent time and effort spent on grading the dumped material.^[12]

• Rear ejects are typically better suited to completely eject sticky material, preventing "carry-back."^[9]

• A rear-eject truck can deliver a load in an area with a low overhead barrier.^[13]

Cons

This section needs expansion with: disadvantages of rear-eject versus end-dump trucks. You can help by adding to it. (February 2024)

Look up long haul in Wiktionary, the free dictionary.

• Articulated hauler
• Dumper
• Haul road
• Rear-eject haul truck bodies
• Unit Rig