Are Mobile Phones Making Us Travel More Efficiently?
Last week, I read an analysis prepared by the Port Authority’s chief economist looking at passenger travel across the Hudson River from New York to New Jersey. As the graph below shows, essentially more than 20 million annual passenger trips into New York City from New Jersey that used to happen in cars, now happen on transit — in the span of just 6 years.
In many ways, this evidence validates what many have been saying — that the fall in VMT nationally has been driven by greater use of transit, an a preference for more urban housing especially among young people. Much of what you see in the graph above has to do with rapid development in the rail-served counties of northern New Jersey (such as Hudson County, where I live). But it’s a hard argument to buy on a larger scale, since the VMT drop has occurred all over the country, not just the region with the nation’s most transit-accessible jobs.
As I though about this over the weekend, I began to think more broadly about the VMT decline — and the fact that a decade in, the transportation research community still doesn’t have a compelling theory or evidence base to explain it. A lot of explanations have been put forward — gas prices, economic stagnation, student debt, changing consumer preferences, etc. — some have been dismissed, others have been justified to varying degrees. But nothing seems satisfying, and nothing seems to really guide what we should be doing.
I still think the economic case is compelling, despite evidence to the contrary. But there is definitely some weird stuff going on. As the graph below shows, the start of the drop in VMT both preceded the per capita GDP drop triggered by the recession, and has continued despite a recovery in per capita GDP. (Though its likely that those per capita gains do not reflect a broadly shared recovery but one disproportionately going to the top earners.)
One could argue that the graph below — the U.S. labor force participation rate — is all you need to explain the drop in travel demand. The share of the U.S. population going to work each day is down about 5% since the Lehman Brothers implosion in 2008.
Per capita VMT is down about 5% off its 2004 peak as well. Which makes sense alongside the labor force participation data. If 5% less of the population is going to work, then we’d expect total VMT to drop by a corresponding amount, all other things considered equal. (Setting aside for now that work trips are only a small share of total travel in the U.S.)
But I’m not an economist, so I decided to leave the analysis there and go back to another hypothesis I floated last year — that the mass adoption of personal navigation devices might be a factor. Were people simply getting fed more direct routes to their destinations on a frequent enough basis to show up in the aggregate demand?
I asked myself point blank — “What changed in 2004 in American society?”
And that question made me think differently about what technologies might be having an impact on travel behavior. What if it wasn’t mass adoption of personal navigation technology that mattered, but rather the mass adoption of personal communications? As Eric Goldwyn argued recently, the smart phone is the most important transportation innovation of the decade. But what if the simple “feature phone” (e.g. voice and SMS only) — once it became more or less ubiquitous throughout the population — started allowing us to coordinate our movements more dynamically and efficiently, resulting in fewer wasted trips?
I started to wonder — if it were true — what would the tipping point for mobile phone adoption be that really started to turn that VMT growth curve back down? 10% 20% 50%? Well, here’s the data, and it kind of blew my mind, because it was in 2003 that more than half of Americans (on average) owned a mobile phone for the first time (55%), and the first time that the number of mobile phone subscribers exceeded the size of the labor force — which I take as a proxy indicator that mobile phone use was more or less universal for all U.S. workers at that point.
Is the mass adoption of mobile communications what’s driving the decline in VMT? A lot of research is clearly needed — the decline in VMT is being driven by a complex intersection of forces — which appear to be reinforcing each other. But I suspect that this technology is playing an enormous role in enabling people to put together alternative mobility strategies to private vehicle travel, or to use their cars more efficiently. And every time I remember that the sunk capital in our mobile phone networks is about what we spent on the Interstate Highway System (about $500 billion in current dollars), it reminds me that transportation planners need to take the impacts of these technologies far more seriously than they do now.
