Drivers in downtown Dallas should prepare for detours along Central Expressway frontage roads beginning today.

For the next two weeks, work on the DART Green Line will require detours near Good-Latimer Expressway and Live Oak Street, state transportation officials said.

Traffic on the main lanes of Central Expressway will not be affected, officials at Dallas Area Rapid Transit and TxDOT said Thursday.

Mark Ball, a spokesman for DART, which requested the detours, said most drivers won't notice the changes.

"I don't think there will be an impact at all," Mr. Ball said.

Still, drivers on the street-level frontage roads near downtown will be rerouted.

Here's how it will affect motorists:

•For drivers headed south, toward downtown, the change will become noticeable as they approach Routh Street. Southbound drivers on the frontage road will be required to veer left at Routh and travel east to Live Oak Street along Good-Latimer Expressway.

•Drivers leaving downtown who turn left off Live Oak Street to reach the northbound frontage road will face changes, too. They will continue for about two additional blocks to Good-Latimer Expressway. A left turn onto Latimer will take drivers to the northbound frontage road for Central Expressway.

•In addition, drivers southbound on the Central Expressway frontage road will not be able to access Interstate 45.

The detours will last until Aug. 8, said David Lott, who is the TxDOT engineer in charge of the Central Dallas area. They were requested by DART, whose work crews are building the new Green Line rail project.

Construction for the new rail line caused significant traffic delays last summer, when TxDOT approved a request by DART to close the Live Oak Street exit off southbound Central Expressway. That exit is expected to remain closed until next year.

After three months of complaints, and traffic jams occasionally stretching past Uptown, TxDOT restriped the pavement near the exit, restoring one of the lanes that had been closed. Traffic soon eased.

Mr. Ball said it's unlikely the changes that begin today will have a similarly bad effect on traffic. He said the detours were approved in advance by TxDOT and the city of Dallas.

TxDOT's top engineer in the region, Bill Hale, said the agency expects little effect from the changes but conceded the agency should have given drivers more time to prepare for them.

The changes take effect before 5 this morning.

The new rail line will stretch from Carrollton south through Deep Ellum, past Fair Park and ending at a Buckner Station in Pleasant Grove. Service for the first stations will begin next fall, in time for the State Fair of Texas.