Examining exposure of motorcycles at signalized intersections

Abstract

Crash statistics in Singapore from 2001 to 2005 have shown that motor-cycles were involved in about 54% of intersection crashes. The overall involvement of motorcycles in crashes as the not-at-fault party was about 43%, but at intersections the corresponding percentage is increased to 57%. Quasi-induced exposure estimates have shown that the motorcycle exposure rate at signalized intersections was 41.7% even though motorcycles accounted for only 19% of the vehicle population. This study seeks to examine, in greater detail, the problem of motorcycle exposure at signalized intersections-in particular, the exposure caused by potential crashes with red-light-running vehicles from the conflicting stream. For that purpose, four signalized intersections are investigated. Results show that motorcycles are more exposed because they tend to accumulate near the stop line during the red phase to facilitate an earlier discharge during the initial period of the green, which is the more vulnerable period. At sites in which there are more weaving opportunities because the lanes are wider or there are exclusive right-turn lanes, the accumulation is higher and hence exposure is increased. The analysis also shows that the presence of heavy vehicles tends to decrease motorcycle exposure because motorcyclists' weaving opportunities become restricted and they are more reluctant to weave past or queue alongside the heavy vehicles; effects intensify for narrower lane widths.