Metro had planned to give a private company the responsibility for maintenance and upgrades in exchange for the rights to collect parking fees. But there were concerns about the plan.

WASHINGTON — Metro has canceled a request for proposals to privatize its parking lots.

Documents related to the procurement, dated Thursday, say that Metro must re-evaluate the requirements.

The deadline for proposals had previously been extended until December.

When Metro published the initial formal request in September, it hoped to find a way to give a private company the responsibility for maintenance and upgrades in exchange for the rights to collect parking fees.

General Manager Paul Wiedefeld included privatizing parking on his list of potential management changes for Metro back in March.

Concerns about the proposal included whether there could be a conflict between maximizing parking revenue and maximizing the number of people who take the train rather than joining D.C. area traffic jams.