Less Traffic with Smart Stop Lights Act of 2017 This bill directs the Department of Transportation (DOT) to establish a Smart Technology Traffic Signals Grant Program. DOT may make competitive grants to states, local, or tribal government entities for projects to improve, through use of innovative technology, the functioning of traffic signals to reduce traffic congestion, fuel costs for drivers, and air pollution, as well as improve the safety and effectiveness of roadways. However, a grant may not be used to purchase, operate, or maintain an automated traffic enforcement system. The federal share of project costs may not exceed 80%, but DOT may waive such limit if an assisted entity can show extreme financial hardship.