Think ahead if you plan to travel West O Street on Monday. The Harris Overpass, the concrete bridge that carries O Street traffic over the railyards and Haymarket District, is set to close at 9 a.m. Monday.

The 1954 bridge will be cut apart and dismantled in a reconstruction project that will close the major arterial street for one year.

More than 26,000 cars a day  cross it, but come Monday, drivers will need a detour, and it’s best to choose in advance.

Two official detours were carefully selected for safety and efficiency, said Kris Humphrey, project manager for the city’s Public Works department.

The roads were upgraded to handle extra traffic, and they don’t cross busy train tracks, cut through neighborhoods or push traffic onto narrow roads.

While other options to get from downtown to West O Street are available, Humphrey strongly advised people to use these.

* North from downtown: Interstate 180 north to Cornhusker Highway, west on Cornhusker to First Street, south on First Street, which curves into Charleston Street, to Sun Valley Boulevard, south on Sun Valley to West O Street.

* South from downtown: Rosa Parks Way (formerly known as L Street turning into Capitol Parkway on its way west) west to U.S. 77, then north to West O Street.

* Pedestrian detour from downtown: Take the pedestrian bridge on North Eighth Street toward Haymarket Park, go west of the park and take the Salt Creek Trail, which follows Salt Creek.

* Bus routes: StarTran’s weekday and Saturday routes for No. 12-Arnold Heights line will be adjusted during construction, and an additional bus has been added. Detour route schedules are available on the buses and at the StarTran office, 710 J St.; at various local agencies; and at lincoln.ne.gov (keyword: StarTran).

West O Street will remain open to businesses between Sun Valley Boulevard and Second Street.

City planners estimate driving the detour routes will take 5 to 7 minutes longer than using West O Street.

The overpass’ safety rating qualifies it for federal bridge replacement money, providing 80 percent of the $18 million replacement.

Demolition will take two months, said Bruce Sweney, construction engineer for the city.

Work will begin on the east side, and rebuilding will follow the demolition. That way, work should finish in the Haymarket by mid-June, allowing the parking area beneath the bridge to open in time for summer events like the Farmers Market.

Over the next weeks, covered pedestrian walkways will be built so people can access businesses beneath the bridge.

The new bridge design leaves room beneath for future Haymarket District development. It will feature fewer supports — 14 rather than 28 piers — due to advances in bridge technology, allowing space where new roads could be built.

The new bridge’s alignment will be almost identical to the old. Features such as on-ramps and entry points will stay the same.

The life span of the new overpass is estimated to be 100 years.

A bridge has crossed the rail yard since the late 1880s. The Harris Overpass is the third bridge at the site and was named for John F. Harris in honor of the Harris family, which donated the land for Pioneers Park.