The automobile offers convenience, privacy and independence. Disadvantages are parking, traffic jams and other well-known annoyances. Public transit does away with traffic jams and parking and offers a green alternative to gas-burning vehicles. But the public-transit experience lacks privacy, independence and personalization. However, Heathrow airport, London, is constructing a system of PRTs, or "Personal Rapid Transit" vehicles that offer point-to-point travel throughout the airport for four passengers and their baggage. The vehicles bypass stations to arrive at the selected destination. The initial phase of the project moved from construction to operational testing last July, and will deploy only 21 PRTs that will run among three stations.

Photo credit: Advanced Transport Systems Ltd. www.atsltd.co.uk