Another form of Consisting
Distributed Power is another form of Multiple Unit Consisting, which has origins in the 1960s.
Instead of all the motive power being located on the front of the train, locomotives will be located in the middle of the train as well. They are controlled from the head end via radio control. Older consists used a robot to control the mid train locomotives. Robots were usually converted B unit locomotives, whose prime mover had been replaced by radio equipment.
These locomotives keep the coupler slack to a minimum and assist in braking. The position in a long train allows the brakes to operate faster. Pressure changes in the brake pipe take time to propagate through the length of the train, and longer trains mean longer time for the complete application to take place.
This technique also reduces the amount of stress on the drawbar as the entire train is not being pulled from the head end. DP allows for longer trains by reducing the load on the drawbar of the front end locomotives.