The Baby Boomers are the first generation to “sprawl”- that includes the size of their homes, their travel distances to work, their car ownership, and even their waistlines!

Now there is concern that autonomous cars (self driving) will make sprawl even worse. A recent story in the WSJ, for example, speculates whether the savings from not owning a personal car will benefit Millennials will want to escape their cramped urban apartments for “bigger spreads, further away.” (Note: the full article presents both pros and cons).

There are several reasons to challenge the future relationship between driverless cars and urban sprawl. A simplistic answer is that if  “hands-free”  was the key factor, then millions of American commuters would already be taking the bus or train to reach their far-away homes. But, generally they don’t. It is estimated that ‘only’ about 600,000 Americans have extreme commutes of at least 90 minutes each way. 

CITIES AND SPRAWL

There are vital reasons why the “extreme commute” may not happen, even when autonomous cars come to market:

The first reason is that cities are going to be better places to live and they will offer a better lifestyle than today. They will be less car-centric and there will be fewer reasons to own private cars. Cities will also become safer for other transport modes, like walking and biking, since autonomous cars are programmed to obey the speed limit and stop signs. Most importantly, they bring new opportunities to repurpose parking spaces and parking lots. This transformation might be a boon to real estate developers and should increase the green-space, as well as the supply of urban housing.

The Baby Boomers are a cohort that enjoy car-travel, and they have matured  along with an auto industry that has became more reliable and affordable over time. This contrasts with younger generations, who have been weaned on computers, and lean towards life styles that are less car-centric. No one has quite nailed what this means to a cohort of Digital Natives, but there seem to be agglomeration effects. Instead of spending a leisurely afternoon driving to the out-of-town outlet mall or golf course like Boomers, Digital Natives might be more inclined to meet up at a local dive and then take short trips together around the neighborhood. So, while autonomous cars could take them “further” their choices might be closer.

COMMUTE  BUDGETS, TIME BUDGETS

The second reason to question the wisdom of long commutes via autonomous cars is more technical. It is associated with “commute budgets”.  As the term implies, people have fixed resources or  “budgets”; they generally do not exceed one hour of commute travel time per day. This axiom is associated with a transportation researcher called Yacov Zahavi. Athough Zahavi’s work was done in the 1970s and 1980s,  he discovered  across different cultures, and different geographic zones, people did not generally exceed the commute budget. It was something like a law of nature.

(Note: Zahavi observed, before Bus Rapid Transit (BRT), that commuters were unlikely to switch from cars to public transit because of the time-tradeoffs.)

In the future, long distance commuters could exceed the one hour “commute budget”, if travel was done with autonomous luxury and autonomous speed. That is the fear. But, one of the main deterrents is that this travel budget then bumps up into the daily “time budget” which is still fixed at 24 hours.  When commuters spend more minutes per day traveling to and from a distant suburb, they forfeit time spent on other activities.  Instead of sitting in a vehicle, people might prefer to do things such as coach their kid’s soccer game, go to the gym or get on  a bicycle for exercise, and even participate in person at civic activities (think bowling alone). So, while the autonomous car may let people continue to text or work while they travel and perhaps even be VR at the soccer game, it will not substitute for participating in real activities.

Beyond the travel time budget and the 24 hours activity-time budget, there is a third resource constraint: Almost all households maintain a transportation budget. In the U.S. today, the average household spends about 29 percent of its income on travel expenses. While the marketplace has yet to set a rate of “cost per mile” for autonomous travel, longer travel will cost more and potentially tip the economic balance between housing and transportation expense. It will also be subject to state and federal taxes, akin to the tax on gasoline today.

TRAVEL AND HAPPINESS

The third factor that will suppress excessive travel has to do with “happiness”. Even if autonomous cars could bring longer commute trips to more distant homes, travel is a derived activity-it is what “we do” to do something else. There is an interesting subset of research correlating wellness, happiness, and travel time.  Joe Cortright at City Commentary  reports on the literature between quality of life and daily commute time. Behavioral economists find that time spent commuting has the lowest positive rating of all daily activities. Longer commutes are also associated with a high incidence of obesity, back pain, and other health impacts. Even if your autonomous vehicle was super comfortable, these human impacts might continue to plague the trip.

SPRAWL NOT?

Note that the behavioral impacts come from the time spent in the vehicle, not necessarily the traffic. Time budgets are complicated. So, one of the unusual findings from the behavioral research is that more traffic congestion is NOT negatively related to people’s sense of well being and satisfaction.  While this needs further investigation, it is a clue to the future. Perhaps autonomous cars will not help people flee the city.

People generally see some benefits to being in a place congested with traffic- think getting to/from a sporting event, rock concert, school travel, or airport. It is all about being social- not about trekking long distances to reach a greener pasture. The Digital Natives may have already discovered that, and are far ahead of other generations.

Meanwhile, urban settings of the future will appear very different when residents can be comfortable and safe transversing on foot or bicycle, but also be able to seamlessly summon a vehicle on demand. Since the future cost for this transportation has not been established, we do not know the economic constraints (think transportation and time budgets). But, we do know, that people  contemplating long commutes still have to wrestle with a 24 hour time budget, at least for now.