As of 2003 it has about 30,000 members in the UK and 2,000 members in Ireland. While principally a union for people in the railway industry, the effect of the nationalisation and subsequent privatisations following the Second World War has meant that it has members working for railway companies, shipping companies, bus companies, travel agencies, airlines, call centres, and IT companies. At the start of the 21st century it was aggressively recruiting new members in the travel trade, such as employees of Turkish Airlines in London.
Individual members are allocated to branches. Historically branches were organised geographically and by grade, e.g. Liverpool; Dublin No. 1; Crewe No. 4 Technical; Crewe Management Staffs (the separate branches for different grades of staff were so that people with grievances against their managers wouldn't find those same managers as members of their branch). In Ireland, branches are still organised on this basis, but in the UK starting in 1998 there was a reorganisation such that members of most branches are employed by a single company e.g. Virgin Midlands - this was required in the fragmented world of the privatised railway because the private companies would not allow access for non-employees onto their premises.
Branches are in turn allocated to divisions - there are 14 geographical divisions, plus one for London Transport. Each division has a Divisional Council which meets at least twice a year, and members in each division elect a member of the Executive Committee (EC). EC members are elected for a three-year term, subject to a maximum of two consecutive terms of office (but can stand again after 3 years off the committee). The EC meets approximately 10 times a year in London and continuously during the four-day annual conference held each May. The EC is responsible for the efficient running of the union, the employment of staff (of whom there are about 70), the oversight of the union's finances, and the implementation of decisions of Annual Conference.
The Annual Conference is the supreme decision-making body of the union. Each branch sends one delegate to the Conference, unless a branch has more than 200 members in which case it has two delegates. Each branch can submit two motions and two amendments to motions to the Conference Agenda, and once every five years can submit two amendments to the union's Rule Book.
Organisation in Ireland is slightly different. All of Ireland forms one Division. As trade union law in the Republic of Ireland forbids trades unions from being run by people not resident on the island of Ireland the EC and Annual Conference cannot directly control the association's activity in the republic as they do in Britain. Instead, the Irish Divisional Council is constituted as the "Irish Committee" and chaired by the EC member for Ireland, and it operates in a similar manner to the EC. There is a biennial Irish Conference of delegates from all the Irish branches, to set policy solely relating to Ireland. When Irish branches want the Annual Conference to do something, motions to Annual Conference are normally phrased as 'requests' that the Irish Committee consider doing something rather than as the more normal 'instructions' that the Executive Committee do something.
The early years were difficult. The third General Secretary, John Stopford-Challener, shot himself in Paris's Bois de Boulogne in 1906; it was only after his suicide that it was discovered that he had absconded with the union's money. After this came the era of A.G. Walkden, who as General Secretary for 30 years led the union to the peak of its influence; the head office in London, built in the early 1960s, is named after him. The railway companies refused to recognise the trade unions until after the strike of 1919, but after that time membership rose steadily, to a peak of some 91,500 in the early 1950s. The subsequent closure of uneconomic railway lines, the Beeching axe, and especially the computerisation of railway offices led to large scale reductions in the eligible membership. Membership was around 75,000 in 1970, 71,000 in 1980, and 39,000 in 1990. There was a rapid loss of around 25% of its membership in the mid to late 1990s because the grades of staff covered by the union were the ones hardest hit when British Rail was broken up from 1994 onwards; however the Executive Committee adopted a policy of seeking to vigorously recruit additional members particularly in those areas such as travel agencies which had not been the principal focus of the union in the past. This has led to more stable membership figures, including a small increase at the turn of the century.