A tunnel, not a replacement bridge, is in the future for a Washington Street rail overpass at Clark Street, Vicksburg officials decided Thursday.

The design was among four being considered. It is more expensive than a replacement bridge, but is expected to last longer and be less burdensome to traffic during construction.

The plan calls for a steel arch to be built over the rail tracks, fill dirt to be added and a roadway built at the current bridge level.

The plan addresses erosion and slope slippage that have plagued the deep trench for years. Several shoring-up projects have been undertaken, but the bridge, near DiamondJacks, is now closed to heavy vehicles.

Mayor Laurence Leyens called the tunnel &#8220a permanent solution.” It was chosen during an informal meeting among city personnel, Kansas City Southern Railroad and engineers Thursday at City Hall.

Based on initial estimates, the tunnel design chosen would cost $1.7 million more than the least-expensive alternative, but the consensus was that the extra investment would pay off in the long run.

Among those helping plan the project are personnel of the Jackson office of the Neel-Schaffer engineering firm. Leyens asked that an accelerated schedule for the project be developed.

The city voted in April 2004 to spend $16,000 to determine how and when to replace the overpass, then about 60 years old.

The project is to be paid for using proceeds from a $16.9 million bond issue the city approved in October.

The city is to be reimbursed for part of the project’s cost with $4.75 million in federal transportation funds the city secured in 2005. The money is to be paid in four payments, one during each of four fiscal years starting Oct. 1. Costs in excess of the $4.75 million will be paid by local taxpayers.

Counts show average daily traffic of 10,000 to 16,000 vehicles in the area.

The train tracks below are used by about 24 trains a day, said KCS director of engineering Lee Peek. The city will also investivate whether KCS can manage the entire project.

Another design idea also called for a tunnel, but with a more-gradual slope than on the accepted design. It was estimated to cost about $800,000 more than the one chosen. Leyens said KCS could opt for the more-expensive design if it would pay the difference.

Also discussed at Thursday’s meeting were plans for KCS and the city to collaborate on closing some railroad crossings in the area, including those where tracks run just east of Pearl Street at Speed and Klein streets. Such closures reduce the risk of accidents. In exchange for the reduction in risk of liability, the railroad is to contribute to the overpass deal money or work that the city would otherwise have to pay or do, Leyens said.

Another reason the city wants to reduce the number of crossings in the area is that trains sound their horns when traveling through crossings and the tracks there pass near historic homes and bed-and-breakfast inns. Among the city’s long-range goals are to create a &#8220quiet zone,” Leyens said.

Also long-range, the city would like to build a connecting road west of the railroad tracks between around Fairground Street and the Vicksburg Convention Center area. Among the benefits of such a road is that it would provide better emergency access to that area, Leyens said. KCS has agreed to donate former railbed that has been vacant since the most-recent track-realignment in that area, in 2004.

In late 2005, KCS and a railroad company whose network is to the east and north, Norfolk Southern, announced a joint venture to invest $300 million in track upgrades over four years. Train traffic is expected to increase to 40 or more trains following that work.