Performance measures are needed to inform decisions regarding the overall level of resources to devote to transportation, where to allocate these resources, and how best to use them. The first two types of decision require regular monitoring of the system to reveal problems, which present opportunities for improvement. A few, easily measured indicators of the major benefits and costs of the system are appropriate for this task. For the third type of decision, how to best address a specific problem, a more comprehensive set of benefits and costs must be considered. Indicators must be found...