Traffic as Hot Air

Lately I find myself reading a lot of articles about traffic. I never used to care about traffic; as a pedestrian I really worried only about the cars in the street I was about to cross.

But the fight against the Wellington Street Extension has forced me to think bigger picture. And like a lot of people, I’ve been reading the recent articles and editorials in Toronto newspapers concerning the Gardiner expressway. Much of what I read reassures me that our efforts to stop the WSE, if successful, will not result in the north-south gridlock that some people fear.

In Saturday’s Globe and Mail, Oliver Moore wrote the following about Toronto’s dilemma:

Modern research into traffic has shown that cities can’t build their way out of congestion. Much of the future growth will have to be served by transit.

Meanwhile, urban downtowns are again being populated with residents. Some businesses are relocating back into the centre of cities. And the younger generation is showing much less interest in driving – or even getting a licence – than those who came before.

All of this means urban highways will have to justify their worth in a way they didn’t before. What’s good for drivers won’t necessarily be seen as being good for the city.

Moore, who lives in New York, tells the story of Sam Schwartz, an assistant engineer and the director of research and traffic studies for New York City’s traffic department in the 1970s. It was his job to figure out the impact on drivers caused by the collapse of part of the West Side Elevated Highway in Manhattan — an event expected to produce a major traffic crisis. What happened was surprising:

A lot of the traffic just disappeared.

There was an uptick of traffic on the avenues toward the west of Manhattan. Transit also absorbed some, though this area is not well served by the subway and the 1970s-era system was decrepit and crime-ridden. But these increases couldn’t account for all the lost capacity. Tens of thousands of car trips evaporated.

The counterintuitive finding is most easily understood by thinking of traffic as a gas instead of a liquid. Research shows that traffic will expand to fill new space, a phenomenon dubbed induced demand. It will also shrink if the available space does, a pattern known as vanishing traffic.

Where does it go? People modify their behaviour. Some will switch to transit or other modes of travel, others will tweak when they drive. And discretionary trips, a surprisingly large portion of rush hour traffic, may be rethought.

Last week I also enjoyed this excerpt from Jeff Speck’s book Walkable City:

Traffic studies are bullshit. They are bullshit for three main reasons:

First: The computer model is only as good as its inputs, and there’s nothing easier than tweaking the inputs to get the outcome you want.

Second: Traffic studies are typically performed by firms that do traffic engineering. This makes perfect sense—who else would do them? But guess who gets the big contract for the roadway expansion that the study deems necessary? As long as engineers are in charge of traffic studies, they will predict the need for engineering.

Finally, and most essentially: The main problem with traffic studies is that they almost never consider the phenomenon of induced demand. Induced demand is the name for what happens when increasing the supply of roadways lowers the time cost of driving, causing more people to drive, and obliterating any reductions in congestion…

The most comprehensive effort remains the one completed in 1998 by the Surface Transportation Policy Project, which looked at fully 70 different metropolitan areas over 15 years. This study, which based its findings on data from the annual reports of the conservative Texas Transportation Institute, concluded as follows:

Metro areas that invested heavily in road capacity expansion fared no better in easing congestion than metro areas that did not. Trends in congestion show that areas that exhibited greater growth in lane capacity spent roughly $22 billion more on road construction than those that didn’t, yet ended up with slightly higher congestion costs per person, wasted fuel, and travel delay.

I love reading this stuff — and it’s sounding a bit familiar, isn’t it? We know this! I’ve heard a number of these arguments — roads attract traffic, young people aren’t as interested in driving as they used to be, congestion changes behaviour, investment in transit makes sense — from people (members of the public and council) speaking against the WSE in council chambers. Kingston has a habit of thinking of itself as unique. But maybe it should look to other cities and save itself some grief — and money.

— Anne Lougheed


One thought on “Traffic as Hot Air

  1. That young people aren’t interested in driving appears to not be accurate, as there has been a massive rebound in car sales (10 year high) including to the young

    “First, millennials, now the largest demographic block in the U.S., are not abandoning car ownership. Those born after 1980 accounted for 27% of new vehicle purchases in the U.S. last year, up from just 18% in 2010, according to J.D. Power and Associates.”

    I think its important not to promote inaccuracies to get the public onboard. Over the top inaccuracte statements did not help sentiment toward some campaigning for KCVI


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