Standard gauge (1,435 mm or 4 ft 8 1/2 in) is the world's most common railway track gauge, used in about 55% of lines and almost all high-speed rail. Its prevalence stems from historical interoperability needs, avoiding costly reloading at gauge breaks. While its origin is debated, it likely evolved from existing wagonway gauges in England, influenced by the dimensions of horse-drawn carts. George Stephenson's adoption of this gauge for major lines solidified its dominance in Britain and beyond. Despite initial variations and a "gauge war" in Britain, standard gauge ultimately prevailed due to its efficiency and interconnectivity benefits.