This document discusses a network-based approach to taxi sharing in New York City. It analyzes large GPS data sets of taxi movements to understand urban taxi systems and trips that could be combined. A new dispatch algorithm is proposed that can combine multiple trips into "Taxi Limousines" to make the system more efficient and reduce emissions. Simulations show that with only a 1 minute initial waiting time, most trips in NYC can be combined for taxi sharing. An online tool called HubCab is being developed to interactively explore the data.