The Road-Building Paradox
As work proceeds on the Gateway project – $3.3 billion worth – and as we put on hold any investment in transit, here’s an intriguing phenomenon to note (from Stephen Ingrouille’s Transport Newsletter):
The Pigou-Knight-Downs paradox is the observation that people will tend to balance car trips with rail trips until the two are at equilibrium in time and comfort. Building more roads attracts commuters away from rail, which reduces or diverts investment and increases the travel time, forming a vicious cycle.
This means that building more roads and not investing in faster rail transport results in a general overall decline in traffic speed. This is nowhere more clear than here in California where, despite enthusiastic freeway building, a bike is a competitive mode.
The solution is simple and necessary: invest real amounts in improving rail transport, in particular improving the grade-separated heavy rail network and linking the feeder tram network to stations.”
Ref: Nathan Hurst, The Age, 5/9/09
More below on the Pigou-Knight-Downs Paradox.
“Downs-Thomson paradox, also referred to as the Pigou-Knight-Downs paradox, states that the equilibrium speed of car traffic on the road network is determined by the average door-to-door speed of equivalent journeys by (rail-based or otherwise segregated) public transport. It follows that increasing road capacity can actually make overall congestion on the road worse. Ref: Wikipediahttp://en.wikipedia.org/wiki/Downs-Thomson_paradox
This occurs when the shift from public transport causes a disinvestment in the mode such that the operator either reduces frequency of service or raises fares to cover costs. This shifts additional passengers into cars. Ultimately the system may be eliminated and congestion on the original (expanded) road is worse than before.
The general conclusion, if the paradox applies, is that expanding a road system as a remedy to congestion is not only ineffective, but often counterproductive. This is also known as Lewis-Mogridge Position and was extensively documented by Martin Mogridge with the case-study of London on his book Travel in towns: jam yesterday, jam today and jam tomorrow?
An article of 1968 from Dietrich Braess now at the Faculty of Mathematics in Ruhr University, already pointed out the existence this counter-intuitive occurrence on networks – the Braess’ paradox states that adding extra capacity to a network, when the moving entities selfishly choose their route, can in some cases reduce overall performance.”
Beautifully simple.
I guess BC politicians either don’t think theories such as this don’t apply to Vancouver, or they aren’t really interested in reducing congestion.
Typo apologies – please ignore second “don’t” in my first comment.
Or maybe the politicians are only listening to (and taking money from) the BC Association of New Car Dealers and Keiwit-Flatiron, who in turn run businesses on the premise that these theories are untrue.
I’m not that it’s true that they (New Car Dealers and Keiwit-Flatiron) run businesses on the premise that theories like this are untrue. They just don’t care they’re true or not. All they’re interested in making some money by selling cars and winning construction contracts. Once the highways are finished, the bridges are open and the cars are sold, congestion is someone elses problem. Future governments can deal with it.
Sorry typo again – “I’m not *sure that it’s true that they ….. “
Yes, that’s true Chris. I guess in my book, not caring is pretty much equal to not believing, as the outcome is quite similar!
Unfortunately once that thinking gets into government, it becomes institutionalized and is very hard to overcome. I am currently dealing with the Province for transit in my job (local government) and their mantra is roads. Sadly enough, most people at my work (including supposedly enlightened planners) still refer to the Ministry of Transportation and Infrastructure as “Highways.”
Steve – sounds like many gov. departments at various level suffer from some serious groupthink.
No serious evaluation of proposal alternatives and anyone who doesn’t support the group consensus is seen as a threat or otherwise incompetent.
There’s a problem with this little theorem, in that it makes no mention of prices or costs. People will select the mode with the lowest overall cost, which is a combination of prices paid and time, which has an implicit dollar value, spent in travel. People may well select the longer journey if it’s other costs are low enough that the extra time is worth it.
For example, I live in Maple Ridge, and a few weeks ago I had to make a trip to a shop in north Surrey, and 104th and 152nd. On the trip south I took the new Golden Ears Bridge and 96th Ave, paying a $3.30 toll for the privilege. On the trip back home, I went Port Mann-Mary Hill-Pitt River Bridge and Lougheed, with no tolls.
The trip south took 19 minutes, the return trip 22 minutes. It’s worth it to me to pay the toll if I value my time at over $60 per hour. Which I don’t. So no more Golden Ears trips unless we’re heading to the Ferry, for which destination the time savings are worth $3.30.
Ah, but time is money, is it not? You just provided the equation. Certainly we can’t expect everyone’s time value to be the same, but it may not that wide a spectrum.
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