In truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

 braking systems, one type of warning for low air pressure in an air brake system of commercial trucks is called the wig wag. This device drops a mechanical arm into view when the pressure in the system drops below 60 p.s.i. An automatic wig wag will rise out of view when the pressure in the system goes above 60 p.s.i. The manual reset type must be placed in the "out of view" position manually. It will not stay in place until the pressure in the system is above 60 p.s.i. The photo to the right shows a manual wig wag which the operator swings to the right out of view when the air pressure is above 60 p.s.i. where it will remain as long as the pressure is sufficient.

Most state CDL (commercial drivers license) manuals describe this term.

Sources

• California Dept. of Motor Vehicle CDL Manual section on air brakes