Under DC law that is technically a motorcycle. Because it’s both illegally parked on the sidewalk and has expired registration it should be impounded. I would call MPD, DPW and fill out an abandoned vehicle request at 311.dc.gov [see the right side-bar under ‘Special Services – Abandoned Vehicles’.] Get a confirmation number and follow up with them if it’s not removed in a few weeks. If you still get no response try the MPD Yahoo list-serv for whatever police district it’s located in. Often DPW heads or DC Council staff monitor these list-servs and will then get involved when needed.