Consider the trolleybus

Comment to Randal O'Toole's Driving Bounces Back:

The trolleybus. Contrary to a train or a tram, a trolleybus does not need rail infrastructure. This not only results in huge cost and time savings, it also saves a large amount of energy in construction. 

Granted trolleybuses cant go everywhere but with no need for rail and city grid streets they can accommodate a vast multitude of sites and locations. 

Quito, Ecuador has a trolleybus system. During peak hours, there is a bus every 50 to 90 seconds (because of the high frequency, there are no schedules). "El Trole" as it’s called, transports 262,000 passengers each day. 

By choosing the cheap trolleybus over tram or metro or light rail, Quito developed a large network in a short time. The capital investment of the 19 kilometre line was less than $60 million dollars. Hardly sufficient to build 4 kilometers of tram line, or about 1 kilometer of a metro line. 

Light rail in the US now costs about $100 million per mile. Portland's Milwaukee line cost $200 million per mile. Lower investment costs also mean lower ticket fares, and thus more passengers. The Milwaukee line cost $1.5 BILLION. For that Portland could have built 294 miles of trolley bus service. Enough to move several times it’s population.