Quote:
Originally Posted by JManc
Infrastructure like highways rarely last 50 years. 30 years is about when things start breaking down and needing to be rebuilt. Why would the state invest and over engineer something that will never last its intended lifespan.
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I would offer 2 examples from Toronto.
The first is the Price Edward Viaduct/Bloor Viaduct.
This large bridge connects Bloor Street (downtown Toronto) to Danforth Avenue on the other side of the Don Valley.
It was opened in 1918.
Its not merely that its still standing.....
Its that when built, provision was made for a lower deck which could carry either streetcars or subways.
Important to note here, is Toronto had no subways in 1918, nor would it gain any at all until 1954.
Further, that route wasn't a serious contender for the 1st, or even a second line when this bridge was being built.
Danforth Avenue was a dirt road at the outer limits of Toronto's urban reach.
Yet, in 1966, subways started trundling under this bridge.
That's future-proofing that worked. The bridge still stands today, and the subway operates 53 years on as well.
https://en.wikipedia.org/wiki/Prince_Edward_Viaduct
The planner behind this bridge also built a water-treatment (drinking water) plant in Toronto's east end.
It too still operates. It was built to serve a population of 800,000. A number several times larger than the City at the time.
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As to highways, Toronto's growth and induced demand mean that 60 years of surplus capacity hasn't been achieved on any major highway of which I can think.
However, the rights-of-way were acquired with future expansion in mind which is why the 401 has moved from being 4 lanes (2 in each direction) to 16-18 lanes without purchasing any new land.
In terms of general lifespan, in Toronto, the road reconstruction manual aims for reconstructing a road every 60-70 years, not every 30.
Resurfacing is typically every 20-30 depending on volume of use.