The exit could relieve some congestion inside the new Highway 99 tunnel. But it may also attract new trips that would otherwise use First or Fourth avenues south.

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Highway 99’s new First Avenue South/downtown offramp opened very early on Tuesday, in time for the morning commute, according to the Washington State Department of Transportation. The opening occurred about two weeks after traffic started running in the new tunnel from the stadiums to South Lake Union and other interchanges.

The northbound exit leads to the sports stadiums, waterfront Alaskan Way, and the Edgar Martinez Drive overpass onto Interstate 5 and Interstate 90. The offramp includes a bus lane, and King County Metro Transit says it will use it immediately Tuesday morning to replace this winter’s detour that included Fourth Avenue South.

This video by the Washington State Department of Transportation shows the exit and some driver options — which can be convoluted or even require backtracking.

The overpass is the first in the world to use a new earthquake-resistant design that flexes more than a standard bridge, by including fiber-reinforced concrete and titanium-alloy rebar.

The stadium-area exit could relieve some congestion inside the tunnel, by letting drivers enter downtown from the south, rather than travel underground until the north-side Mercer Street exit.  But it may also attract new trips that would otherwise use First or Fourth avenues south.

Demolition began Friday on the now-closed Alaskan Way Viaduct, which drivers used since 1953.