A few days ago I wrote a post talking about what happens when you demolish an urban highway. It was a link to an article giving 5 examples of cities that have removed their urban highways and benefited.

After I wrote the post, a number of people responded on Twitter. Some thought it was a great idea and gave examples of other cities, such as Detroit, that are thinking about doing the same. But others responded and said that I was out of line. And that while it might work in some cities, it simply isn't a viable option in cities like Toronto.

So as somebody who believes we should be taking down the Gardiner Expressway, I thought it would be worthwhile to revisit the topic and provide a bit more information.

To be clear, I'm not suggesting we remove the Gardiner and replace it with nothing. My belief is that we should replace it with a broad surface street that would still move lots of cars, but that would make our waterfront much more open and accessible to everyone.

So how is this feasible?

Again it comes back to the concept of induced demand. Back in 2009, two economists from the University of Toronto and University of Pennsylvania — which are actually both of my alma maters — published a study called The Fundamental Law of Road Congestion.

In it they discovered something really fascinating: there's a near perfect relationship between new roads and highways built and the total number of miles driven. In other words, as cities increased road capacities (during their study period of 1980 to 2000), the amount of driving went up just as much.

What this should tell you is that trying to build your way of out road congestion is usually a losing proposition. That's why every large city has a traffic problem. Try and think of one that has solved this. And as much as it might seem intuitive to tell people at cocktail parties that your city simply needs to build more roads and highways, it's typically not that simple. (In my view, the solution is road pricing.)

The other really interesting thing that this study revealed is that it works both ways. When you reduce road capacity, drivers start to disappear. People choose to live closer to where they work. People choose transit. People go into the office at different times. People make all sorts of different decisions in response to this road change, just as they do when there are more free roads available to them.

So within a reasonable band (obviously you can't remove all roads), there is no perfect amount of road capacity. If you added another lane to your highway, it would be full. If you took away a lane, it would end up equally full. That's why removing the Gardiner Expressway isn't lunacy.

Instead, it actually makes a lot of sense:

• It's the cheapest solution (compared to repairing it or burying it)
• It would free up money for transit and other mobility solutions
• It would make our waterfront more open and accessible
• It would beautify our downtown
• It would increase land values all along the waterfront

And since we're still in the early days of developing our eastern waterfront, now is the time to do it. The longer we wait, the harder it'll get and the more expensive it'll get.

So I hope that the leaders in this city will think long and hard about this as opposed to immediately assuming we need an elevated highway to keep this city moving. The last time I checked, it doesn't work so well in its current state.

Images: Before and After the Embarcadero Freeway in San Francisco (via Gizmodo)