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Originally Posted by Spocket
I think he was trying to point out that a lot of people here have sort of forgotten that simply building the highway doesn't generate vehicular traffic all by itself. I mean, if the cars have nowhere new to go or come from then there's no need for the highway in the first place, right ?
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That's just the thing though, highways do generate traffic all by themselves. With more road capacity people drive farther and more often than they would have if the road weren't there. On top of that, highways drive demand for new car dependent development and accelerate sprawl.
It works the same way with any mode of transportation. Better GO service generates more riders and so do new subway lines. GO Transit is expecting a 50% increase in off-peak ridership since they started running trains every half hour on the Lakeshore line. Induced traffic is a key part of the business plan for high speed rail, and that's demand that doesn't currently exist.
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Originally Posted by sonysnob
First of all, you could build your way out of congestion. It is impractical to do so in a city as large as Toronto, but a city has a theoretic cap of travel demand. Demand induction is as a result of latent demand. Travel demand has been suppressed due to congestion, and people take less discretionary trips. In a rural area, say Highway 69, the doubling of lane capacity as the highway gets twinned, would have no demand induction, as there was not a built up latent demand before the highway was twinned.
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Well if you can build your way out of congestion then it's never been done. Probably the most rigorous analysis of induced demand is the long term study done by the Texas Transportation Institute.
Its observations show just how hopeless constant highway widenings are in urban areas. A few highlights:
"These figures clearly indicate that there is no significant difference in congestion cost per capita between metro areas that invested heavily in highway construction and those that did not."
"The authors, UC Berkeley researchers Mark Hansen and Yuanlin Huang, found that at the metropolitan level, every 1% increase in new lane-miles generated a 0.9% increase in traffic in less than five years, which led them to conclude that "With so much induced demand, adding road capacity does little to reduce congestion.""
"Using a conservative estimate of $5 million per lane-mile, we estimate that over the 15 year period included in the TTI data, metro areas that invested heavily in road expansion projects spent $22 billion more than areas that built fewer new lane-miles, yet failed to produce lower congestion levels."
"In 1998, British researchers analyzed 60 road closures worldwide and found that on average, traffic decreased by 25 percent when a road was closed. In some cases, they found that an astonishing 60 percent of the driving trips disappeared."
Here's a more recent paper published in the Institute of Transportation Engineers Journal. Tellingly, there doesn't seem to be any research that comes to the opposite conclusion. As for Highway 69, obviously the induced demand of twinning that highway is a lot less than it would be in an urban area. The traffic volumes aren't very high and the level of service won't be a whole lot different than now, so there's not much theoretical advantage to driving the new highway. But the whole point of the project is to stimulate economic development in places like Sudbury, which doesn't happen without inducing some traffic.
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GO transit expansion across Toronto will provide some relief, but it is naive to think that that alone will relieve congestion either. Different transportation modes, including beloved trains (I can't believe the frequency in which HSR is brought up in the highway forum), have strengths and weaknesses. It is very effective to bring mass amounts of people from many points into a central down-town node on transit, however it is much less effective in point to point travel. Spending excessive money on transit evokes the law of diminished returns. It begins to cost more and more to serve trips that are poorly served by transit versus other modes.
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HSR comes up a lot in conversations like this because it's an effective alternative to highway expansion in densely populated areas like southern Ontario. Rail doesn't just serve point to point nodes. Any rail system, from GO Transit to the TGV in France, is served with huge park & rides at many stations. The GO corridors have the potential to allow people to get around the GTA reliably and quickly, all day, in all traffic conditions. No amount of road expansions have that potential. Lastly, I never claimed that transit could relieve road congestion. It can't. It can, however, provide a reliable alternative to sitting in traffic.