Debunking the "building roads causes congestion" myth

For some time now transport policy has been influenced (and in some countries dominated) by an ideological branch of the sector which could best be called "planning environmentalists".  This group has the following set of views, which are based more on philosophy and politics, and rather less on evidence:

- The problem with transport is people driving;

- Helping cars move is a negative because cars kill, cars pollute and cars take up a lot of space;

- Building new roads magically induces more car trips, so roads shouldn't be built, in fact in some cases they should be closed (the busiest ones);

- People are "dependent" on their cars, rather like drugs, but they would rather not be, they would rather use public transport if only the choice was there;

- Travel by public transport is good, the more the better;

- Travel by rail is almost nirvana, it is the safest, least pollution, can carry the most number of people, can be easily powered by electricity.  The more of this, the better we will be;

- Where railways can't even start to remotely seem sensible, light rail (trams) are the next best thing.  Cheap trains at street level.  People love them, the more the better;

- When even light rail is insanely expensive, buses are ok, but they are only ever a stopgap (after all they have diesel motors, use rubber tyres and um roads);

- Cyclists are important too, except when they disagree with light rail;

- Walking is important, but please don't talk about people who walk or bike who might be attracted to highly subsidised public transport - because that can't ever be a bad thing;

- Freight movement in cities is largely ignored because despite the best will in the world, it can't be moved by rail in any great volume.  Freight benefits from public transport though;

- Public transport relieves congestion, except it doesn't, but actually what we mean is it doesn't actually matter.  Congestion is a good thing, it is a tool to encourage people to use public transport (A Green Party policy advisor told me this himself);

- Road pricing is fabulous, but only to penalise cars.  All the money collected should go to subsidise public transport;

- Road users should pay the full costs of their infrastructure and externalities and pay for public transport subsidies, public transport users should pay a small fraction of the operating costs of their services, or even nothing at all, for they do us good by riding around on those trains;

- Public transport would be more viable if cities were higher density, like Prague, Moscow, Zurich, Barcelona, London.  People should live in high density housing more, less in suburbs.  Planning rules should enforce this, then people could live in tighter communities, travelling by rail, which of course, is what they really want, if only they knew better.

A key part of the dogma behind this, which is wholly embraced by the Green Party, is the notion that if a new road is built, it will become congested within a few years, making the whole construction futile.  It is the only sector where a claim is made that when something is popular, it is a bad thing.  It always ignores whether the road has been priced properly of course.

The Washington Examiner has an excellent article summarising the history behind the claim that building road causes congestion, and the countervailing evidence.  A good example is Phoenix, Arizona:

in the real world, adding highway capacity can prove quite helpful. The Texas Transportation Institute’s annual Mobility Report, for instance, demonstrates an uncanny correlation between capacity and traffic congestion: Areas that add capacity tend to have lower levels of congestion. And induced demand doesn’t always -materialize. Take, for example, the city of Phoenix, a town built with almost no freeway system.

As a result, the Phoenix metro area historically had some of the worst congestion in the nation. Between 1982 and 2007, Phoenix decided to build the highways it should have had in the first place.

They added so much asphalt that, according to the research firm Demographia, the city’s highway-lane-miles per capita grew by 205 percent. During that period, highway-vehicle-miles-traveled per capita increased by only 12 percent. And, like magic, traffic congestion plummeted.

Now what is true for Phoenix may not be true for Philadelphia. And building highways almost certainly induces some demand.

In New Zealand you can see the same, with plenty of examples to prove that building roads need not lead to congestion.  In Auckland, Te Irirangi Drive was built some years ago and has yet to be even close to capacity.  The south eastern highway from the Southern Motorway to the Pakuranga Motorway likewise (despite being built on the cheap).  In Tauranga, toll road Route K is now locally infamous for losing money because of lack of demand, and the related route J north isn't remotely congested.   Wellington's motorway bypassed Tawa  in the 1950s, and neither the motorway nor Tawa are congested.  Upper Hutt has also been bypassed with a sustained reduction in congestion through that city (and on the highway).  Lambton Quay used to be gridlocked at peak times with cars in the 1970s, until the motorway provided a bypass to south of the city.  Nelson's Stoke Bypass has not resulted in congestion in Stoke or on the highway.  

Now when a new road opens up a previously inaccessible, but desirable location, then it will have rapidly increased demand.  New crossings can do this, like the Auckland Harbour Bridge which needed a duplication of capacity within a couple of years of opening.  Tauranga Harbour Bridge was similar, but only when the toll was removed (which moderated demand).   In addition, piecemeal upgrades to a road that eliminates one bottleneck, but doesn't deal with one further along the route can exacerbate congestion at the further bottlenecks (but doesn't destroy the case for relieving congestion for those who do not go that far).

Modern cities throughout the world have used road building as part of their strategy to meet transport demand.  Where they have failed is in unfettered construction that means a subsidy from those who don't use the road for those who do.  In short, without using the market tool of pricing, building new roads can simply be just another subsidy.  

In New Zealand at the moment there isn't any appreciable use of pricing to manage demand to meet supply, but there is a major road building programme - one that does involve a considerable subsidy to road users in particular parts of the country (Auckland and Wellington mainly).    A more commercial approach may not build so much, and certainly not so fast.   Sadly, the main choices in policy offered to voters are to embark on grand Think Big road projects (e.g. Transmission Gully and the Puhoi-Wellsford motorway), or to embark on grand Think Big rail projects (e.g. Auckland underground rail loop and Auckland airport railway).   Actually letting users decide with their dollars seems something neither the Nats or the Greens can get to grips with.