By a vote of 62-38, the Senate has just passed a one-month extension of the 2005 transportation law, which was set to expire at midnight tonight and leave state DOTs without a steady source of funding for road, bridge, and transit projects.

But the one-month stopgap, which was approved by the House last week, does not address the imminent cancellation of $8.7 billion in spending authority for state DOTs — an issue that has sparked intense lobbying by highway officials as well as local governments.

For the $8.7 billion to effectively return to the states’ coffers, the Senate would need to pass the House’s three-month extension of transportation law and add on language that transfers new money from the Treasury.

But even if the Senate agreed to the three-month measure before its session ends tonight, the House would then need to approve the new spending. Prospects for both votes occurring before the fiscal year ends appear dim, given that the House clerk reported winding up legislative business earlier today.

So what happens to the $8.7 billion — and how deeply does the cancellation affect the states? The answer may not become clear until the witching hour this evening.