South Carolina’s unfunded highway and bridge needs are estimated at $29 billion, which translates into a $1.5 billion allocation annually over the next 20 years. So how is transportation doing this legislative session? Not so good.

So far, two House proposals appear to have a chance of advancing this session. One is a plan by House Speaker Bobby Harrell to shift the taxes from the sale of motor vehicles to the Department of Transportation. It would bring an estimated $80 million to the DOT next year.The House also has backed a $60 million allocation for bridge work.

That translates to less than 10 percent of what is needed. It’s a start, but hardly enough.

The best bet in the state Senate is a flawed plan for a $50 million allocation. It would leverage $500 million in bonds for road projects — but not by the DOT.

Rather, the money would be controlled by the State Infrastructure Bank, which doesn’t have to meet the same standards of accountability required of the DOT under the 2007 reform of the agency.

The Infrastructure Bank was created to build projects too expensive for the DOT to undertake, and it did so with the construction of its first project, the Arthur Ravenel Jr. Bridge over the Cooper River.

There has been nothing of similar scope since then. Locally, serious questions have been raised about the SIB’s priorities, in view of its unrelenting support of the controversial I-526 project.

Better proposals for transportation funding already have faltered.

For example, Larry Grooms, chairman of the Senate Transportation Committee, recommended that 10 percent of new revenue be provided to the DOT on a recurring basis. His plan, which would have generated $70 million next year, was barely defeated in the Senate during recent budget deliberations.

Two House proposals to increase the gas tax failed to get out of committee. Each had the merit of taxing those who use the highways. Each recognized that the gas tax is a user fee. And the gas tax also is paid by out-of-state motorists, generating about 30 percent of its revenue.

Meanwhile, a House panel supported using Internet sales taxes for road building. That would be predicated on its approval by Congress.

The U.S. Senate has endorsed the idea, but the U.S. House hasn’t. If approved, there is bound to be competition for the $500 million or so it would generate in this state annually.

And a bipartisan S.C. Senate proposal to increase gas taxes and fees for a $1.3 billion bond issue has yet to advance.

But the $50 million SIB allocation was included in the Senate budget, and is expected to be considered as a separate bill today to ensure the money can be used to support the larger bond issue.

Expanding the authority of the SIB is a step backwards in accountability. Whatever the DOT’s shortcomings, the agency was improved by the 2007 reform.

In contrast, the SIB has operated as a second DOT without that agency’s constraints. The Legislature would do better to concentrate the state’s transportation resources within the DOT, which is still the lead agency for road construction in South Carolina.

Or ought to be.