This report describes a comprehensive programme of measurement of saturation flow at traffic signals, and the development of prediction formulae which update those published by Webster and Cobbe in 1966, since when many factors have changed. Data were collected at 64 public road sites in UK, and the formulae based on them cover the influence on saturation flow of lane width, traffic composition, lost time, and gradient, inter alia, and deal with opposed and unopposed right-turning traffic movements. The saturation flow given for a non-nearside lane of width 3.2 m is 2080 pcu/h, some 15 per cent higher than that implied by Webster's work for his 'normal' sites. (A)

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