A "transfer dump" is a standard dump truck which pulls a separate trailer which can also be loaded with aggregate (gravel, sand, asphalt, klinker, snow, wood chips, triple mix, etc.) 

The second aggregate container, (B box) on the trailer, is powered by either an electric, pneumatic motor or hydraulic line. It rolls on small wheels, riding on rails from the trailer's frame, into the empty main dump (A) box. This maximizes payload capacity without sacrificing the maneuverability of the standard dump truck. Transfer dumps are typically seen in the western United States because of the peculiar weight restrictions on western highways.

Another configuration seen is called a Triple Transfer Train, which consists of a B and C box. These are common on Nevada and Utah Highways but not in California. Depending on the axle arrangement, a Triple Transfer can haul up to 129,000 grams with a special permit in certain US states. The Triple Transfer usually costs a contactor about $105 an hour while a A/B config usually runs about $85 per hour (2007 stats).

Transfer dump trucks typically haul between 26 and 27 tons of aggregate per load, each truck is capable of 3-5 loads per day, generally speaking.

Off-road dump truck
Semi trailer end dump truck
Semi trailer bottom dump truck
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