Reduced demand: Tolling or restricting cars reduces traffic

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By Joe Cortright

We have urban traffic congestion because we heavily subsidize people driving in cities.

Reducing subsidies and lowering road capacity reduces traffic and congestion.

Why are we building highway capacity for users who won’t pay its costs at 90 percent discount?

By now, we all know about “induced demand” the idea that when we build more road capacity (ostensibly to reduce congestion) we simply prompt more and more people to drive. Well, it turns out the reverse is also true:  If we price or take away capacity, by closing streets to some vehicles or imposing tolls, we actually reduce the level of traffic in an area. Time and again, real world experience shows slashing or pricing capacity reduces urban congestion.

Case in point:  The Miracle on 14th Street. A week ago, New York City effectively banned through-car traffic on 14th Street in Manhattan between Third and Eighth Avenues. This miracle comes in two parts: Part one is the much improved bus speeds on 14th Avenue; once the city’s slowest bus line, the M14 is now racing ahead of schedule, with the added benefit that freed from cars, 14th Street is now a far more pleasant place for people.

Buses are zooming on 14th Street in Manhattan (Streetsblog)

But the second, and in many ways less obvious part of this miracle is on the adjacent 13th and 15th Streets. If you assume that traffic is a kind of incompressible liquid, you’d expect that banning cars on one street would automatically produce gridlock on adjacent streets.  That actually hasn’t turned out to be the case. The adjacent streets are, if anything, less trafficked than before, as reported by the West 13th Street Alliance:
Traffic didn’t divert to nearby West 13th Street (Twitter: @W13StAlliance)

Seattle’s Alaskan Way: Carmaggedon Avoided

City Observatory readers will remember the predictions of “Carmageggdon” made for downtown Seattle when the City finally closed the since-demolished Alaskan Way Viaduct. Part of the viaduct had to be removed before traffic could use the new tunnel, with the result being for a period of weeks, a roadway that had carried about 90,000 cars a day through downtown Seattle was removed, with no replacement.
Instead of gridlock, traffic levels throughout downtown Seattle were reduced. The Seattle Times reported, with a note of incredulity and amazement, that “the cars just disappeared.” By shutting down the flow of traffic from the viaduct to Seattle streets, the closure reduced the demand on those streets and enabled traffic to flow more smoothly.

Things quickly went back to “normal” once the City opened the new SR 99 tunnel to replace the viaduct’s highway lanes.
Here’s the point:  road capacity doesn’t so much relieve traffic as it creates it.  When we reduce the capacity of a system to introduce cars into a city center, we get fewer cars.
But after months of getting a free ride, tunnel users will finally be asked in early November to make a modest contribution to the cost of the project.  The $1 to $2.25 toll that tunnel users will be asked to pay will cover less than 10 percent of the cost of the $3.3 billion in tunnel construction and related costs.
The toll, not surprisingly, is going to discourage some people from using the tunnel.  The Washington State Department of Transportation reportedly expects tunnel traffic to drop by 30 to 50 percent.

Why spend public money on capacity users don’t want?

Reflect for a moment what that means:  Today, as long as the trip is free, about 80,000 vehicles use the new multi-billion dollar tunnel.  When asked to pay less than 10 percent of what it cost to build the tunnel, something like a third to a half of all current users say “it’s not worth it to me.”  In effect, they’re saying, I’ll only use the tunnel if somebody else pays for it. And just for the record, that $2.25 tunnel toll is less than the $2.75 bus fare that King County Metro charges its bus and light rail riders.  That, in a nutshell, is the perverse value proposition that guides so much urban transportation investment in the US: we spend billions on highway capacity that is un- or under-priced, and that people only use because its heavily subsidized, and charge higher prices to those who use more socially and environmentally responsible options.

For the record, the same thing has happened elsewhere when highway users are asked to pay even a modest fraction of the cost of adding road capacity. As we’ve documented, in Louisville, Kentucky, tolls of just $1 each way for a new interstate bridge reduced traffic by almost 40 percent.
The big concern in Seattle again is that the cars that avoid the tolls will clog up other streets. Heather Marx of the city’s transportation department told local television station KOMO:

“During the peak time, there’s nowhere really to go, but we do expect to see more traffic on downtown streets”

But as the miracle on 14th Street in Manhattan, and Seattle’s own experience earlier this year shows is that traffic isn’t so much diverted as it is reduced.

Maybe we should think of highways and major arterials in cities as causes of traffic rather than their solution.  What an urban freeway does, in effect, is point a firehose of car traffic at a city street system. When we reduce the flow of traffic on the freeways in and near cities, we reduce the number of cars traveling to and on city streets.

One other point:  We’re often told that we can’t do anything to reduce car traffic until we dramatically beef up alternative ways of getting around, especially transit. But the lesson here is that car traffic can change quickly, and that reducing car traffic is the fastest and most effective way to improve transit service. Getting cars out of the way makes buses move faster, making them more attractive, and reducing their cost (drivers is more productive, and move more people, more miles if the bus can go faster). No transportation policy is more equitable than one that gets buses moving faster.

Joe Cortright is President and principal economist of Impresa, a consulting firm specializing in regional economic analysis, innovation and industry clusters. Over the past two decades he has specialized in urban economies developing the City Vitals framework with CEOs for Cities, and developing the city dividends concept.

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