Channelized right-turning lanes at signalized intersections : a review of practice and an empirical study
Roefaro, Sommer Ann
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This research includes a review of the current literature and practice regarding channelized lanes for right turns and the selection of an appropriate traffic control device. The main goal is to gain a better understanding of channelized right-turning lane guidelines used in practice and the effectiveness of a signal control device to regulate access at the channelization. This thesis presents a literature review and survey investigation into the current practice, the type of traffic control used, and the safety experience of highway agencies. Additionally an empirical study was conducted to examine the driver behavior at channelized right-turn lanes using raised (curbed) islands, where an exclusive signal control is used for the channelized traffic movement. The literature review revealed an overall lack of knowledge concerning the operational and safety aspects of channelized right turn lanes, especially concerning the type of traffic control used. This may explain, to a large extent, the lack of guidance in practice and the broad range of behaviors demonstrated by drivers during the field investigation. The survey results suggest a heavy reliance on engineering judgment by highway agencies in the use of channelized right-turn lanes and the selection of traffic control. Further, results confirmed a general perception in practice about the safety benefits of signal control at channelized right-turn lanes, despite the fact that such benefits were not supported in the literature. Three study sites in the cities of Belgrade and Bozeman in southwest Montana were investigated for the empirical study with approximately seven days of data for the analysis. The three study sites used a signal as the control for the channelization. The results of the investigation showed that over half of the drivers using the channelized turn lane treated the traffic signal as a yield control, while only a very small percentage of drivers treated the situation as a signal control. Further, statistical analyses confirmed that drivers' treatment of control is influenced by light conditions, vehicle type and traffic volume. This research emphasizes the need for further research into the safety and operational aspects of this right-turn treatment at intersections, particularly the type of control used for the channelization.