Plans prepared during the 1960s for transit improvements in such diverse cities as Pittsburgh, Seattle, Edmonton, Amsterdam, Johannesburg and Bangkok considered only the enhancement of bus services and construction of a conventional metro. Similar plans prepared today include a greater number of potential modes, with light rail transit (LRT) increasingly selected as a favoured choice for busy corridors and networks. New LR T lines or networks are already operating in Buffalo, Calgary, Edmonton, Manila, Nantes, Newcastle-upon-Tyne, Rio de Janeiro, San Diego, Torino, Tunis and Utrecht-a list that could no doubt be extended depending on accepted definitions of 'new' and 'LRT'. At least a dozen entirely new networks arc under construction, as in Sacramento and Grenoble, and many more are being adapted from existing tramways as in Charleroi. A similar number of LRT systems arc at the planning stage, including the 258 km Dallas network and lines in such cities as Los Angeles, Buenos Aires and Kuala Lumpur. What has brought about such a drastic change in transit planning in less than two decades?