Founded in 1903 and acquiring its current name in 1907, its aim was to develop motor sport through clubs and arrange touring facilities for members.
From page one of the Auto-Cycle Union Official Pocket Handbook, 1964:
Auto Cycle Union: Founded in 1903 as a Branch of the Royal Automobile Club to protect the interests of Motorcyclists and to encourage the Sport and Pastime of Motorcycling, and since 1924 has existed solely for the purpose of encouraging and controlling the Sport.
The ACU also governs the safety standards for personal protection equipment worn during racing. Only motorcycle helmets which meet ACU standards and display the appropriate ACU sticker can be worn in 'speed' competitions. The majority of quality helmets sold in the UK now feature an ACU Gold sticker and many riders choose these for everyday use in preference to those that meet the more basic BS6658:1985 legal requirement.