Evaluation of a fuel-efficient urban delivery vehicle

A novel fuel-efficient articulated urban delivery vehicle is developed and tested. The vehicle has a path-following steering system on the semitrailer which improves its manoeuvrability in narrow city streets. This enables the payload to be increased from 39.4 m3 of freight on a conventional rigid delivery vehicle to 84.2 m3 on this articulated counterpart, leading directly to up to 33% fuel saving per unit of freight task. The vehicle is also equipped with a hydraulic regenerative braking system which stores energy in hydraulic accumulators during braking events and releases this energy back to accelerate the vehicle in subsequent motion. The design of this system and the field testing programme are described. The experimental tests are used to determine the hydraulic losses and to validate a mathematical model of the vehicle and the regenerative braking system. Finally, the validated mathematical model is used to perform a parametric study for the vehicle operating in various standard driving cycles. It is found that operating the regenerative braking system with an engine stop–start system and optimized accumulator precharge pressures can reduce the fuel consumption by 9–18% in comparison with that of the baseline vehicle, depending on the driving cycle. When combined with the performance improvements due to the trailer steering system and additional payload, this gives an overall reduction in the fuel consumption of 35–42%.