The long hood on a locomotive is actually the rear of the machine. The diesel engine is located under the long hood as are the radiators, generators and exhaust. Many doors line both sides of the long hood and provide access to the engine and other critical components of the locomotive. Typically, when used as a solo power unit on a train, the long hood will be facing rearward; however, the locomotive can be hooked to the train and operate with this long end pointed forward. Often when joined in teams, locomotives will be attached to each other with the long hoods together to provide easy shared access to both engines.
Locomotives are typically operated with the long hood facing the rear to allow better vision for the train crew. Another reason the locomotive is operated with the long hood to the rear is for crew comfort. The diesel engine and exhaust are under the longer hood, and heat from the engine as well as noise and smoke would infiltrate the locomotive's cab, making it unpleasant for the crew to operate the train for any length of time in that configuration. When a train is seen operating in this manner, it is often due to the inability to turn the locomotive around, and it is usually on a small working train.
Small yard or switching engines are sometimes operated with the long hood forward to assist the crew with hooking and unhooking many cars in a shift. By eliminating the need for a switching crew to have to walk the full length of the locomotive both to and from every car coupling, a great deal of time and energy can be saved. Placing the cab of the engine closer to the working end of the locomotive allows the crew member to climb on and off much closer to the work area. This also places the engineer closer to the crew member coupling and uncoupling the train cars to the power unit.
Occasionally, a locomotive is operated long hood forward due to a safety reason. If the locomotive's headlight should go out on the short hood side, it may be operated long side first to utilize the headlight on the long side. This saves valuable time in stopping the train to make repairs. The engines can be easily switched at any spur track so the train can continue on its way with an operational headlight. Once back at the yard, the headlight can be repaired on the short side and the locomotive can resume operation in the traditional position.