The overall objective was to evaluate transportation controls to reduce motor vehicle emissions in major metropolitan areas. An appreciation of transportation controls was made, and their effectiveness in reducing emissions, their feasibility, and the probable costs were assessed. The transportation controls which could conceivably reduce motor vehicle emissions in the next few years are described and evaluated. The intent was to provide assistance in the preparation of transportation components of state implementation plans. In most of the metropolitan areas under study, overall CO emission reductions of at least 50 percent from existing levels appear required to meet the national ambient air standards by 1975. Most transportation controls that are capable of being introduced in the next few years offer the potential for only modest reductions. All controls would entail very substantial implementation costs which are discussed.