This project measured and documented the effect that snowplowable raised pavement markers (SRPM's) have on the behaviour of traffic at certain geometric highway conditions. Two lane rural curves, highway exits with deceleration lanes and highway bifurcations were studied. Measures of performance selected to study the effects of the markers were: erratic manoeuvres such as cutting through painted gores, weaving between exiting lanes, center and edge line encroachments; point of entrance into deceleration lanes; and mean speeds and speed variance at curves. All types of erratic manoeuvres studied were significantly reduced at various sites for traffic volumes up to 500 veh/hr lane. At volumes between 900-1000 veh/hr/lane, the markers had no effect on traffic. Raised markers were not successful in causing motorists to enter deceleration lanes at exits earlier. As far as speeds, the markers seem to have abrupt speed changes. The effect of SRPM's on speed variance was inconclusive. The markers were effective in reducing erratic manoeuvres at sites with and without overhead lighting. At one site, a high rate of erratic manoeuvres during rain conditions was not only significantly reduced with the placement of markers, but the wet condition EM rate with the markers approached the quality of the dry condition rate. A visual analysis of 15 different layouts of raised pavement markers at exits with deceleration lanes was performed and led to the placement of the devices on the gore at 20 ft., lane lines at 40 ft., and edge lines at 40 ft. spacings.
Abstract