Abstract
The efficiency and safety of type-A freeway weaving sections in urban areas are constrained by recurrent bottlenecks. Limited space in freeway weaving sections cause traffic congestion and crashes during peak-hours. Various factors, including length of weaving section, continuity of lanes, and number of lanes will have significant effects on the level of service and safety performance of the weaving sections. Eight years (2010-2017) of crash data in the type-A weaving sections was used in this analysis. The objective of this study aims to evaluate geometric design factors and operational factors on total crashes and each of the four crash types: rear-end, sideswipe, angle, and single-vehicle in type-A weaving sections using traditional negative binomial approach and develop crash modification factors (CMFs) to improve safety in the type-A weaving section. The results revealed that on-ramp traffic per hour, off-ramp traffic per hour, non-weaving traffic per hour, weaving ratio, length of the weaving section, direction of the freeway, width of inside shoulder, and width of outside shoulder were influencing crashes in type-A weaving sections. Furthermore, the estimated crash modification factors (CMFs) result revealed that total crashes gradually decrease as inside shoulder width increases. This implies that widening inside shoulder width have positive effects on weaving section safety. In addition, ramp metering, and advisory warning signs could improve safety in type-A weaving sections.
Highlights
Since late 1960’s, weaving areas have been a subject of great deal of research yet crashes on freeway weaving sections in urban areas continue to increase
The objective of this study aims to evaluate geometric design factors and operational factors on total crashes and each of the four crash types: rear-end, sideswipe, angle, and single-vehicle in type-A weaving sections using traditional negative binomial approach and develop crash modification factors (CMFs) to improve safety in the type-A weaving section
The authors from this study revealed that weaving sections with longer lengths will have lower crash frequency per 1000 feet, increase in lane changes for diverging vehicles will result in more crashes in the freeway weaving sections, increasing merge traffic in the weaving sections will slightly reduce the crash risk, and increasing diverge traffic in the weaving sections will increase the crash risk (Qi et al, 2014)
Summary
Since late 1960’s, weaving areas have been a subject of great deal of research yet crashes on freeway weaving sections in urban areas continue to increase. Weaving sections on freeways experience higher crash probabilities compared to basic freeway section according to National Highway Safety Administration, (2009) and (Pulugurtha and Bhatt, 2010). On Memorial Parkway freeway in City of Huntsville, Alabama, the weaving sections have a higher crash rate of 37.32 crashes/mile/year compared to other typical freeway crashes having a crash rate of 14 crashes/mile/year within the same county in Alabama. This shows that safety of weaving sections is of concern. The geometric design factors include length of weaving section, lane width, left shoulder width and right shoulder width. The operational factors include on-ramp volume, off-ramp volume, weaving volume, basic freeway volume, non-weaving volume and weaving ratio
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