Discussion on Papers 12–14

Mr R.J. POTTER {Consultant, Wootton, Jeffreys & Partners): Over the past two years we have used helicopters and aerial photography for collecting traffic data. We overcame the problem of transforming the photographs by employing a photographer to lean out of the helicopter to adjust for the drift and rotation of the helicopter. We found, as did Dr Mountain, that having to pay commercial rates for computer time made automated data-reduction methods uneconomic. The data obtained by this method is very valuable as it provided route information as well as origin-destination information. This technique has only been used for data collection in city centres because of the limited area that can be covered.