Mailmen on Scooters? Seeking to discover whether big-city streets or bumpy country roads can keep mail carriers from their appointed rounds, the U.S. Postal Service said on Tuesday it is set to expand testing of the much-anticpated Segway Human Transporter scooter into six cities. The initial tests demonstrated how the machines could relieve postal workers from the travail of carrying up to 35 pounds of mail along their routes, the post office said. It also decreased the time it took to walk between delivery addresses.