Say you get a deal on avocados. So instead of buying one or two avocados to put in a salad, you take six home assuming you will have ample for some other dish. You make the salad and then your friend makes guacamole some avocado sandwiches. Pretty soon, the avocados are all gone.
The idea here is that when there is an abundance of something, it will be consumed. This is the phenomenon of "induced demand." an economic phenomenon where more of a good is consumed after its supply increases.
This idea applies to road travel just as it does to avocados. In the case of roads, more or wider roads will fill up with more traffic as people realize that the new or widened road gets them to where they wish to go more quickly. Just like a discount on avocados, the new roads essentially lower the cost of driving by lessening the time and resources used up by a motorist stuck in traffic. Over time, travel time goes up again as the route becomes clogged with ever more drivers taking advantage of the new lanes.
Time and time again it has been shown that building more roads does nothing to relieve traffic congestion. Decades ago, this type of Induced demand was described by the British engineer, J.J Leeming in his 1969 book, Road Accidents: Prevent or Punish?
But perhaps the increase in congestion is caused by increased population? Randy Salzman, in his article in the Daily Progress, December 19, 2010 entitled "Build more highways, get more traffic," looked at the available research and came to some interesting conclusions. He found that since 1970, U.S. vehicle miles traveled have increased 121 percent — four times population growth. He also notes that, according to the Virginia transportation commission, "Congestion increases as people move outward from urban centers, and additional lane miles of roads to accommodate the people lead to more development, and more people, and more congestion, and more lane miles."
This is exactly what is happening in Ottawa right now. All over the city, from major highways to rural roads in ecologically sensitive areas, the doctrine of lane-widening continues without any basis in evidence. Sometimes, these new lanes are paired with new infrastructure for buses, bikes and pedestrians, but the fundamental, incorrect theory is still baked into the City of Ottawa's policy language: lanes are being built and widened to alleviate congestion, even though this argument isn't based on any evidence at all.
The result is a city with lopsided funding commitments that compete to crowd out key environmental investments. For example, in the 2018 budget, the City of Ottawa allocated a mere $500,000 for its climate plan and claimed that it was cash-strapped due to other spending commitments. Meanwhile, the City is pledging to spend hundreds of millions of dollars for priority road projects as part of its Transportation Master Plan.
The City states that it wants to decrease congestion and get people out of their cars and onto public transit, bikes or sidewalks. Experience tells us this is not going to be accomplished by building more roads. The only way to decrease congestion and get more people to walk, cycle or use transit is to make these forms of transportation more accessible. The City of Ottawa is now making record investments in light rail, but more work is required to tip the balance towards a more walkable, cyclable city by putting money currently earmarked for new roads into projects that actually work.