accident investigation by location sampling, in which accident reports from groups of similar road sites were pooled to identify common hazards, showed that at many crossroads, over-running of the major carriageway from the minor road was an accident hazard at levels of traffic flow below that which would warrant full scale improvement work. the subject of this report is the effective development, from the basis of the location sampling study, of a low-cost improvement for straight-through rural crossroads. for the experiment a sample of thirteen crossroads was selected on class a and b roads in as many counties of england and scotland. the experiment consisted of installing traffic islands in the minor road approaches, extending minimally to the left of the centre lines so as to discourage driving straight through the intersections, and to alert drivers, causing them to take appropriate action. analysis of accidents reported over periods of four years before and four years after installation of the islands showed a significant reduction of 49 per cent of the total of accidents which would have been expected after allowing for external changes. the total cost attributable to the experiment is estimated to have been 19000. during the 'after' period of four years (1972-5) the saving of accidents is conservatively estimated to have been: 5 fatal, 15 serious and 20 slight injury accidents, representing a saving of 200000 at 1972 prices.(a)

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