Cities around the world are looking to reduce greenhouse gas and other emissions from vehicles through the use of low emission zones and congestion pricing. These strategies have been employed to great success abroad, including in central London, where both congestion pricing and fees and restrictions on higheremitting vehicles are in effect. In the U.S. law context, these policy approaches give rise to significant legal issues that have not been well-explored. This Article proposes that these policy approaches be called “Low Traffic Zones” (LTZs), and surveys those legal considerations. The areas of law explored are: (1) potential for preemption of LTZ policies by U.S. federal laws; (2) U.S. constitutional considerations; (3) federal tolling authority; (4) state enabling laws; (5) laws to protect individual privacy and data security; and (6) other claims that may be raised in litigation. It concludes by outlining guidance U.S. lawmakers and policymakers may take into account in drafting LTZ policies to comport with U.S. and state law.