I decided to publish this article this week as a way to share my thought on the road widening project on highway 20 in Lévis and the Pierre-Laporte bridge connecting it to Quebec City. Many think that those road widening projects are going to solve congestion in the national capital, but using the induced demand principle as well as some other arguments, I’ll try to tell you why I don’t think it will solve congestion.
What is induced demand? Induced demand is a well-known principle in urbanism which can come down to a sentence: “Build and they will come” which basically means that if they build a new lane on Tuesday, it won’t me Monday’s traffic sharing this lane, it’ll be newly created Tuesday traffic which exceeds what Monday was which in the end, will slow it down even further.
Opening a new lane gives people that used to take the bus or carpool, that there will be space for them in their individual cars on this new lane, so they will use it instead of taking the bus. Everyone know a bus is more space efficient than a car, so let’s say that there’s 50 people on a bus, and 10 of them take the car instead thinking “That new lane is going to be empty” what will happen is that that new lane will have to accommodate the bus and 10 more cars.
Atop people who will leave the bus for the car, are the people who left early to “beat traffic”. It’s that one person that used to leave at 6 and now will leave at 7:30 because of that new lane. If 1000 people leaving from 6 to 7 all start leaving at 7:30, even though there’s a new lane, it won’t be able to handle it because 1000 cars is still 1000 cars no matter how many lanes you have.
Highway 401, in west Toronto
Now let’s talk about something else than induced demand. More lanes = more cars on the far-left lane = more lane changes to get to exits. In North America, we estimate that 1 out of every 10 car crashes is due to a wrongly done lane change. On highway 401 (Picture), that is 3 crashes a day due to wrong lane changes.
A crash while changing lanes will usually close 2 lanes, the one you’re departing from and the one you’re getting into. Those lane closures will significantly reduce the flow of the road. On a 3-lane highway, a crash closing 2 means only 1 lane stays open to accommodate traffic from 3 lanes
My last argument is the congestion at the end point of the trip. Let’s say you’re leaving Lévis and going into Old Quebec city. We could widen the 20, the 440 and a reversible lane on the Pierre Laporte bridge, but how do we manage all that when it enters the Old city? We can’t widen roads there because it is all built up, so what will often happen, is congestion on the 440 will become higher because the entrance to old Quebec is not meant for that number of cars. What was 2 lanes into 1 is now 3 into 1 which just makes it a bigger chokepoint. People will then try and use alternative routes which aren’t as optimised and that will then make what is described as gridlock!
Green: Adapted route Orange: Non-adapted route people will take Dark: Congestion
A solution is not a third link that is a highway that will create congestion on the east side of Quebec, it is a viable alternative to driving, such as: Bus only lanes, a tramway, or a third link axed towards transit that will be reserved to busses, tramways or bikes.
Tramway and pedestrian tunnel in Lyon, France (My proposition for the third link!)