2-6-6 Definition

Under the Whyte notation system, a Mallet-type locomotive with two leading wheels on a leading truck, two sets of six driving wheels, and no trailing wheels.

Under the Whyte notation system, a Mallet-type locomotive with two leading wheels on a leading truck, two sets of six driving wheels, and two trailing wheels on a trailing truck.

Under the Whyte notation system, a Mallet-type locomotive with two leading wheels on a leading truck, two sets of six driving wheels, and four trailing wheels on a trailing truck.

Under the Whyte notation system, an articulated locomotive with two leading wheels on a leading truck, two sets of six driving wheels, and six trailing wheels on a trailing truck. This arrangement was used only on the C&O which called it the Allegheny and the Virginian, which named it the Blue Ridge.