Two senators wrote Transportion Secretary Ray LaHood asking for an evaluation of the the "cash for clunkers" program before the Senate takes up a vote to extend the program's funding this week.

Sens. Dianne FeinsteinDianne FeinsteinOvernight Defense: Armed Services chairman's hopes for Trump | Senators seek to change Saudi 9/11 bill | Palin reportedly considered for VA chief Lawmakers praise defense bill's National Guard bonus fix CIA head warns Trump: Undermining Iran deal would be 'disastrous' MORE (D-Calif.) and Susan CollinsSusan CollinsSenators crafting bill to limit deportations under Trump Cornyn: ‘Virtual certainty’ Sessions and Price will be confirmed Trump's wrong to pick Bannon or Sessions for anything MORE (R-Maine), two principal authors of the initial bill, asked LaHood for key statistics on the number of cars purchased under the program, and the extent of the environmental impact expected to be gained by the program.

"We believe that Congress needs this information immediately in order to evaluate the program's effectiveness in attaining its two goals of stimulating automobile sales and reducing oil consumption," the senators wrote. "Without strong data on the effectiveness of the program, it will be more difficult for Congress to evaluate and improve the current program."

The extension of the program may face a bit more of an uphill climb in the Senate compared to the House, which easily passed the fast-tracked bill. Sen. John McCainJohn McCainA Cabinet position for Petraeus; disciplinary actions for Broadwell after affair Meet Trump’s ‘mad dog’ for the Pentagon Wrestling mogul McMahon could slam her way into Trump administration MORE (R-Ariz.), for instance, pledged to filibuster an extension.

(Hat tip: SenateUS)