<div class="htmlview paragraph">A theoretical and experimental investigation into the use of elastomers as the energy storage element of a regenerative braking system for urban vehicles is being carried out. This work has included the design and fabrication of full-scale elastomeric energy storage units which were tested to investigate energy density, efficiency and stress-relaxation. A complete small-scale system which simulates a vehicle was tested during transient speed conditions, and a complete full-scale system to be laboratory tested is under construction.</div>