I’m not talking about the controversial computer game of my childhood, but about the closure of the 405 in Los Angeles for 53 hours. The predicted massive traffic jams failed to materialize, just like every time there’s a closure due to construction, an accident, or an earthquake. The reason is that traffic engineers and planners, the media, and even airlines talk up the possibility of gridlock so much that people choose to stay home or use other modes of transportation. The Huffington Post’s warning that the closure could actually increase carbon emissions because people would take longer detours or cause more traffic jams failed to materialize.
Although normally the induced demand phenomenon is more in the long term than in the short term, if the closure is known to take a very short time, then people can make short-term behavioral changes. They’re not going to move closer to where they work or agitate for better public transit, but they’re going to move non-essential trips to another day, carpool or take transit or bike just the one time, or even sleep one night at the office. Indeed,
Dennis S. Mileti, a sociologist, has spent his career analyzing human behavior around natural and man-made disasters. He advises everyone from the Department of Homeland Security to hazmat workers on how to deliver effective warnings that make people pay attention without panicking and guide them to take precautions and other appropriate actions.
In this case, he said, the message got through because of the blanket of media coverage.
“The public doesn’t change its behavior on its own,” Mileti said. “It behaves on the perceptions formed by the information people are provided.”
Ironically, transit strikes do lead to worse traffic, even in Los Angeles. It’s not because transit is more significant to the population of Southern California than the 405; although more people ride transit in Greater Los Angeles than take the 405 across Sepulveda Pass – about 1.2 million per weekday vs. 500,000 – the transit ridership is much more dispersed, and is dominated by people who can’t afford to drive alone. Instead, the issue is one of media forewarning. Strikes are sudden, and even when they’re threatened, the media focus is never about mitigating the extra traffic, not even in New York.
Potentially, this may be one reason why in the long term, building more roads creates induced demand, and demolishing them causes demand to disappear. Highway openings are widely advertised: politicians love ribbon cutting ceremonies, and the media runs stories about developers and drivers complaining about traffic on parallel roads. Highway closures are more sudden – the two test cases, the Embarcadero Freeway and the West Side Highway, were caused by disaster – but afterward the media coverage and the short-term spike in traffic teach the public that those highways do not exist, leading the traffic to vanish.
Of course, reduced demand isn’t just trips vanishing into thin air. Some trips do get diverted to low-traffic side streets. Others get diverted to mass transit, just as the original construction of the Interstates destroyed transit ridership in the US. Slate has an article about how Carmageddon is teaching the locals that mass transit exists in the first place; it’s possible that it’s going to lead to a long-term increase in ridership, just like short-term spikes in gas prices.
This does not mean long-term road use is going to decline – in fact, it’s going to increase because of the added capacity on the 405. Although the construction of rail transit leads to a reduction in traffic (P.S. if you follow the link, bear in mind its pollution estimates are really low,
coming from among other things only counting global warming damage to the US), this assumes business as usual. The main lesson here is not about transit, but about what Los Angeles can expect to happen if an earthquake forces the 405 to be permanently closed, just like the Embarcadero. Although drivers and many business groups are guaranteed to warn about traffic, in reality if such a disaster happens, high traffic will not happen, not in the long run.
Update: as Herbie notes in the comments, St. Louis closed a segment of I-64 for two years, and not only did predicted congestion barely materialize, but also the economic impact of the closure according to business surveys was zero.