Above all else, the East End grumbles about traffic on Memorial Day weekend. Routine errands are run in haste during the previous workweek or put off until Tuesday. If one does venture out, it’s as if on a polar expedition, with circling to find a spot like parking-lot polka. The traffic control officers do their best to keep things moving. Fender-benders abound. Tempers rise. “Who are these people?” we ask. “Where can they be going?” These questions may never be answered.More seriously, motor vehicles remain one of the largest sources of greenhouse gases.