Transportation networks are high value targets for terrorists and criminals. They are widely accessible, visible, attract intense media attention and have a significant degree of government ownership. Since the 9/11 terrorist attack in 2001, transportation networks have been the focus of increasing security improvements worldwide. Much of the analytical work with respect to improved security of transportation networks has been related to the costs of the security improvements. Benefits have largely been ignored or described in general terms of community safety or the risk of terrorism to trade flows. This analysis provides a qualitative analysis of the benefits of security. An economic framework is used as a guide to develop a taxonomy of security benefits in four dimensions : sovereignty protection, terrorism prevention, interdiction of illegal activities and personal security. Direct and indirect benefits are described. The analysis shows that the benefits of transportation security measures are often more subtle and pervasive than simply providing a safer and more secure community.