Bridges = No Salt Zones.....Is this an NYC only thing ?

[nookandcrannycar]

I just returned from NJ/NYC. While I was there, I walked across the Brooklyn Bridge, and then back to Manhattan. I saw a 'No Salt Zone Begins' sign at the entrance to the Manhattan side of the bridge. I just did an internet search re this and one post suggested that this is done to reduce water pollution. This same post indicated that the other bridges in NYC follow the same practice. I've driven across the Bronx-Whitestone Bridge and the GW Bridge (not during Winter)...and I don't remember seeing that sign. Here in my little corner of Texas, the very few times I've seen salt on the roads...it was ONLY on bridges.