The Lititz Pike bridge is expected to open to traffic Wednesday, inaugurating new traffic patterns around one of Lancaster City’s main north-south gateways.

Southbound traffic is slated to begin moving onto the new bridge sometime this morning.

Northbound traffic is slated to be changed over by early afternoon, after workers change the traffic lines, move concrete barriers and adjust the traffic signal at Keller and Marshall avenues.

Traffic will continue to be limited to one lane in each direction. The limitations will allow the closure of the intersection with Marshall Avenue and the removal of the old bridge.

The traffic pattern on McGovern Avenue is also being changed. The street will become two-way between North Duke and North Queen streets. The change will allow better access to the Lancaster Amtrak station.

Access to Marshall Avenue will also be blocked from Lititz Pike.

PennDOT will be posting detours for both southbound and northbound traffic to reach Marshall Avenue businesses. Because detour roads have to accommodate all permitted vehicles — even tractor trailers — the route must stick to major roads.

As a result, the detours each pass the blocked Marshall Avenue intersection and then go far out of the way to bring drivers back from the east side.

The northbound detour is 4.5 miles long. It takes drivers onto Oregon Pike, Route 30, New Holland, Fountain and Martha avenues before reaching Marshall.

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The southbound detour is 3.5 miles. It takes drivers onto Duke, Chestnut and Plum streets, New Holland, Fountain and Martha avenues to get to Marshall.

With the bridge opening, traffic will use the new alignment that connects Lititz Pike directly with North Duke Street.

Previously, southbound traffic took a one-block dogleg onto McGovern Avenue before turning onto Duke. For the past year, while the new bridge has been under construction, the dogleg has been on Liberty Street.

The $26.26 million project is expected to be completed in late October after demolition of the old bridge, which has carried motorists over the railroad tracks since 1939.

When complete, the bridge will be two lanes in both directions.

Wednesday’s opening of the new bridge could be delayed by heavy rain, said Fritzi Schreffler, a spokeswoman for PennDOT District 8.

AccuWeather anticipates cloudy skies giving way to some sunshine this morning.

In the event of a morning delay, the new bridge would be opened later Wednesday afternoon or Thursday, Schreffler said.