A heavy-duty truck uses either a push- or pull-type clutch. Trucks equipped with high-torque engines and designed to haul heavy payloads use a two-plate clutch. Two-plate clutches double the friction contact area of the clutch compared with a single-plate clutch. The additional friction contact surface area is necessary to transmit the high torque to the transmission without slippage. Lighter-duty trucks may use a single-plate clutch assembly. Clutches used with automated transmissions are managed electronically but use the same fundamental as mechanical clutches.