These engines engage and disengage as more or less horsepower is required

The Trainz SKU for this item is P11573176

The Trainz SKU for this item is P12343884

and the Southern Pacific® employed large numbers of them

Road Name: Isaly's

Accurail 9219 HO Burlington 89' Bi-Level Open Auto Rack Kit ProductID_12109168 These engines engage and disengageThis is an Accurail 9219 89' Bi Level Open Auto Rack Kit, Burlington Route Trailer Trains # 800157 Kit. The easy to build kit includes a detailed body and working knuckle couplers. Condition: Factory New (C 9) Operational Status: Functional Original Box: Yes (P 9) Manufacturer: Accurail Model Number: 9219 Road Name: Chicago Burlington & Quincy (CBQ) MSRP: $22. 98 Scale Era: HO Scale Model Type: Freight Cars The Trainz SKU for this item is P11998241.