High volume

Most heavily traveled sections of Interstate 526 (annual average of daily traffic):

West Montague Avenue to I-26

2012 86,000

2010 80,2002

2006 79,400

I-26 to Rivers Avenue

2012 79,700

2010 77,200

2006 75,300

North Rhett to Virginia Avenue

2012 78,400

2010 75,100

2006 74,400

S.C. Department of Transportation

Highway engineers say the widening of Interstate 526 to six lanes is a top priority, but officials holding the state's purse strings will have to agree in order for the project to get off the ground.

A key issue is traffic counts.

Along their most-traveled sections, both I-526 and Interstate 26 have seen increased congestion since 2006, but the problem has been worse on I-26.

The 2012 daily traffic count of 151,400 vehicles on I-26 from the U.S. 52 Connector to Ashley Phosphate Road is 25 percent higher than it was in 2006, according to DOT figures.

That translates to more frustrated commuters.

“It's a nightmare. Especially about 8 in the morning and about 6 p.m. You try to avoid those times,” said Rodney Busak of North Charleston.

Elizabeth Smith, also of North Charleston, agreed.

“I hate it. If it's in the afternoon around 4 or 5, it's terrible,” she said.

Danielle Ellington of Ladson said she got a reprieve from I-26 rush hour when she switched to a night job.

“It used to be horrible,” she said.

By the numbers, I-526 is less crowded than I-26. From 2006 to 2012, the busiest section of I-526, from West Montague Avenue to I-26, had an 8 percent increase in traffic to 86,000 vehicles daily.

But criteria other than traffic counts are used in the DOT ranking of interstates that need widening and other improvements, said Mark Lester, DOT's director of planning.

The projects are also evaluated on the ratio of traffic volume-to-capacity, truck traffic, safety and accident history, pavement condition, financial viability, environmental impacts and economic development, Lester said.

At stake in the DOT interstate ranking is how $500 million would be spent on improvements. That sum would pay for I-526 widening and a newly designed interchange with I-26, but the local project is No. 4 on the DOT statewide list of priority interstate work.

The DOT Commission has recommended to the State Infrastructure Bank board that it follow the DOT staff ranking of interstate projects when it comes to decisions about financing. If that happens, it is not clear how much money would be available for I-526 widening.

No. 1 on the DOT staff list is $240 million for a newly designed interchange connecting Interstate 85 and Interstate 385 in Greenville County. The remaining $260 million would be distributed along with other state and federal funds according to the prioritized list.

A joint meeting of the SIB board and DOT commission scheduled for Wednesday in Columbia aims to clarify how much money will be available for projects such as I-526 widening.

“That's the purpose of the workshop,” said SIB board Chairman Don Leonard of Myrtle Beach.

The bank board will not vote Wednesday on which projects to fund, Leonard said.

State Rep. Chip Limehouse of Charleston serves on the SIB board.

“If we did adopt their (DOT) prioritization that wouldn't be a bad thing. I don't know the mood of the board,” he said.

Limehouse said the Lowcountry has been well-served by the infrastructure bank, which has provided financing for projects such as the Arthur Ravenel Jr. Bridge and ACE Basin Parkway.

Legislators approved a $50 million appropriation for the DOT to send along to the SIB with its list of recommended interstate projects. The $50 million can be leveraged into $500 million, said DOT Commission Chairman John Edwards of Travelers Rest. He is also a member of the bank board.

“I hope that they (SIB) approve the list we sent them,” Edwards said.

I-526 widening is the only Lowcountry and coastal South Carolina project included on a list of 11 projects that the DOT identified as worthy of SIB consideration. The others are in the Upstate and Midlands.

The DOT commission's approval of the interstate improvement priority list comes less than a month after lawmakers OK'd a bill that used a combination of borrowing, new revenue from growth and reallocated sales taxes from vehicles to raise nearly $1 billion for the state's roads and bridges over the next 10 years.

In recent years, I-26 has been a beneficiary of road improvement funds. A $66-million project widened and resurfaced I-26 from six lanes to eight lanes between I-526 and Ashley Phosphate Road. Interchanges at Remount Road and Aviation Avenue were redesigned.

Two more I-26 improvement projects have been funded and are in the design stages, including adding lanes for nearly 30 miles eastward from Interstate 77, said DOT Commissioner Jim Rozier of Berkeley County.