This paper initiates the study of scaling laws for vehicular ad hoc networks (VANET)s. It provides a general framework to study VANETs. The fundamental capacity limits of these networks are investigated and we show how the road geometry affects this capacity. The VANET capacity is calculated for different road structures. The need for new capacity metrics is dis- cussed. These results are obtained by combining geomet- rical analysis, network flow arguments, and probabilistic study of VANETs.