Take the (electric) bus: public transport and air pollution

Getting on the bus rather than taking your car has long been a tenet of green city living — an orthodoxy that is somewhat challenged when you look at the greatest sources of NOx and particulates in many major cities. Although there are far fewer buses than cars, their large diesel engines, combined with stop-start journeys and idling at stops, means that a city’s bus fleet can produce more pollution than all its petrol cars combined. Of even greater concern might be the fact that a disproportionate amount of bus emissions occur when the bus is leaving a stop — so those waiting for the next bus can experience up to 150 times the pollution levels of pedestrians just a block away.

Cleaner diesels, hybrids and gas-powered buses are improving the situation for those cities able to adopt them. Cleanest of all, with virtually zero emissions, are electric buses. Replacing the oldest, dirtiest buses with electric models can be one of the quickest and most effective ways to reduce both NOx and particulates in city streets.

“So far the main barrier preventing cities from doing this is the upfront cost,” says Nick Albanese, an expert in electric transport with BloombergNEF. “At between US$570-870,000, they are around $250,000 more expensive than diesel equivalents. For this reason their adoption has been limited to places like China, California and Europe where government subsidies have made up the difference.”

They also require charging infrastructure. Newer electric buses have 350kWh batteries with a range of more than 200 miles, enough for a whole day of journeys, before they are charged overnight in the depot. “These are the pricier buses,” says Albanese. “Cheaper, lower range models can still be useful for shorter routes.”

Another way of dealing with range issues is to install wireless induction charging technology — for example, at bus stops — so buses can pick up a charge along with passengers. Chattanooga in Tennessee is one of a limited number of cities adopting this technology. “In general this kind of infrastructure is expensive and charging tends to be slower,” says Albanese.

Such innovations could soon be superseded by rapid improvements in batteries. “Battery costs have reduced by over 85% since 2010. The technology is also better. Some municipalities were concerned about batteries not performing well in cold weather, for example, but many of these concerns have now been addressed by manufacturers.”

Currently some 99% of the world’s electric buses are operating in China, where they comprise 18% of all buses, according to BloombergNEF’s 2019 Long-Term Electric Vehicle Outlook. In comparison, electric buses represent just over 1% of all municipal buses in Europe. The UK now leads the way with 381 buses, narrowly overtaking the Netherlands, which has 371.

The picture is changing swiftly, however, and by 2030 Albanese believes things will look very different. “Technological and manufacturing improvements mean that price parity with diesels should occur around 2030 or perhaps even earlier. That will be a game-changer.” Major regulatory moves will also put far more e-buses on our roads: California has said that all new buses procured by cities must be zero emission by 2029, and the EU wants 33% of buses to be “clean” by 2030. Many cities, including London and Amsterdam, are imposing stricter targets.

Ironically, says Albanese, it is the rapid improvement in technology that is delaying adoption of electric fleets in some areas. “Cities are calculating that electric buses will soon be cheaper and better, so they think they will wait until they are better value.”

For those queuing for the bus, however, the wait will not be a pleasant one.

This article appeared in The Possible issue 05, as part of a longer feature on improving air quality in cities