Hybrid electric-diesel engine technologies offer the potential to reduce fuel consumption in buses by around 40%. These savings
can largely be attributed to regenerative braking – the ability to store in a battery energy that would otherwise have been lost
under braking. Lower fuel consumption makes sense economically for bus operators through reduced running costs; hybrid
engines have other wider benefits, though, such as reducing emissions and noise, and providing smoother acceleration and
braking. The costs associated with hybrid technologies are significant, however, with hybrid vehicles currently costing around
50% more to buy than conventional buses.
With Alexander Dennis and BAE Systems, UCL is conducting a three-year systems engineering research and development
project to adapt and optimise hybrid buses for the UK and European market. This paper investigates one aspect of this project –
the costs and benefits of introducing hybrid bus technologies from a whole-life perspective. We find that fuel and emissions
savings alone do not provide a compelling case for hybrid buses based on current prices. However, as the cost of fuel rises, and
when the social and environmental impacts of motor vehicle use are better accounted for, hybrid technology outperforms
conventional diesel technology
