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Could trolleybuses be the incredible solution for greener public transit?

Replacing the beloved transport vehicles with battery electric buses, experts argue, could be more polluting

People photograph the trolleybuses on their last day of peak hour service in Massachusetts.
People photograph the trolleybuses on their last day of peak hour service in Massachusetts. Photograph: Henry Pan
People photograph the trolleybuses on their last day of peak hour service in Massachusetts. Photograph: Henry Pan

One slushy March evening, about 100 people gathered at a bus lot in Cambridge, Massachusetts, directly to the north-west of Boston, to commemorate the end of a transportation era.

The guest of honor? Massachusetts Bay Transportation Authority’s trolleybuses – sometimes called trackless trolleys – which have poles connecting to overhead wires that draw electricity to run their motors. The buses, along with the 86-year-old network of wires that support it, were being decommissioned after serving the Boston area faithfully for the past two decades, in part because they were getting difficult to maintain. As the trolleybuses grumbled along for one last evening, participants onboard reminisced, running off at various intersections to take photos of their ride making turns it hadn’t made in years.

“When I heard that [the MBTA was] going to be discontinuing the trolley service … I was heartbroken,” lamented Northam von Posten, a former MBTA trolleybus driver who attended the commemoration. “I really came to love these buses, these electric trolleys.”

Colloquially referred to as “the T”, the MBTA plans to replace the trolleys with battery-powered electric buses over the next two years.

But some critics say even battery-powered electric buses are not as energy efficient as their trolley counterparts, arguing that US public transit systems trying to reach zero emissions should look to their past. Their skepticism comes at a time when other transit agencies in North America are pledging to stick with trolleybuses, and perhaps even expand their fleets to address the climate crisis. The case to keep trolleybuses around is simple: they run 100% on electric power, something even battery electric buses, which struggle to heat their inside efficiently in below-freezing temperatures and sometimes require the use of diesel fuel, cannot claim. It’s a tantalizing premise – if cities are willing to devote resources to their upkeep.

Trolleybuses existed as early as the 1880s when a German electrical engineer named Werner von Siemens attached a pole collecting current from overhead wire to a wagon. They became prominent during the Great Depression, when many cities running trams wanted to keep their wires but not the costs of maintenance and labor; trams in most cities required two people to run, whereas trolleybuses needed only one.

In Boston, the MBTA ran trolleybuses until March of this year. The public transit agency says it had a few reasons for shuttering the trolleybus system: first, it would be expensive to maintain and renew – something local transit advocacy organization TransitMatters disputes. Second, if the overhead wires were damaged or had ice on them, then the buses could not run because they had no backup power source. Finally, construction happening on the roads where the trolleybuses ran would require the agency to dismantle the supporting infrastructure, such as the overhead wires, anyway.

“We frequently – and by frequently, I mean more than 15% of the time – have to pull these trolleybuses and replace them with diesel bus service whenever there’s any unplanned issues with the overhead catenary system [such as] trees falling, ice, [or] emergency or planned road work,” said Scott Hamwey, MBTA’s director of fleet modernization at a February meeting discussing their future.

The MBTA plans to replace them with battery electric buses, joining agencies across the US, which the agency believes will help them maintain electric-powered service where the trolleys once ran.

But battery-electric buses have their own drawbacks. They do not perform well in places where lingering temperatures fall below freezing; when temperatures hit -6C (21.2F), the distance that MBTA’s existing battery electric buses can travel drops by almost half.

To ensure they can run and keep passengers warm, the MBTA learned it needed to install diesel-powered heaters, meaning the battery electric buses will be more polluting than the zero-emissions trolleybuses they replace.

San Francisco Muni’s electric trolleybuses parked at a depot.
San Francisco Muni’s electric trolleybuses parked at a depot. Photograph: John G Mabanglo/EPA

It’s why Omriqui Thomas, who will start high school in the fall and lives along the trolley routes in Cambridge, was disappointed when she heard of the T’s plans. She wants to see the MBTA further invest in trolleys, by buying new trolleybuses that can operate on batteries, which would allow the buses to go off-track and run without being connected to an overhead wire.

“If they use battery assisted trolleybuses, they wouldn’t have [to have battery electric buses that use diesel heaters] and it would still be fully electric. The T’s decision doesn’t make a lot of sense, and it’s sabotaging the future generations,” said Thomas as she rode a trolleybus with friends a day before they ceased to run.

This technology – where trolleys come equipped with batteries that charge while they’re moving or parked – has been adopted by transit agencies in San Francisco, Seattle, Dayton, and Mexico City in the past decade. TransLink, which serves the metropolitan area of Vancouver, may also join them later this decade.

Battery electric trolleybuses aren’t perfect for all types of terrain and weather. King county, which encompasses Seattle, hesitates to use them on weekends, when the overhead wire system is turned off so construction workers can work safely. The local transit agency worries about the hills and below-freezing temperatures that the area is known for, which significantly reduce the battery’s range.

“So to have a trolley on [battery] and go out and try and do that body of work doesn’t make operational sense. It doesn’t benefit the longevity of the [battery], said King county metro fleet procurement superintendent Bill Thon.

It is possible to equip trolleys with higher capacity batteries, something Kiepe Electric, which provides the traction for San Francisco, Dayton, and Seattle’s trolleybuses, is working on with the San Francisco Municipal Transportation Agency (Muni).

“New technology allows [us] to … significantly increase the off-wire range and thus the possibility to ‘electrify’ additional routes,” says Klaus Peter Canavan, Kiepe Electric’s CEO, who says the upgrade may make it possible for the city’s trolleybuses to run anywhere in the city. In fact, Muni is already running portions of two routes off-wire for a three-mile round-trip.

Environmentalism and the 1970s oil crisis influenced the Greater Dayton RTA to maintain and expand its 125-mile trolley network. Most recently, the agency renewed its trolley fleet with 45 new trolleybuses, 43 of which have batteries allowing them to operate off-wire for 10 miles.

“Trolleys are here to stay in Dayton. We have the infrastructure in place, and it means we already operate electric buses when others are just now trying to catch up on electric technology,” said Bob Ruzinsky, RTA’s CEO. “With our electric trolleybuses, we are ahead of most agencies on being green.”

Still, if cities want to build new or expand their trolleybus systems, acquiring more buses may be a challenge. Manufacturers are few and far between, and only Winnipeg-based New Flyer and Kiepe Electric are able to build trolleybuses that meet a US law that requires most manufacturing costs be spent domestically.

Muni hopes to work with agencies like King county and Translink, which plan to renew their trolley fleets in the coming decade, to court more manufacturers to build trolleybuses. “They are the perfect vehicle for San Francisco, particularly given our hills. I want to do everything that we can to continue keeping and promoting them,” said Muni head Jeffrey Tumlin.

But with a state zero-emissions fleet transition requirement looming, Muni is looking at all of its options. Since February, the agency has been testing battery electric buses on its busiest routes, which include existing trolleybus routes.

“We’re committed to completely decarbonizing mobility in San Francisco. And we know in order to do that, we’re going to need to take many approaches all at the same time, including figuring out the optimal role for battery electric buses,” said Tumlin.