“We are creatures of habit. So what happens when our driving habits are thwarted?
Apparently, we learn new habits.
David Levinson works in the department of civil engineering at the University of Minnesota, so he pays attention to such behavior. The Interstate 35 bridge failure offered an unexpected opportunity to study drivers.
Before the collapse, the bridge handled 140,000 crossings each day, he said.
‘After the collapse, we [City of Minneapolis, Hennepin County, MnDOT] counted traffic on other bridges and were at about 90,000,’ he said. ‘So 50,000 people decided they didn’t need to cross the river anymore.’
Levinson said that an industry rule-of-thumb is that one-third of drivers will take an offered detour, while others will seek their own routes or change their routines.
Once the new bridge opened, ‘a lot of people didn’t switch back, either because their new route was maybe as good, or they’d just developed a new habit,’ he said.
People don’t always take the shortest path somewhere, he added, which helps explain those who veer out of a traffic jam onto side streets in search of a route that, even though longer, lets them keep moving.
So what’s worse? Winter or road construction? It depends.
‘In the case of winter, everyone is affected, but for a short duration until the roads are cleared,’ Levinson said. ‘Road projects affect a small amount of people, but for a long time.’
Bottom line: ‘People are happy when the road is fixed,’ he said. ‘I don’t know how happy they are that the road is being fixed.’
The transportation sector is rife with technology/policy mismatches. We often seek new to develop or deploy technologies to solve what are ultimately policy problems; and we often try to implement policies to solve what are ultimately technical problems. Attaching the correct domain to the problem is the first step in solving it.
As an example of the first, consider any transportation investment aimed at expanding capacity to address congestion. The policy failure here is the lack of peak-period pricing (and secondarily location-specific pricing) that would ration scarce capacity. Instead we move to a ‘predict and provide’ mode, and where we fail to provide, we ration by queueing. Whether or not we should build a project to expand accessibility from a place, we should not expand capacity to expand accessibility only at a given time-of-day until we have properly priced the network, so that travelers consider the externalities they impose and pay the full marginal costs of their trip.
The best illustrations include your typical freeway widening. A widening by definition just expands capacity (which is only relevant in the peak hours), and does nothing to expand accessibility during the rest of the day, since no new places are connected. The road may very well be congested, which is what you would expect when you give something valuable away at below marginal cost. The capacity expansions often don’t have the desired effect on congestion reduction due to induced demand in the short run, and induced development in the longer run.
Transit projects are often billed as “congestion reducing”. This is the one of the worst reasons to invest in transit. It is as if we said a new highway reduces crowding on the bus or the bike lanes. Transit investments should be justified by the benefits they provide to existing and new transit users, not on some marginal third-party actor. Yet we see this claim allthetime. [I know, the claim is marketing to induce non-users to see a benefit for the enormous subsidy they are providing, but it is intellectually dishonest]. I won’t say there is never a highway congestion reduction by-product, as if the project does gain new riders, at least some of them may have otherwise been driving a car during peak times, but that is a third-order effect that often does not appear in the traffic statistics.
As an example of out-of-sync policy approaches to technical problems, consider emissions reduction. Automobile emissions are a problem for many reasons, not the least of which is public health. Emissions can be thought of as a logical chain of calculations like this:
The land use and transportation planning side of things (policy) tries affect behavior to reduce number of vehicle trips and average trip length. The technology side of the equation tries to improve fuel efficiency and reduce pollution per unit of fuel burned. There are policies that can encourage the development of the technology (CAFE standards) and technologies which can reduce average trip length, like elevators and skyscrapers. But the opportunity to practically eliminate emissions can only come from driving one of these numbers to zero.
My bet would be that it is far easier to change the power plant on the fleet (through electrification), and the pollutants per gallon through more efficient combustion if you continue to burn liquid fuel, than to get number of motor vehicle trips or trip length close to zero. In the US, we might be able to take baby steps towards behavioral change, but we are starting from an existing built environment, an existing economic make-up, and existing transportation networks that took a century to build and will take a century to unwind. We have climbed Mt. Auto, and atop Mt. Auto, Mt. Not-Auto is very distant.
In short I claim the vehicle fleet, which turns over every 10 or so years, is more malleable than land use, which turns over every 50 years, or road networks, which effectively don’t turn over, or travel behavior in the absence of pricing.
This is not to say people should not be encouraged to walk (or bike if masochistic) and locate near jobs if feasible. Similarly, developers should not be needlessly discouraged or prohibited from high densities so long as they internalize costs or pays off the losers. But the reasons behind that are fundamentally private (that is what people prefer) rather than for the good of the environment. Preferences too are malleable, to a point, but reprogramming 300 million individual, customized brains takes time and effort, and the population only turns over generationally.
I walk (even in the snow and ice). There are many reasons people may want to not drive their car, or not drive as much. Personal cost and pleasure are among them. But to promote those policies as serious efforts to address pollution problems, when technical solutions are available is Sisyphean. Induced demand rears its beloved head. A large part of the reductions in VMT from one set of sources will be eaten by another, even if we have macroscopic trends working (very slowly) in a favorable direction, like peak travel.
There are potentially effective travel demand management (TDM) strategies. Pricing (as per above) is the most effective, if only it could be implemented. By all means, impose a carbon tax, but that will have very small effects on overall behavior unless the tax itself is very large.
Sadly, most policies, short of pricing, aimed at TDM have been dismally unsuccessful. Land use changes are slow at best, and there is little guarantee that new development will do much to actually reduce vehicle emissions, most people don’t work or live on site, and new transit oriented developments are not in dense environments to do enough to enable people to forego much auto travel.
Similarly, improving the efficiency of roads (transportation systems management or TSM) through strategies like improved signal coordination and ramp metering are modest in their gains.
This is the classic hammer/nail conundrum. Some people want to help save the world. This is a wonderful and potentially socially-productive endeavor. Yet, their only tool is a hammer. Their conclusion is that saving the world is a nail, when it is really a snowglobe. We would be better served by finding nails for the hammer users, and rags for the snowglobe tenderers.
To get meta about this, policies which provide proper incentives can help match the wannabe heroes with the real Penelope Pitstops . Technologies can help with the matchmaking market as well, as has proven so popular in the dating world.
David Levinson, Transportist 
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