For reasons both environment- and wallet-related, motor scooter ridership is zooming (along with transit and bike ridership, natch). Between 1997 and 2007, annual sales of new scooters jumped from 12,000 to 131,000. Scooter sales in the first three months of 2008 were up 24 percent over the same time period last year, and sellers are having trouble keeping scooters in stock. But engine-powered two-wheelers don’t get a full embrace from purists. “While scooters are better than cars from a spatial-efficiency and pollution standpoint, they are noisy, still somewhat polluting (especially two-stroke engines) and they still make streets less safe for bicyclists and walkers,” says a spokesperson for advocacy group Transportation Alternatives. “If someone is really looking to make the shift away his/her car, we’d rather they go the whole nine yards.”