A letter report issued by the Government Accountability Office with an abstract that begins "The U.S. Border Patrol, part of the Department of Homeland Security's Customs and Border Protection (CBP), operates checkpoints on U.S. roads, mainly in the southwest border states where most illegal entries occur. As part of a three-tiered strategy to maximize detection and apprehension of illegal aliens, Border Patrol agents at checkpoints screen vehicles for illegal aliens and contraband. GAO was asked to assess (1) checkpoint performance and factors affecting performance, (2) checkpoint performance measures, (3) community impacts considered in checkpoint placement and design, and (4) the impact of checkpoint operations on nearby communities. GAO work included a review of Border Patrol data and guidance; visits to checkpoints and communities in five Border Patrol sectors across four southwest border states, selected on the basis of size, type, and volume, among other factors; and discussions with community members and Border Patrol officials in headquarters and field locations."