The collapse of part of a major tunnel's roof in Montreal is the latest example of the city's crumbling infrastructure. An overpass collapsed and killed five motorists in 2006 and another bridge was recently closed. (Hat tip Kate's Dirty Sister!)
Normally, I try and fail to be somewhat witty, but I think this, from the article, sums it up nicely:
It is also unclear whether the tunnel’s age played a factor in the accident. At nearly 40 years old, it is approaching what many engineers consider the expiry date for concrete structures.
Multiply that by the sheer amount and number of concrete structures around the city and you have the problem, in a nutshell.