Bridges are expensive : bridge failures are more expensive.

The failure of the new york state thruway bridge over schoharie creek demonstrated once again that bridge failures are more expensive than just the bridge itself, and that it would be prudent to assess the vulnerability to floods of all existing bridges over alluvial rivers. All such bridges are vulnerable to some degree unless they have been built by design or by engineering judgement for the maximum flood to be expected and the worst geometry and flow conditions that may come into being during the life of the bridge - and with proper evaluation of all factors. The remedial measures needed to make an existing vulnerable bridge virtually invulnerable will probably cost more than comparable measures would have cost at the time it was built; but, nevertheless, the cost can probably be justified when life and limb and a year or two of traffic delay are considered. That nothing has ever happened to a bridge that is 25 or 50 years old may be just a matter of luck, and it is not a sufficient reason to not assess the vulnerability of the bridge. Luck can run out, and the failure of an old bridge can still be very costly.