WASHINGTON — Extreme weather is a growing threat to the nation’s lifelines - its roads, bridges, railways, airports and transit systems. That’s leaving states and cities trying to come to terms with a new normal.

Superstorm Sandy is the latest and most severe example. It inflicted the worst damage to the New York subway system in its 108-year history. New York isn’t alone; intense rain, historic floods and record temperatures are taking a toll on transportation across the country.

Transportation engineers build highways and bridges to last 50 or even 100 years. Now they are reconsidering how they do that.

The American Association of State Highway and Transportation Officials is weighing rewriting its standards on design, construction and maintenance of roads and bridges to reflect new weather extremes.