Why congestion pricing will always be unpopular

By Felix Salmon
October 19, 2011
Down's Law of Peak-Hour Traffic Congestion, has been known since 1962; new research shows that it's true even more generally than previously suspected.

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Traffic expands to fill the space available. This is known as Down’s Law of Peak-Hour Traffic Congestion, and has been known since 1962; new research shows that it’s true even more generally than previously suspected.

Increasing lane kilometers for one type of road diverts little traffic from other types of road. We find no evidence that the provision of public transportation affects VKT. We conclude that increased provision of roads or public transit is unlikely to relieve congestion.

Eric Jaffe draws a simple conclusion from all this:

Whenever a driver shifts onto public transportation, another one quickly grabs the open lane. That leaves just one solution to the traffic problem plaguing American cities: congestion pricing.

“We cannot think of any other solution,” says Gilles Duranton, the paper’s co-author. “As soon as you manage to create space on the road, by whatever means, people are going to use that space. Except when people have to pay for it, of course.”

I’m a fan of congestion pricing. But I’m also realistic about it, and the fact is that for all Jaffe’s enthusiasm, congestion pricing has its own Down’s-like characteristics. Jaffe raves about the “success” of congestion pricing in London and Stockholm, but the only chart he provides gives numbers for the trial period in Stockholm. If you go looking for recent data on traffic in London, Stockholm, or other cities with congestion charges, it can prove surprisingly difficult to find.

Here’s Jaffe, again, quoting Duranton:

“My feeling is, yes, people tend to be against it before they see it at work,” says Duranton. “They think it’s going to cost them more money, which directly it will, but they’re all very unclear about the benefits; i.e. traffic is way more fluid, way faster, and pollution is going down.”

There’s another way to look at this phenomenon, though. When congestion pricing is first introduced, people recoil against it — they expend quite a lot of effort to avoid the charge, and traffic goes down. Over time, however, it becomes just another part of the cost of driving, along with gas and insurance and parking tickets. As that happens, traffic goes back up again. Congestion-charge revenues go up too, of course, and those can be reinvested into public transport.

But traffic is like water — it wants to find its own level, which tends, in cities, to be maximum capacity. If you want to implement a system which keeps traffic below maximum capacity, then you need to apply significant pressure on drivers to keep them away from the roads. And that means not just implementing a congestion charge, but also regularly increasing the amount of the charge over time.

This is how the Singaporean congestion-charging system works. Think of a shutter-priority camera: you set the shutter speed, and then dial the aperture so that the exposure is correct. In Singapore, they set the amount of traffic they want, and then dial up the congestion charge until they get it. It’s much the same idea as the one behind SFPark: you set the number of empty parking spaces you want, and then dial up the parking-meter pricing until you get there.

But the point in all of these cases is that the charge has to be variable over time — specifically, it has to increase over time. Without those steady increases, drivers become inured to the congestion charge, and traffic will go back up to its former level.

As a result, drivers are pretty much never happy with congestion pricing. Either it’s painfully expensive and going up in price — expensive enough to keep them from driving — or else it doesn’t have much effect.

That doesn’t mean that congestion pricing isn’t good public policy. It is. But it’s always going to be unpopular with a powerful constituency. (Drivers, in nearly any city you care to mention, tend to have a disproportional amount of political clout.) Local politicians looking for a popular platform will run on reducing or abolishing the charge, or at the very least not increasing it. And so the old fight keeps on being fought over and over again: while increasing a charge isn’t as politically difficult as introducing one, it’s still tough.

This is something worth remembering when urbanists start waxing utopian on the subject of congestion pricing: once it’s introduced, the fight isn’t over. It’s never over. And if you leave a system long enough without increasing its price, its efficacy starts declining dramatically.

25 comments

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I don’t find this explanation (drivers inured to congestion fees) plausible. Given a congestion target, prices might go up for lots of reasons – population growth, economic uplift making cars more affordable or fees rationalizable, etc. The “painfully expensive” vs. “ineffective” dichotomy feels false.

Regarding political approaches, this is routinely botched. Congestion fees shouldn’t represent a new tax. They can easily be made revenue-neutral by tying them to a tax break; that gets you a constituency *in favor* of the proposal. People don’t broadly support tax increases to fund public transportation, so why would you anchor a congestion pricing proposal to something like that? (I know why you’re tempted to, but it doesn’t make it good policy or politics.)

Posted by absinthe | Report as abusive

I think there is also a plausible explanation for rational, structural reaction to congestion pricing though. People could make adjustments to their commuting behavior that are structural to reduce the cost of the charge- arranging ongoing carpools, buying commuter train passes, arranging for a permanent shift in work hours… There is also the issue of how much traffic is caused by commercial vehicles that might have a relatively lower cost of shifting time. My frame of reference is the SE Expressway in Boston though, so it might not have the same issues everywhere.

Posted by tuckerm | Report as abusive

I’m very much against congestion pricing. Everyone needs to get from place to place but you’re right, making driving more expensive will deter a segment of drivers from getting on the road. Who are the people that will be deterred? Those that can no longer afford to, aka the poor. I get as annoyed as the next guy at congested traffic but I’d rather my commute have to take longer than know that the reason I’m able to zip along is that the poor are getting priced off the road. But hey, that’s just me.

Posted by spectre855 | Report as abusive

There’s another possibility– the policy Which Dare Not Speak Its Name– reduce the space devoted to roads. I.e., since you can’t decrease congestion, use congestion to force people to use alternative modes of transportation. If you read ‘urbanist’ proposals carefully, this is actually what many of them are saying. But, of course, they can’t actually say that out loud.

Posted by MattF | Report as abusive

Congestion pricing is unpopular because it is one of those 1% rules, where people with money get to make decisions of access, despite everyone paying into that tax that paved the way for the asphaltic concrete.

If congestion pricing is the disincentive to congestion, then reallocating the money people paid to access clear roadways should be used as an incentive for everyone else to use public transportation. One could indirectly pay the rest of the public to use public transportation, by lowering the cost of usage during peak hours.

Posted by GRRR | Report as abusive

I’d think that congestion pricing, if it was set at a high enough level, would become sufficient to subsidize public transit. The subsidy could be spent on making transit more pervasive (more routes at higher frequency), and less expensive to use, thus making public transit a more attractive option, and halting the tendency of people to backslide towards driving.

Posted by Auros | Report as abusive

There’s another possibility– the policy Which Dare Not Speak Its
Name– reduce the space devoted to roads.

This is only a policy that dare not speak its name in the US. There are cities in Europe where a version of it is official and implemented. Zürich, for one, is consciously traffic hostile. Reduced parking space, no synched lights, closed roads, etc., etc., and an conscious planning interest in making urban driving unpleasant.

Posted by seanmatthews | Report as abusive

There is also a philosophy at stake. Roads are publicly provided essential services. Would it be appropriate to have congestion pricing for the courts of law? After all, they are often congested. And what about when people shift out of their cars into buses and trains and they become congested? Another congestion charge?

There is always the option of closing road space – that’s certain to decrease congestion!

My view is that congestion is a reasonable queuing mechanism, and that urban policy should be directed at providing a balance of incentives between alternative modes of transport based on their cost-effectiveness.

There is not strong argument for or against a congestion charge per se, but as part of funding mechanism for a multi-modal urban transport plan, perhaps it has a place.

My detailed analysis of the topic is here
http://www.macrobusiness.com.au/2011/10/ tax-the-poor-so-the-rich-can-drive-faste r/

Posted by Rumplestatskin | Report as abusive

A Down’s law situation can only exist when the supply of road is _hugely_ under-provisioned relative to demand. Otherwise, peak congestion would indeed ease meaningfully after road capacity is increased.
So we have a public good that people are crying out for and your preferred solution is to: not to supply more, but add fees so that those in the money can nevertheless still get what _they_ want. Go OWS!
Congestion is wrong as a metric to optimize or target, and congestion (as interpreted in Down’s law) is simply not “the traffic problem plaguing America”. If you disagree, here’s a puzzle for you. In the face of Down’s law, would you recommend that from now on we only build one lane roads? By the “law” we can’t ease _congestion_ by building roads any wider, so why not just save all that money in the first place?

Posted by bxg6 | Report as abusive

Congestion Pricing rules. Yes it pushes poor off the roads but all of society benifits via the transition to mass-transit.

I hate paying tolls but I hate traffic more.

Posted by y2kurtus | Report as abusive

I think the thing that bothers me most about this idea is that there are only two parties. Those that have enough money and will get a great benefit out of more convenient driving and those that do not have enough money and will be deprived of a fundamental need. I’m all for making driving more inconvenient in congested areas, but I’d rather not prioritize the convenience based on wealth.

Posted by spectre855 | Report as abusive

> I’m all for making driving more inconvenient in congested areas, but I’d rather not prioritize the convenience based on wealth.

Wow! This is a stupid comment. Bottom line, prioritizing based on ability to pay is economically efficient. Assuming we all have the same income (*), this is the right way to encourage us to only utilize this limited resource when we really really need to.

(*) We don’t? Let’s hand-wave that away as a triviality. Modern economic modelling only works if we all have similar incomes and utilities, so let’s not let real world fairness get in the way of the plutocrats or (even more importantly) “clean” fresh-water economic modelling.
Just accept their assumptions. And under their assumptions, your comment is silly. In the real world? You aren’t permitted to comment about the real world.

Posted by bxg6 | Report as abusive

Build it and they will drive has been true since la Via Appia and the dreaded chariot jams at exit VIII into Rome.

Bxg6 is right, though a tad abrasive. Lowering road usage pricing to the lowest payer (i.e. someone with no income) means eliminating it altogether. Continually raising usage fees is a progressive tax since poor drivers are forced onto public transportation and only the rich end up paying road fees.

The major problem is that governments, despite their honesty, competence, and fiscal integrity, don’t always use the road fees as promised, which is to say in improving and subsidizing public transport.

Given the state of the London Tube and its extortionate prices, it is clear that the poor have been chased from the roads and herded into the Tube and onto buses to be shorn and milked. Other cities have more reasonable public transportation, notably Paris and Singapore, though the latter’s system is far from complete.

Posted by Expat64 | Report as abusive

bxg6, haha, it’s too early in the morning for that kind of sarcasm. I had to read your comment several times before I caught the facetiousness.

Posted by spectre855 | Report as abusive

Good for you, Felix, for your willingness to question orthodoxy — in this case yours and mine (if I may) in favor of c.p.

Yet your conjecture that “Over time [the congestion charge] becomes just another part of the cost of driving” is unproven. I don’t believe it’s been the case in Singapore or Stockholm, though I share your concern and frustration over the lack of clear-cut up-to-date data from London.

The current status of c.p. in all three cities is definitely worth looking into, as is the larger behavioral question of how people respond, or don’t, to different ways of delivering and experiencing prices and costs, and how their responses change over time.

Still, it stands to reason (at least I believe so) that raising the average price of a round-trip to the Manhattan Central Business District from, say, $30 (gas, some tolls, parking “where applicable,” etc.) to $40 (with a $10 congestion charge) will lead to a sizeable *permanent* reduction in the number of trips. The congestion charge may indeed become, “over time … just another part of the cost of driving,” but drivers will be mindful of the higher cost, all the same.

Posted by Komanoff | Report as abusive

Traffic expands to fill the space available. This is known as Down’s Law of Peak-Hour Traffic Congestion, and has been known since 1962; new research shows that it’s true even more generally than previously suspected.

Only if the new space is nowhere near enough for demand, and/or is underpriced.

Increasing lane kilometers for one type of road diverts little traffic from other types of road.

Only if there is a shortage of both freeways and surface streets. If there is plenty of one it can and often will be used as a substitute for at least some trips that would have used the other.

We find no evidence that the provision of public transportation affects VKT.

Because the Onion was right: *no one* rides public transport if he can drive. Voters only ever support it in the hope that others will be forced to use it.

We conclude that increased provision of roads or public transit is unlikely to relieve congestion.

That is like saying that the famine in Ethiopia in the ’90s proved that growing more food does not relieve famines. It was true in their case, because the famine was deliberate on the part of that country’s government, and when Eritrea won independence, the problem went away. If we can make the industry of providing transport facilities similarly independent of government here, I predict that our congestion problem will go away too.

Eric Jaffe draws a simple conclusion from all this:

Whenever a driver shifts onto public transportation, another one quickly grabs the open lane. That leaves just one solution to the traffic problem plaguing American cities: congestion pricing.

It’s certainly the only solution he’ll see as long as he wears those blinders.

[snip]
There’s another way to look at this phenomenon, though. When congestion pricing is first introduced, people recoil against it — they expend quite a lot of effort to avoid the charge, and traffic goes down. Over time, however, it becomes just another part of the cost of driving, along with gas and insurance and parking tickets. As that happens, traffic goes back up again.

If it were true congestion-pricing, the authority would then immediately raise the price and keep raising it until traffic is once again driven down to a level where driving is comfortable.

Congestion-charge revenues go up too, of course, and those can be reinvested into public transport.

Gag! Nothing government spends our money on is an “investment”. And that goes double for public transport, which everyone knows is a waste of money.

If government wants to implement congestion charges without being rightly seen as commuters’ sworn enemies, these revenues MUST be used to ADD ROAD CAPACITY. (And don’t tell me there’s no room, at least until you have stacked up multiple decks of streets, like those in Chicago’s Loop district, higher than the buildings they serve, with parking structures to match.)

But traffic is like water — it wants to find its own level, which tends, in cities, to be maximum capacity.

Because road capacity, so long as it’s free, is a public good and therefore too little is created — and governments don’t change that fact.

If you want to implement a system which keeps traffic below maximum capacity, then you need to apply significant pressure on drivers to keep them away from the roads.

Or you need to get out of the way of entrepreneurs who would provide as much road capacity as drivers demand. Thus leaving ordinary people with all the choices we’re used to having, and are entitled to keep forever.

I know which sort of society I’d rather live in. So do all true Americans.

Cross-posted to the list
http://groups.yahoo.com/group/Preserving TheAmericanDream/ . I suggest followup posts go there.

Posted by jdgalt | Report as abusive

Your system is broken. It took out my formatting and quoting.

Posted by jdgalt | Report as abusive

This is nonsense. The author complains that there is no data on London and Stockholm then he asserts in the absence of data that over time “traffic goes back up again.” Prices allocate goods all across the economy and no one is saying that congestion charges won’t change over time like all other prices.

Posted by mcden | Report as abusive

As someone who lives close to London and regularly travels into the city I think the congestion charge is a fantastic thing.

The reality is that the charge does not hit the poor (because they weren’t driving a Bentley or Rolls-Royce into central London on a Thursday afternoon in the first place.) It hits the rich who want to do something that is in their interest but against the interest of everyone else.

Typical Londoners or travellers to London do not drive. Now the roads are far less crowded for the buses that these people do travel on.

Obviously this isn’t necessarily representative, but I don’t know anyone who actually lives in London who thinks the congestion charge isn’t good. Remember that highly efficient cars are exempt, as are people who live inside the congestion charging zone.

Providing the alternatives are viable (and in London, with the Tube and buses they are) the congestion charge works very well indeed.

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