The changes could take place after 9 a.m. Tuesday. If delays occur, the changes will be made Wednesday or Thursday. Drivers should pay attention to signs, pavement markings and electronic message boards designed to guide people through the area.

Drivers on the old highway must realize the old road will carry one lane of traffic in each direction. Northbound drivers especially will have to be alert because they will encounter southbound traffic in the left lane.

Here's what will happen Tuesday (or, if necessary, Wednesday or Thursday):

* Southbound traffic and northbound traffic will be reduced to one lane in each direction for about 1,000 feet at each end of the five-mile long project -- at Pinewood Drive on the south end and at Greene County Farm Road 6 on the north end. The speed limit in the merge areas will be marked 55mph.

This merge area is needed in order to move traffic away from where crews will build the permanent connections between the existing and new northbound lanes.

* Both new northbound lanes and both existing southbound lanes will be open to traffic along the 4-1/2 miles between the two merge points at Pinewood and at FR 6, with the speed limit set at 65mph.

* The old Missouri 13 northbound lanes between Pinewood and FR 6 will become a two-way road, with the speed limit set at 55mph.

* New stop signs will be placed at the northbound lanes for westbound traffic on Farm Road 44, Farm Road 34 and Highway CC and, eventually, FR 6. Only those four roads will connect the new lanes with the old roadway.

Construction of the five miles of new northbound lanes began in 2008. A 7.5-mile long section of new northbound lanes is also under construction in Polk County but it likely won't be done for another year.

Project Background

The new northbound lanes are right next to the straighter, more gradually-sloped southbound lanes built in the 1970s.

Northbound Missouri 13 follows the original hilly, curvy roadway built in the 1920s along five miles in northern Greene County and 7.5 miles in southern Polk County. Those remaining two sections of old highway -- 12.5 miles long in all -- are being replaced in separate projects.

A 60-foot wide grass median will separate the southbound lanes from the new northbound lanes along that 12.5 miles, making it consistent with the rest of Missouri 13 between Springfield and Clinton.

The project is designed to increase driving safety:
* Line of sight will be improved for drivers at side roads and driveways.
* Drivers will not have to negotiate sharp curves.
* It should reduce wrong-way driving -- especially going south in the northbound lanes.

The prime contractor for the Greene County project is Illinois Valley Paving, Springfield, Ill., for a low-bid amount of $7.7 million.

This project is made possible by federal funds earmarked by U.S. Sen. Kit Bond.