Enforcing border controls can create long queues for travellers, David Crawford looks at potential solutions. Long delays at border crossings in both North America and Europe have sparked the development of new queue visualisation and management technologies that are cutting hours, even days, off international passenger and freight journeys. At the westernmost end of the 2,019km (1,250 mile) Mexico–US frontier, two parallel crossings between Tijuana, in the former country, and the border city of San Diego,