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Low Emission Transport - Buses

12th April 2019

In 2017, 44 (out of 51) British towns failed air quality tests. For every person living in those areas, this has been equated to smoking a cigarette a day, or 18 packs a year. (Source: World Health Organisation, May 2018; Berkeley Earth model). 

Public transport presents an opportunity to significantly improve air quality in city centres, because of the pollution it can create. Surprisingly, one local authority client established that 25% of the total air pollution in its city centre, was created by its own diesel bus fleet, with Park and Ride services being a significant contributor.

Buses pose an interesting challenge when assessing the viability of reducing emissions and there are several types of low emission buses, each type with its own merits for specific applications:


A hybrid bus can help reduce city centre emissions where it is acting as a long-range shuttle service between cities. The bus uses its battery for the city-centre-parts of its route, and then recharges the battery using the diesel engine while traveling on open roads. However, this does effectively just move the pollution away from the most affected area, rather than remove it completely. And of course the additional weight of the combined diesel and electric propulsion systems reduces the efficiency of whichever is being used at the time.


The key benefit of a Hydrogen bus (aside from zero emissions) is the time taken to refuel. So operationally, hydrogen buses can function in much the same way as a conventional diesel fleet. However, there is a reticence amongst planners to allow hydrogen storage in built-up areas, and the infrastructure is not yet well established. Public perception in terms of safety also has some way to go, despite the historic risks associated with petrol which have been largely mitigated. These factors contribute to a current lack of refueling infrastructure.

Fully Electric (overnight charging)

For shorter routes, fully electric buses can also offer immediate and dramatic air quality improvement, and with power more readily available than hydrogen storage, they present operators with a practical solution that can offer a lower long-term cost of ownership than a diesel fleet, today. The main drawback with this method applies in areas where routes are longer, or in more hilly regions – vehicles may need to be rotated during the day. This increases cost, as well as depot space requirements, which can already be at a premium.

Fully electric (overnight and opportunity charging)

As with the previous example, immediate benefits of a fully electric bus can be realised. The addition of a pantograph on top of the bus enables it to top-up the battery while stationary at bus stops using a compatible charger that hangs over the bus and connects with the pantograph. This can considerably extend the range, making length or topography of a route less of an issue, however there is an increased initial infrastructure cost, subject to requisite power being available at bus stop locations.

How we can help

Given the urgent need to kerb and then reduce air pollution, we’re pleased to be working with industry partners and local authorities to drive change in this area.

Our team of experts, some with up to 40 years’ experience in the Highways Technology field, work closely with clients to understand their aims and objectives. Each scenario is assessed on its own merits with the latest viable options to move forward presented to the client.

We can help you access several potential funding sources with the likelihood that we’ll be able to provide a feasibility study for your organisation with up to 100% cost subsidy.

To find out more about our low emission transport feasibility studies service, please contact our Transport Technology consultants, Ed Tallents or Simon Reeves.

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