Institute a parking fee at all federal buildings that currently have free parking for motor vehicles. Parking fees can be patterned after the US Forest Service trail pass fees, where each site would have a self-service permit system for a daily fee, along with a longer term permit fee for yearly use. Fees could be determined using the Forest Services current fee structure - $5 per day or (is it) $30 per year.
Parking fees would encourage car pooling, use of public transportation, as well as bicycling and walking. Fees generated with this program could be applied to maintanence of the parking lots.