Can public transport investment really fix traffic congestion?

Well, this is fine: traffic in the north west Chinese city of Xi'an on a smoggy day. Image: Getty.

Now and then, someone mentions that a particular transit project did not reduce traffic congestion, as though that were evidence of failure.

In fact, the relationship between transit and congestion is an indirect one. In most cases, it’s unwise to claim congestion reduction as a likely result of your proposed transit project. (In this post “congestion” means that volume/capacity ratio for motor vehicles on a roadway is high enough to substantially reduce average speeds.)

Road widening, however, is also not a very good way to relieve congestion, except in the short term. In his 1992 book Stuck in Traffic Anthony Downs described the effect of widening an expressway in terms of a “triple convergence”:

In response, three types of convergence occur on the improved expressway:

(1) many drivers who formerly used alternative routes during peak hours switch to the improved expressway (spatial convergence);

(2) many drivers who formerly travelled just before or after the peak hours start travelling during those hours (time convergence); and

(3) some commuters who used to take public transportation during peak hours now switch to driving, since it has become faster (modal convergence).

Downs is describing only the immediate effect of the road expansion. Further increases in traffic will come from any new development that is attracted to the road’s catchment as a direct consequence of its expansion.

Prof. David Levinson’s work in the Minneapolis / St. Paul region suggests that, while added capacity generates new vehicle trips, the effect is often not great enough to restore the previous level of congestion. However, your results will obviously vary based on the amount of development that occurs as a result of the new or expanded road. If this development adds enough new vehicle trips to fill the new capacity, traffic congestion can return to near previous levels.

So the only way to make the congestion benefit of new road capacity permanent is to severely restrict development in the catchment area of the road – an impossible bar in most cases. In fact, parties who will profit from further development in a corridor may be part of the political consensus in support of a road expansion, even as the same expansion is marketed to existing residents as a congestion reducing project.

Otherwise, there appear to be two broadly applicable ways to relieve congestion in a substantial and permanent way.

Economic collapse. Traffic congestion drops during economic slowdowns, because fewer people have jobs to commute to, or money to spend on discretionary travel. A complete economic collapse, which causes people to move away from a city in droves, is always a lasting fix for congestion problems.

Correct pricing of road space. Fundamentally, congestion is the result of underpricing. If you give away 500 free concert tickets to the first 500 people in line, you’ll get 500 people standing in line, some of them overnight. These people are paying time to save money.

Current, prevailing road pricing policy requires all motorists to act like these frugal concertgoers. Motorists are required to pay for road use in time, rather than in money, even though some would rather do the opposite – and our cities would be safer and more efficient if they could. Current road pricing policy requires motorists to save money, a renewable resource, by expending time, the least renewable resource of all.

So if transit isn’t a cause of reduced congestion, what is its role? Do transit advocates offer nothing in response to congestion problems that have many voters upset?

In fact, transit’s role is essential, but its effect is indirect.

1) Transit raises the level of economic activity and prosperity at a fixed level of congestion.

Congestion appears to reach equilibrium at a level that is maddeningly high but that can’t be called “total gridlock.” At that level, people just stop trying to travel. If your city is car-dependent, that limit becomes the cap on the economic activity – and thus the prosperity – of your city. To the extent that your city is dependent on transit, supported by walking and cycling, economic activity and prosperity can continue to grow while congestion remains constant.

To quite a comment left on my website, on an earlier version of this post: “Toronto achieved significant downtown employment growth without increasing road capacity after the 1960s, thanks first to increased subway ridership and later due to increased commuter rail ridership. Congestion is still bad on the roads and expressways into downtown, even with transit expansion, but the expansion of transit has permitted the downtown to grow beyond what the road network would have supported.” A similar pattern can be observed in many similar cities.

2) Transit enables people who can’t drive to participate in economic life.

Groups who don’t have the option to drive include many seniors and disabled persons, some youth, and a segment of the poor. Providing mobility to these groups is not merely a social service; it also expands participation in the economy.

For example, during the US welfare reform debate in 1994-96, government began raising pressure on welfare recipients to seek and accept any employment opportunity. For the very poor living in car-dependent cities, the lack of commuting options became a profound barrier to these job placements.

This is really an element of the previous point, since all employment, even of the poor, contributes to prosperity. But this has independent force for government because unemployed people consume more government services than employed people do. This benefit of transit should routinely be described in terms of economic efficiency, as I’ve done here, rather than appealing to pity or to alleged “economic rights,” as social-service language often implicitly does. The appeal of the social service argument is just too narrow, especially in the US.

Hey, at least the train is moving: just another rush hour in Manila. Image: Getty.

3) Transit-dependent cities are generally more sustainable than car-dependent cities.

They cover less land and tend to have fewer emissions both per capita and per distance travelled. The walking that they require is also better for public health, which produces further indirect economic benefits in reduced healthcare costs.

4) Intense transit service is essential for congestion pricing.

Congestion pricing appears to be the only effective and durable tool for ensuring free-flowing roads while maintaining or growing prosperity. Congestion pricing always causes mode shift toward public transit, so quality public transit, with surplus capacity, must be there for a pricing plan to be credible.

5) Surface exclusive transit lanes (for buses, rail, and arguably two-wheelers and taxis) improve the performance of emergency services.

This argument should be much more prominent, because even the most ardent car-lover will understand it. Few things are more distressing than to see an emergency vehicle stuck in traffic, sirens blaring. When confronted with this, all motorists do their best to help. But if the entire width of a street or highway is reserved for cars (moving or parked), and is therefore capable of being congested, it can be impossible to get out of the way of an emergency vehicle even if every motorist present has the best of intentions.

Emergency response should be one of the strongest and most obvious cases for surface transit lanes. Motorists understand the need to drop to a low speed in school zones, to protect the life of every single child. Why do we not accept come degree of delay to save a child who may be dying somewhere else, because the ambulance is stuck in traffic?

In the end, of course, “congestion” is not a good measure of the outcomes of transit. In fact, the very notion of congestion presumes a motorist’s view of the world. I agree with another commenter, Rodrigo Quijada, when he writes:

What we’d like to do in a city is to reduce TRAVEL TIMES. Reducing congestion is a way to do that, but in no way the only one. Over the decades, in places where car transportation has become dominant, people have got used to see travel times and congestion as the same thing, thus orienting their thinking and their solutions to reduce congestion. But this is essentially a confusion.

Still, in real-world transit politics, selling transit projects to current motorists is a necessity, and the current motorist is likely to see her problem as one of congestion. So it’s important to be clear on what transit can readily do for her.

  1. It can provide an alternative to driving which may be faster, more cost effective, and less stressful. This argument can be put quite selfishly: Good transit won’t eliminate congestion in your city, but it can eliminate it from your daily life.
  2. Transit helps reduce government spending on social services by enabling transit disadvantaged groups to participate in the economy. This obviously has a range of health and wellness benefit apart from its economic role.
  3. It can increase the level of prosperity at a fixed level of congestion.
  1. Its exclusive lanes protect emergency vehicles from congestion-related delays, potentially saving lives.

Jarrett Walker is an international consultant in public transit network design and policy, based in Portland, Oregon. He is also the author of “Human Transit: How clearer thinking about public transit can enrich our communities and our lives".

This article was originally written for his blog, and is reposted here with permission.


Here’s how Copenhagen puts cyclists at the top of the social hierarchy

A cyclist in Copenhagen, obviously. Image: Red Bull/Getty.

Have you ever wondered why Britain is not a nation of cyclists? Why we prefer to sit in traffic as our Dutch and Danish neighbours speed through the city on bikes?

Forget about hills, rain, and urban sprawl: the real reason we aren’t cycling is much closer to home. It is not just lack of infrastructure, or lack of fitness, the reason that 66 per cent of Brits cycle less than once a year, is because of status.

An obsession with social status is hard-wired into our brains. As we have built a society that relies on cars, the bicycle has slipped to the periphery, and gone from being regarded as a sensible mode of transport, to a deviant fringe-dwellers choice.

Even though cycling to work has been shown to be one of the most effective things an individual can do to improve health and longevity, researcher David Horton thinks that there are a set of collective anxieties that are stopping us getting in the saddle. These include not just an unwillingness to be made vulnerable, but fear of being thought of as poor.

A quick look over the North Sea shows that there is an alternative. Danish culture has elevated cycling to the point of reverence, and the social status of cyclists has followed. As we have busied ourselves building infrastructure that testifies to the dominance of the car, Denmark has been creating magnificent architectural features, aimed specifically at bike users. The Cycle Snake, or Cykelslangen, literally suspends the cyclist above the city, metaphorically elevating the cyclist and creating a sense of ceremony.

In doing so, they are subtly persuading people of all backgrounds to see past their prejudices or fears and take it up as the clearly better choice. This means there are more women cycling, more older people cycling, and more ethnic minorities cycling. The activity is less dominated by comfortably middle class white males: there are cyclists from every side of the community.  

The Cykelslangen, under construction in 2014. Image: Ursula Bach and Dissing+Weitling architecture.

Despite abstract motivations like getting ripped and conquering global warming, it is only when the bike path becomes the obviously better choice that people will start to cycle. It can take years of traffic jams before people try an alternative, but if you make motorists jealous of cyclists, then the tables can quickly turn.

Another way that Copenhagen has done this is by taking privileges normally afforded only to the motorcar, and given them to the bike. The city has ensured that cycle routes do not include blind corners or dark tunnels, and that they form a complete, coherent network, and a steadily flowing system – one that allows cyclists to maintain a reasonable pace, and minimises the amount of times you have to put your foot down.

The ‘Green Wave’, for example, is a co-ordinated traffic light system on some of the main thoroughfares of the capital that helps minimise the amount of cycle congestion during peak times. It maintains a steady flow of cycle traffic, so that there is no need to stop at any point.

Small measures of prioritisation like this one increase the sense of safety and consideration that cyclists experience, making it natural for the citizens of a city to act in their own self-interest and get on their bike.

As well as redefining the streets around the bicycle, the Copenhagen Cycle Chic blog positively fetishises cyclists. The tagline “dress for your destination, not your journey” depicts the social fashion life of the cycle lane as a “never ending flow of happy people heading from A to B”. Its writers are  literally making cycling sexy, dispelling the idea that going anywhere by bike is odd, and helping the world to see that the bicycle is actually the ultimate fashion accessory.

So unlike in London, where cycling is still a predominantly male pursuit, Copenhagen sees a more even split between men and women. Not just because they feel safer on the roads, but because culturally they are comfortable with their appearance as part of a highly visible group.

So while our low level of cycling is partly due to our physical infrastructure, it is also due to our cultural attitudes. The mental roadblocks people have towards cycling can be overcome by infrastructure that is not only safe, but also brings old-fashioned notions of dignity and grace into the daily commute.

Of course, office shower facilities might stop cyclists being ostracised, too.