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Analysis suggests autonomous transit would be most efficient use of AV technology

April 27, 2017

Authors make the case for employing AVs in ways to minimize VMT increases

Mobility Lab has often stressed the importance of autonomous vehicles being introduced as fleets rather than personally owned, so what might those fleets look like? How would this emerging technology be applied to the transit solutions already known to work?

If autonomous rapid transit – also referred to some places as “ART” – became widely used, it could reduce vehicle-miles traveled and limit the associated impacts of private AVs. Imagine small buses and shuttles as a new form of transit, moving along in dedicated lanes or car-free city centers.

As Peter Calthorpe and Jerry Walters write in their article on the Urban Land Institute’s Urbanland blog, “Autonomous Vehicles: Hype and Potential,” autonomous rapid transit could be just that: a low-cost, 24/7 service, that avoids meandering miles and miles without passengers (as AV taxis might operate, on their way to pick up passengers).

Further, autonomous transit could be like bus rapid transit, but without the cost of paying for a driver. It could also, according to Calthorpe and Walters, run more efficiently by “tailoring capacity by time and place to match demand,” could cut travel time, and could function more like an on-demand service during off-peak hours. On-demand service during off-peak hours would reduce inefficient low-occupancy service, eliminate late-night shut-downs, and allow the service to operate 24/7 without ever running zero occupancy vehicles.

Calthorpe and Walters cite an unpublished study by their consulting groups Fehr & Peers and Calthorpe Associates that explores the option of replacing proposed BRT along Geary Boulevard in San Francisco with ART. In two dedicated lanes, the authors imagined replacing buses with platooning fleets of four-person AVs, which would gather three or four passengers and take them to their destinations, skipping unnecessary bus stops along the way.

In the end, Calthorpe and Walters suggest ART reduced travel times by 35 percent compared to the BRT proposal, and by 50 percent compared to private vehicles in their corresponding lanes. Rush-hour ART could also carry as many as 3,000 to 4,000 people each hour, the same as current international BRT systems. That’s more than five times the capacity of an urban car lane, they write.

ART could also attract riders more accustomed to driving themselves rather than taking transit, given its relative privacy, direct-to-destination service, and shorter travel times.

Addressing autonomous tech’s benefits and consequences

While ART sounds like a great transit option, there’s much we still don’t know about the technology behind it. Applying autonomous possibilities in a transit context, even early on, could be important because widespread use in personal vehicles carries the high possibility of traffic and sprawl-inducing effects.

Personal autonomous vehicles are generally known for their potential to operate well with other AVs, syncing to move as a so-called “platoon” and working together at intersections. But throw in bikes, pedestrians, person-driven cars, motorcycles, and everything else, and what do you have? Inefficient traffic flow and more congestion, say Calthorpe and Walters. More research is confirming that personal AVs could worsen traffic nightmares.

Induced trips could be added in the form of, for example, trips taken because the stress of driving is no longer a factor, empty cars running errands for people, and having “zero-occupancy vehicles” picking up people. Calthorpe and Walters say this increase in VMT could cause sprawl.

In a taxi model, AV cars then could also roam in between passengers, ratcheting up VMT per passenger. So high, that in the next 30 years, it would exceed the past 30 years’ rate of VMT growth by five times.

But if AVs are shared and used as mass transit connections, they might actually lower VMT. This is where the efficient transit function that Calthorpe and Walters put forth pays off.

“There are a lot of positives to an AV transit-like fleet,” said Paul Mackie, Mobility Lab’s communications director. “For one, they could make access to society a lot easier for people who can’t drive, like some seniors and those with disabilities.

“If we can take some of the people who currently drive alone and make it easy for them to instead take autonomous rapid transit straight to work or at least to a bus or train, then those who are driving will be a lot less miserable in traffic. Given the high cost of personal AVs, governments will have the time to figure out how this transportation system of the future is going to work.”

Photo: A bus passes a pedestrian on Geary Boulevard in San Francisco, the focus of Calthorpe and Walter’s analysis. (Gabriel White, Flickr, Creative Commons).

 
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