A zebra crossing is a type of pedestrian crossing used in many places around the world. A zebra crossing typically gives priority to rights of way to pedestrians. Although the origin of the name is disputed, it is generally attributed to British M.P. James Callaghan who, in 1948, visited the country's Transport Research Laboratory which was working on a new idea for safe pedestrian crossings. On being shown a black and white design, Callaghan is said to have remarked that it resembled a zebra. Crossings were originally marked by beacons and parallel rows of studs. After isolated experiments, the zebra crossing was first used at 1000 sites in the United Kingdom in 1949 and a 1951 measure introduced them into law.