Safe Routes to School Expansion Act This bill expands eligibility under the Highway Safety Improvement Program to include certain safety projects related to safe routes to school infrastructure improvements such as sidewalks, crosswalks, signage, bus stop shelters or protected waiting areas. The bill increases the federal share for the Department of Transportation (DOT) to fund improvements for pedestrian or bicyclist safety, safety of people with disabilities, and safe routes to school infrastructure. DOT must also carry out a safe routes to school program for the benefit of children in primary, middle, and high schools.