In this report, an experiment to assess the effect of equipping a length of motorway with 70 mph repeater signs upon vehicle speeds is described. The site chosen was a 20 mile section of the northbound carriageway of the M1 motorway terminating at junction 37 in Yorkshire. Standard design 70 mph signs, 900mm in diameter were installed at 1 mile intervals on both the nearside verge and in the central median starting 20 miles south of junction 37. Data were collected from automatic census equipment, which counted, classified and measured the speed of all vehicles every fourth day. Data from the northbound carriageway were compared with that from the unsigned southbound carriageway. Similarly data from the year before the signs were unveiled on 1 September 1988, was compared with data for the year after. Multiple regression analyses were carried out to determine those factors affecting traffic speeds. Data analysis revealed that there was no evidence that the signs had any significant effect on the speeds of cars, rigid heavy goods vehicles (HGV's), buses or coaches. For medium goods vehicles and articulated HGV's some speed reduction was noted, however this might be attributed to undiagnosed faults in the measuring equipment for four months of the study.

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