Buses play a key role in the urban transport mix – and are also a major contributor to air pollution within cities. How can we have one without the other?

In the year to June 2020, more than two billion passenger journeys were made by bus in London – representing 14 percent of all travel. Sound a lot? In Rio de Janeiro over a similar period, the city’s bus rapid transit system recorded just over one trillion passengers, equating to 37 per cent of all journeys – one of the largest modal shares in the world.

A bus typically emits fewer greenhouse gases per passenger kilometre than a single occupancy car – 82g of CO2e per km compared to 180g for an average petrol car. However, since journeys are typically far longer than cars, the exposure to air pollution is higher. The number of buses on the road in many cities remains a significant contributor to air pollution: more than 16,000 operate daily in Kolkata, for example, helping to explain why it is the second most polluted city in India. Furthermore, according to the International Association of Public Transport’s 2019 Global Bus Survey, covering 320 operators in 46 countries, diesel still accounts for 50 per cent of propulsion systems used across the world.

A move from fossil fuel vehicles to zero-emission vehicles (ZEVs) will help address these issues. This is at the heart of the Clean Bus Declaration and Fossil Fuel Free Streets Declaration made by the C40 network.

In the UK, the Government’s Ten Point Plan for a Green Industrial Revolution, announced in November 2020, includes a National Bus Strategy. “Electrification is key,” says Dr Mike Bell, Ricardo’s Group Strategy and Transformation Director. “The strategy mentions funding for two all-electric bus towns and development of the first fully zero-emission city centre. A reference to £120 million for at least 4,000 ‘British-built zero-emission buses’ perhaps leaves the door open for hydrogen-fuelled buses too.”

Navigating the route to zero
Ricardo is already working with customers across all global transport sectors to reach a sustainable zero carbon future, building on its expertise in the development of clean, efficient, integrated propulsion and energy systems for advanced battery electric and hybrid vehicles. The company’s recent initial £2.5 million investment in a hydrogen test facility at its Shoreham Technical Centre is a clear statement of its vision to be a leader in hydrogen, defossilised fuels and electrified transport engineering.

The benefits of electrifying city buses are clear. They have predictable energy requirements based on repeat schedules which facilitate battery charging at depots. The Confederation of Passenger Transport, which represents 95 per cent of English bus operators, stated in 2019 that it plans to buy only zero-emission vehicles for use in cities. However, the route to an entirely zero emissions bus future is more complex, given the typical 10 to 15-year lifespan of a vehicle and the existence already of regulated low and zero emissions zones through which to navigate.

Battery electric and hydrogen fuel cell solutions both have a part to play in the decarbonisation of buses. The optimum solution for a given operator will depend on factors such as the operational requirements and local energy infrastructure. Hydrogen could provide an increased range and greater flexibility on operating routes and schedules, compared to a battery electric bus that requires more frequent or longer charging periods.

“The major bus original equipment manufacturers (OEMs) are offering both battery electric and hydrogen fuel cell products, so the technical solutions for decarbonisation are known,” says Will Missions, Chief Engineer at Ricardo. “The challenge is implementation. Buses have long service lives and so transitioning fleets to zero-emission vehicles will take many years, potentially decades, to complete.

“A key opportunity to accelerate decarbonisation is to make use of the existing assets and to retrofit the current vehicles with zero-emission powertrains. Another potential solution being explored by many truck OEMs is hydrogen-fuelled combustion engines. This approach has advantages for fast adoption through minimising change to the vehicle powertrain and manufacturing infrastructure.”

Geofencing [can] encourage more intelligent use of plug-in hybrid EVs to make sure they have the lowest possible impact on air quality

Optimising for flexibility
Geofencing - creating a virtual perimeter for a real-world geographic area - is at the heart of a Ricardo project underway in West Sussex.

As reported in the Spring 2021 edition of RQ, Ricardo has received funding from the Geospatial Commission in partnership with Innovate UK to enhance the use of transport location data so that hybrid electric vehicles can intelligently modify how they operate.

“The project is about using geofencing to encourage more intelligent use of plug-in hybrid EVs, which have limited zero-emission range, to make sure they have the lowest possible impact on air quality” explains Josh Dalby, Ricardo’s Chief Engineer for Technology Strategy.

“This application of geofencing involves adding smart on-board technology to a hybrid EV, allowing it to ‘sense’ when it is in an ultra low emissions zone and automatically switch its operating mode.”

Brighton & Hove Buses operates the UK’s first zero-emission geofenced fleet of 54 buses which are fitted with this technology to enable them to sense when they are in pre-defined areas and automatically switch to zero-emission mode. “Our focus,” Dalby adds, “is on optimising this fleet to enable it to use more flexible zones, rather than the current, static, pre-defined ones.

“During the first phase of the project, we are evaluating the benefits and feasibility of flexible geofencing both to existing buses and private vehicles. In the second phase, we plan to demonstrate this approach through some small fleet trials, while also developing the back-end system which would automatically define the optimum geofenced area for the different vehicles being driven in a city.”

Beyond that? “We’re looking to roll out and extend this technology to any city in the UK and, longer term, to any city internationally to reduce the emissions of existing fleets while fully zero-emission solutions mature and enter the marketplace.”

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