Developing electric bus driving cycles with significant road gradient changes::A case study in Hong Kong

Abstract

Battery electric buses have been increasingly being deployed to replace traditional diesel buses in providing urban public transport services. Accounted for over 30% of daily passenger trips, the franchised bus system in Hong Kong only retained a few battery electric buses after its trial programme. Under the unique bus driving environment in Hong Kong, more evaluations are anticipated for further deployment of electric buses. Driving cycle is a widely adopted platform for the assessment of vehicle fuel economy, energy consumption, emissions and driving range. Therefore, it is necessary to have a purposely developed driving cycle for battery electric buses. A comprehensive review of bus driving cycles developed elsewhere shows that the impacts of road gradients are seldom considered. Therefore, in this study, the only remaining battery electric bus route with significant gradient changes was selected for speed data collection and synthesis for a set of driving cycles. Results shown that driving characteristics of this route were comparable to urban bus cycles developed in other cities, but were slightly different from bus cycles developed for other conditions. It was also observed that battery electric buses appeared to be less responsive to drivers’ acceleration activities than that of a supercapacitor bus.