6. Salt Lake City, Utah (tie)
Salt Lake City earns its No. 6 spot in large part because of its heavy investment in serving a large suburban and exurban population. The Utah Transit Authority is expanding its light rail system, known as TRAX. The city is adding four new lines to the three-line system, allowing better suburban access to the city; though the city’s population is just over 180,000, the system serves 1.7 million people in the larger area.