The concept of a hybrid braking energy recoupment system was defined for coaches of diesel-hauled regional commuter trains. Functional specifications were developed having the goal of increasing by 25 percent the acceleration rate of a commuter train consisting of 10 bi-level coaches hauled by a 3,000 hp diesel locomotive, typical of the rolling stock now in service in Canada and the U.S.A. Because increasing train acceleration was the primary aim, the concept was named the Hybrid Augmented Traction System (HATS). Analyses of HATS simulations showed that in addition to augmenting acceleration and reducing trip time, braking energy recoupment reduced fuel consumption and corresponding diesel emissions.
Examined were three alternate hybrid systems for train retardation by recoupment of braking energy, its storage and then regeneration based, respectively, on Hydrostatic, Battery and Ultracapacitor energy storage. The Ultracapacitor Hybrid system appeared the most promising due to the capability of ultracapacitors to repeatedly and rapidly accept large charges, be temperature insensitive and flexible in the placement of modules in the limited space available. The study foresees that HATS technology development could be expedited via the procurement process if railway operators specified braking energy recoupment requirements in calls-for-proposals for new capital equipment.