Roberts said the governor's approach includes "every mode," including mass transit. Separating out mass transit, she said, "is not an approach we chose to take."
Democratic lawmakers, as well as Senate Republicans, say mass transit must be part of the deal.
"Democrats would not find themselves in league with any bill that left out a large component of transportation," McGeehan said. "It's the lifeblood of big cities."
Saylor said some other issues under consideration in Corbett's transportation plan had been whether to devote a significant portion of the new tax revenue to paying off the Pennsylvania Turnpike's $450 million-a-year obligation to the Transportation Department.
Some lawmakers support phasing in the gas tax increase over several years, as opposed to imposing the full $1.9 billion in the first year, Saylor said, and some support raising money through fee increases.
Other potential changes could be consolidation and privatization of some bus routes, and the use of public-private partnerships to pay for roadwork, Saylor said.