ABSTRACT
Hybrid electric–diesel engine technologies could reduce fuel consumption in buses by around 40%, with various studies identifying fuel consumption savings of between 10% and 75% depending on operating conditions. Most of the benefit comes from regenerative braking—storing 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, but hybrid engines also have wider benefits, such as reducing emissions and noise and providing smoother acceleration and braking. The costs associated with hybrid technologies are significant, though, with hybrid vehicles currently costing around 50% more than conventional buses. The lithium-ion batteries are the largest additional cost component, and there is considerable uncertainty over their longevity. This entry investigates the economics of introducing hybrid bus technologies from a through-life perspective. We find that fuel and emissions savings alone provide a relatively weak case for investing in hybrid buses based on current prices. However, as the cost of fuel rises, and when social and environmental impacts of motor vehicle use are better accounted for, hybrid technology outperforms conventional diesel technology.
