U.S. Rep. Jared Polis said Thursday he has a great idea of how the Regional Transportation District can spend $134 million it expects to save from refinancing loans that helped pay for Denver Union Station’s transit center.

Polis, a Boulder Democrat, on Thursday said he thinks RTD should use the money as a “down payment” on completing the B commuter rail line beyond its current terminus in Westminster to Boulder and Longmont, as the mass transit agency pledged to do in 2004 as part of the…