Charlotte Leis

December 8, 2017

Self-Driving Sprawl?

A recent New York Times article looks at the daily life of an extreme commuter outside San Francisco. Ms. Sheila James makes a two and a half hour commute from Stockton to San Francisco each day – she relies on her car, two trains, and a bus to travel the 80 miles from home to work. Other commuters eschew public transit and drive this route instead. Alert at the wheel before the sun has risen, their commute is in some ways just as hard as Ms. James’s, even if it might not be quite as long.

The introduction of AVs could significantly improve the lives of super-commuters like Ms. James. Instead of leaving the house before 4am to take transit to work, she could schedule an AV chauffeur to pick her up and drive the 80 miles while she slept – or at least relaxed, because even if the vehicle was L3 rather than L4 she wouldn’t have to actively drive the entire way. If other commuters near her Stockton home were also heading to San Francisco (as they likely were), Ms. James and her neighbors could commute together in a large (L4) AV and sleep, read, or otherwise relax.

There is, however, a downside to making super-commutes like Ms. James’s easier.

Exurbs, the suburbs of suburbs, are growing.

If AVs make lengthy commutes easier, workers may choose to live further and further from their jobs. Right now people are limited in how far from work they can live based on their willingness and ability to commute long distances. If AVs make long commutes less of a nuisance, it is possible that people will continue to move further away from cities into increasingly large and sprawling exurbs. (Exurbs are most easily described as the suburbs of suburbs, and they’re growing quickly.)

Houston Post-Harvey, showing the risk of sprawl building on wetlands.

As cities become more and more sprawling, they often run into land that cannot be wisely and safety built on. The disastrous results of unregulated sprawl was seen most recently when Hurricane Harvey hit Houston, destroying entire neighborhoods that had be built in questionable areas like in-filled wetlands. Houston’s sprawl and lack of land use planning was criticized as being one reason the hurricane was so disastrous.

Urban planners and transportation experts are already thinking of policy measures to reduce the likelihood that AVs help sprawl spread. At a recent 3 Revolutions Conference hosted by the Institute of Transportation Studies UC Davis, some presenters suggested “pricing mobility” as a way to limit sprawl. “Pricing mobility” would involve taxing “VMT [vehicle miles traveled], vehicle size and incentivizing increased vehicle occupancy” (pg. 3) This pricing scheme could work whether cars were personally owned or temporarily rented. Assuming AVs were treated like a ride-sharing service, riders could pay for the VMT as part of their rental fee, receive discounts if they ride with others (like what happens with UberPool), and have a higher base rate if they request a larger vehicle. Assuming AVs were private vehicles, these policies would simply raise the percentage of total costs imposed on society that vehicle owners would pay – it would not necessarily raise the total cost of cars (whether AV or human-driven) but would simply shift more of the total cost burden onto the person benefiting from the vehicle, rather than continuing to have society grant drivers enormous subsidies.

Differing costs to society; the exact numbers might change with AVs (like a potential reduction in accident risk) but cars are still the most expensive form of transportation.

AVs will reduce the human labor costs of driving, with outcomes that are both positive and negative. On one hand, it could improve the lives of individual people like Ms. James who commute 80 miles out of necessity because they cannot afford to live closer to their jobs. On the other hand, the potential societal costs of AVs include more and more sprawl, which can hurt society economically and environmentally. (Even if AVs are electric and so might be less carbon intensive, very low density development like urban sprawl would still hurt the environment by consuming land and resources that might otherwise be left alone.)
Charlotte Leis
Urban Studies