A tank truck, gas truck, fuel truck, or tanker truck or tanker, is a motor vehicle designed to carry liquids or gases on roads. The largest such vehicles are similar to railroad tank cars which are also designed to carry liquid loads. Many variants exist due to the wide variety of liquids that can be transported. Tank trucks tend to be large; they may be insulated or non-insulated; pressurized or non-pressurized, and designed for single or multiple loads (often by means of internal divisions in their tank). Some are semi-trailer trucks. They are difficult to drive and highly susceptible to rollover due to their high center of gravity, and potentially the free surface effect of liquids sloshing in a partially filled tank.
A tank truck is distinguished by its shape, usually a cylindrical tank upon the vehicle lying horizontally. Some less visible distinctions amongst tank trucks have to do with their intended use: compliance with human food regulations, refrigeration capability, acid resistance, pressurization capability, and more. The tanks themselves will almost always contain multiple compartments or baffles to prevent load movement from destabilizing the vehicle.