Days before the next stretch of Raleigh's Outer Loop is due to open for traffic, the state Department of Transportation is scrambling to give it a new name.

Workers this week began replacing red-and-blue Interstate 540 shields with black-and-white diamond signs to mark the new 4.5-mile stretch of six-lane freeway as N.C. 540.

"It's going to look like an interstate, and it's going to drive like an interstate, but it's just going to be called N.C. 540," said Kevin Lacy, state traffic engineer.

The new part will extend the 29-mile Outer Loop from Interstate 40 through Research Triangle Park to N.C. 55. DOT engineer Phillip Johnson, who is overseeing the $102 million project, said he hopes it will open to traffic late next week.

The 540 identity crisis stems from a state Turnpike Authority plan to build the 18-mile Triangle Expressway through RTP and western Wake County. The toll road would overlap with part of the new 540.

No tolls will be collected when commuters start using the new stretch of 540. But if the Triangle Expressway opens as scheduled in 2011, drivers eventually will pay tolls to use the N.C. 540 stretch between N.C. 54 and N.C. 55.

After gaining federal approval in January for the future switch to a toll road, turnpike officials lobbied the DOT not to label the new stretch of 540 an interstate. Transportation Secretary Lyndo Tippett, who doubles as turnpike board chairman, settled on the N.C. 540 name in May.

"The final decision was to maintain the 540 designation for continuity ... so drivers would not all of a sudden lose the road they were driving on completely," Lacy said, adding that "we are also, believe it or not, trying to minimize the confusion. We didn't want I-540 to end at some point for no reason."