Why do some Interstates, such as I-180 in WY, have traffic lights or at-grade intersections?
Usually Interstates are not allowed to have any cross traffic. In fact at-grade intersections have kept the new I-86 in New York from extending further east. But in these cases, AASHTO granted variances because there was no other reasonable way to build them. Wyoming I-180 is the only Interstate with no freeway portions. There are three stoplights. Why was it commissioned in the first place? The state of Wyoming wanted an Interstate serving downtown Cheyenne. It was to be freeway, but that idea was rejected. More information is at http://www.rockymountainroads.com/wyoming/i-180.html I-676 in Philadelphia, PA has some traffic lights between the Vine St Expressway and the Ben Franklin Bridge. Construction of a freeway connection would impact several historic landmarks. There is some doubt among roadgeeks as to whether I-676 actually goes this way; the official PennDOT maps label the freeway connection to I-95 as 0676 and put US 30 on the Ben Franklin Bridge. There is an I-676 shield on t
