Lean, Green and Rescuing on Scene Making an efficient lightweight, aerodynamic ambulance

Since the gauntlet was laid down to the NHS to cut carbon emissions by 10% by 2015, Yorkshire Ambulance Service NHS Trust (YAS) has been working hard to reduce its carbon footprint through innovative technologies, the most recent of which has been the introduction of lightweight, aerodynamic ambulances to its fleet.

The Trust developed a Carbon Management Plan which identified ways to reduce its carbon footprint. With two-thirds of its Scope 1 carbon footprint being from transport, work began to look at ways of decreasing carbon emissions and fuel consumption across its fleet.

The UK’s Engineering and Physical Sciences Research Council (EPSRC) funded a Knowledge Transfer Secondment partnership project between YAS and the Schools of Civil Engineering and Mechanical Engineering at the University of Leeds and they worked with four Yorkshire-based vehicle manufacturers. This enabled YAS to identify opportunities for major carbon reductions through the creation of a more efficient aerodynamic ambulance.

The research project included a Computational Fluid Dynamics (CFD) analysis, which looked at the aerodynamics of the box body ambulance and the aerodynamic drag forces for several different ambulance designs. The initial work showed that the aerodynamic drag forces on the common box body ambulance designs could be reduced by up to 20% by using aerodynamic styles common in other vehicle types, eg Heavy Goods Vehicles.

It showed that the addition of light-bars on ambulance roofs leads to a 20% increase in the aerodynamic drag. Using a roof design concept, based on aerofoil shapes common in the aerospace industry, the University of Leeds was able to significantly reduce the impact of the light-bars so that they would only increase the aerodynamic drag by 3% compared to ambulances without light-bars.

The work also highlighted the potential to reduce aerodynamic drag by up to 29% by buying van conversions rather than box body ambulances.

The four-year project culminated in the development of a bespoke lightweight van conversion with an aerodynamic light bar, built by Manchester-based ambulance manufacturer Cartwright, working from an aerodynamic design by the University of Manchester with an initial design from University of Leeds.

The new design was based on a Mercedes Sprinter 4.6 tonne super single van option and has incorporated a change from the rear axle from a twin-wheel rear axle to a single wheel, allowing for more space inside the ambulance.

The curb weight of the new vehicles is 3.75 tonnes in comparison to the previous ambulance design at 4.3 tonnes. The new vehicle has an increased carrying capacity of 800kg through innovative storage, lighter materials and equipment.

The new ambulance, built to strict European safety standards, has exceeded expectations by achieving fuel efficiencies of 26mpg (compared to 16-18mpg with box body ambulances).

Richard Smith, YAS Fleet Engineering Manager, said: “We have been working hard to look at a solution to our rising fuel bills and carbon emissions. This vehicle re-design shows that with collaboration between academia, public and private industries, it is possible to dramatically reduce our emissions and costs. We are really pleased with the results and will continue to make improvements to reduce our carbon emissions.”