Sarah Debbink Langenkamp Active Transportation Safety Act This bill amends the Highway Safety Improvement Program (HSIP) to include additional bicyclist and pedestrian safety measures and increases the federal cost share for certain safety projects. Specifically, the bill allows HSIP to fund projects (1) for the connection of two or more segments of existing bicyclist or pedestrian infrastructure, or (2) that are based on a state's plan to improve the safety of vulnerable road users (e.g., bicyclists or pedestrians) in areas identified as high-risk. In addition, the bill allows an increased federal cost share of up to 100% for these projects. The bill also allows an increased federal cost share of up to 100% for certain transportation projects that include a Federal Highway Administration Proven Safety Countermeasure for bicyclists or pedestrians. These measures include bicycle lanes, walkways, and crosswalk visibility enhancements.