The Utah 2015 Transportation Alliance, led by the Salt Lake Chamber of Commerce, will continue to lobby reluctant senators right up to the deadline 48 hours in advance of the special session, likely to be held Sept. 19 or 20, Chamber spokeswoman Natalie Gochnour said Wednesday.

The alliance has been lobbying lawmakers all summer to support special session legislation that would allow counties to vote to raise sales taxes, rather than property taxes, to accelerate TRAX, commuter rail and road projects.

At caucus meetings Tuesday, lawmakers split on whether to take up such a measure during a planned one-day session.

During a closed-door caucus, House Republicans endorsed including the measure on the session agenda. Senate Republicans in their closed-door meeting chose not to support or reject the draft legislation.

"That vote came because the bill had too many unanswered answers," said Senate President John Valentine.

Many legislators wanted the bill to apply statewide, not just to Salt Lake County. "We are concerned about the ability to handle the infrastructure needs of the state, including roads and water, not just transit," Valentine said.

Whether a rewritten bill can be produced to satisfy senators remains to be seen, Valentine said. "If they come back with a bill as complex as the one yesterday, it is going to be extremely difficult to get support for it."

Gochnour said the Senate just needed more lobbying. "We have support in the governor's office," she said. "When senators have more information, they will be inclined to support the sales-tax option."

Even though the House members backed the proposal, they wanted to be able change it so it wouldn't lock the tax money into mass transit and transit corridor preservation.

"The House took a position but that they would like to see something a little more flexible," said Rep. Wayne Harper, House chairman of the Revenue and Taxation Interim Committee. "They wanted road projects included."

Gochnour said timing is crucial, because unless the Legislature endorses the measure during the special session, counties won't be able to put it on November's general election ballots.

Meanwhile, the Salt Lake County Council already has placed on the ballot a proposed property tax increase that would allow four TRAX lines to be completed by 2014 or 2015 instead of 2025 or 2030. A Salt Lake Tribune poll conducted in June showed 60 percent support for the $890 million bond. A later Deseret Morning News poll showed the same support for a sales-tax increase to pay for transit.

The Salt Lake County Council also passed a resolution to substitute sales tax increases for property taxes should the Legislature authorize it.

The Chamber opposes any property tax increases, arguing they fall disproportionately on businesses. On the other side are those who say sales taxes unfairly burden those with lower incomes and aren't as reliable as property taxes to pay off bond debt.