We are at a critical time in our history as a species. We are failing to use the resources we have sustainably, polluting our planet in dangerous ways, and beginning to lose some of the huge health gains we have made in recent history. However, many of our environmental and public health problems can be solved through low-cost investments in urban transit. This paper will explore the problems we face, investigate what goes into an effective urban transit system, compare the different modes of transit available to a city, and discuss complementary interventions. Case studies will be used to provide examples of real-world transportation successes and failures. The argument for urban development being superior to suburban or rural development for future sustainable growth will also be made.