They’re zero-emissions. They drive themselves. And they’re longer than a blue whale. Can the humble city bus get a modern makeover?

Local Motors introduced its first driverless bus, Olli, in Fort Washington, Maryland. (Local Motors)

When French mathematician Blaise Pascal* introduced the world’s first public bus service to Paris in 1662, it was little more than a fleet of seven horse-drawn carriages that ran along three regular routes, carrying six to eight passengers each. (Perhaps too novel for its times, the idea didn’t really catch on until the 1800s.)

Buses have come a long way since Pascal’s horses and buggies. They represent almost half of public transit trips in the U.S., and are increasingly trumpeted as key to multi-modal transport and to urban sustainability. “If you take seriously the climate change challenge and the need to provide more alternatives to the automobile, there are many corridors where the only realistic option is bus,” says Fred Salvucci of MIT’s Transit Lab. Bus lines are cheaper to establish and more flexible than rail-based transit. But the ponderous, diesel-spewing machines don’t tend to get the same love as subways, trains, and streetcars.

That could be changing soon: Rolling onto the scene are fleets of high-tech vehicles with self-driving capabilities, zero-emissions engines, and all sorts of innovations that promise to make them not only greener and more efficient but also, transit advocates hope, more attractive to riders. “I think we're going to see bus grow more than most people think,” says Salvucci.

Here’s a roundup of some of the new technologies that might give the humble bus a modern makeover.

Wave goodbye to the bus driver

Demonstration of a self-driving bus in Tokyo. (Toru Hanai/Reuters)

While many speculate that the autonomous vehicle technology now being pioneered by the likes of Tesla, Google, Uber, and (maybe!) Apple could spell the end of public transit, others are convinced of the opposite: AVs may roll out first not in private vehicles but in shared, public ones—driverless buses with sensors and artificial intelligence behind the wheel. In fact, some are already being tested in a handful of cities, from Helsinki, Finland, to Washington, D.C., to the city-state Singapore.

Among the vehicles vying to lead the autonomous bus race is Olli, a self-driving electric minibus from the Arizona-based Local Motors. It’s the first of its kind to use IBM’s cognitive Watson technology to interact with passengers. The bus can be summoned in Uber-like fashion, can answer questions about routes and nearby attractions, and could eventually personalize the trip by linking with the passengers’ social media accounts. Here’s an IBM video on Olli’s test run in Washington, D.C. this past summer.

Other autonomous shuttles are also making appearances in cities worldwide. Currently, these experimental fleets aren’t as advanced as driverless cars: They poke along at anywhere between six and 15 miles per hour depending on the maker and each city’s safety restrictions, and the ones already in use provide limited service in controlled setting. Driverless buses in Helsinki, for example, are focused on providing “last-mile” service and carry about a dozen passengers per vehicle. They debuted in September, running at seven miles an hour on a straight, quarter-mile route. Even at that kind of speed, some buses get into trouble when sensors encounter an atypical situation. One program in Switzerland had to be suspended after it bumped into the open tailgate of a parked van.

These shuttles might help address the concern that single-passenger AVs will trigger overwhelming urban congestion. But Salvucci sounds a cautionary note. "Streets are very complicated environments to drive in; you got jaywalkers and bike riders who sometimes dart out in front of the bus,” he says. “I think solving the technology problems for an urban bus to be safe is going to be very tough.” Even assuming that buses are equipped with proper safety features, there’s the potential problem of pedestrians adjusting their behavior for the worse. That’s the basis for one recent research paper that uses game theory to suggest that when pedestrian learn that autonomous vehicles always stop for people, they’ll jaywalk with impunity.

Robo-buses, therefore, are “not high on my list on what would make public transportation more viable,” Salvucci says. So what is?

How about the world’s longest bendy bus?

Don’t cut in front of this thing: The longest articulated bus in the world has three sections and can carry 300 people. (Volvo Group)

Bus rapid transit systems, which give exclusive lanes to high-capacity, limited-stop buses and can move lots of people around quickly, got a boost last week when Volvo introduced the world’s longest “bendy” bus, which will be put to use next year in Rio de Janeiro, Brazil. The Gran Artic 300, as it’s called, is a 98-feet-long double-articulated bus with three carriers connected by two accordion-like joints. It can carry up to 300 people, about 30 more than the capacity of today’s largest buses, according to the Volvo Group. And it was made specifically for the planned Transbrasil line, a BRT system that will run 14 miles across the city, with 16 stations and 17 walkways serving some 820,000 passengers each day. The notion of sharing the road with a vehicle as long as a pair of mosasaurs may be daunting (when it merges, it’s like letting eight cars cut in front of you), but since they will run in dedicated lanes, other motorists won’t have to interact with these beasts. Plus, the added capacity should cut down the number of buses overall, thereby cutting costs per passengers for operators and reducing emissions.

BRTs are a a relatively low-cost alternative to fixed-rail systems in cash-strapped cities in Brazil and Colombia. And they work. One of the world’s first BRT system, in the city of Curitiba, is highly regarded. The big buses don’t get stuck in traffic, and having passengers pay before they get on the bus helps that the system run smoothly. Extending BRT systems is one of the top priorities listed in the C40’s recent action plan for cities limiting global temperature increases over the next four years.

But the success of BRTs in Latin America comes with a note of caution, according to Salvucci. “They are useful tools in a complicated transportation strategy in major metropolitan areas, but generally speaking you probably want to convert them to rail once they succeed in attracting a lot of people,” he says. Why? Capacity. Even with Volvo’s latest creation, the capacity per bus is still hundreds fewer than what a set of railcars can shuttle in one trip. “I think the enthusiasm for them may be a little overdone,” he says.

Zero-emission upgrades

Proterra launches its latest electric bus this week, the Catalyst E2 Series (Proterra)

They may be a rare sight in U.S. cities, but globally, there’s a growing market for fully electric buses. China, for example, is expected to have doubled its purchases of electric buses, from 10,000 in 2015 to 20,000 by the end of this year. That growth will likely continue as the country tries to tackle its lung-searing air-pollution problem. In the U.S.—the second largest carbon polluter behind China—numbers are far lower: The Department of Transportation estimates that roughly 300 of the country’s 71,000 transit buses are zero-emission. But the federal government is pushing to raise those numbers with $55 million in Department of Transportation grants to help transit agencies buy cleaner buses.

Proterra, a manufacturer of zero-emission electric buses, aims to get in on that action with their latest model, the Catalyst E2 Series. The company says the battery-powered bus can drive up to 350 miles on one charge, enough to cover a day’s worth of routes (and comparable to a new Tesla, which can drive up to 400 miles before needing a shot of juice).

Cost will be one big hurdle: A battery-powered bus from Proterra comes with a hefty price tag of $800,000, more than double the cost of that cities pays for a diesel bus. But the company says the new models will save owners up to $237,000 in the long run, as it should require fewer repairs (and no oil changes). Salvucci seems to think that the electro-bus might have legs. “If battery-operated bus [become] financially viable, I think they could be come an interesting part of the urban picture in a lot of cities,” he says.

London’s mayor, Sadiq Khan, is encouraging another kind of zero-emission buses: ones that run on hydrogen fuel. Last month the city unveiled the world’s first hydrogen-powered double-decker and announced plan to at least 20 new buses next year as part of Khan’s goal to phase out diesel buses entirely by 2020. He wants to have 300 zero-emission buses on London street by then.

While we’re at it, the bus stop could use an upgrade too

Fighting pollution doesn’t stop with the buses themselves: Commuters are exposed to a elevated rates of pollution at bus stops. In Singapore, for example, a study suggests that bus commuters may be breathing in more than three times the level of toxic gases while waiting for their rides. And in London, which suffers from some of the world’s worst nitrogen oxide pollution, the mayor issued an alert earlier this month about its thick smog, placing notices throughout its 2,500 bus stops and 270 subway stations. One possible fix? Airlabs, a London-based startup, is fighting the smog monster at the pedestrian level by installing filters that reduce the level of nitrogen oxide from exhaust fumes at London bus stops and subway stations.

So, as they wait for their zero-emission buses of the future, at least commuters can breathe a bit easier.

CORRECTION: An earlier version of this post reversed the names of the legendary French mathematician and mass transit innovator.  

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