Assessment of Operational and Safety Impacts of Various Traffic Control Devices PDF Download

Author: Megat Usamah Bin Megat Johari
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0

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Book Description
Fatal crashes have been increasing, both in Michigan and across the United States, despite continuing improvements in roadway design, vehicle safety, and other areas. Various factors may have contributed to this trend, including increased in-vehicle distractions, higher speed limits, legalization of marijuana, and other factors. Studies have suggested that driver error is a critical reason associated with more than 90 percent of all traffic crashes. Driver behavior can be improved by several engineering strategies, such as the use of better and more efficient traffic control devices, such as signs, signals, and pavement markings. To that end, this research assesses the operational and safety impacts of a series of traffic control devices.The use of dynamic message signs (DMS) as a medium to display safety messages to drivers has become popular among transportation agencies. Despite their widespread use, evaluations as to the resultant impacts on traffic crashes have been very limited. This study addresses this gap in the extant literature and assesses the relationship between traffic crashes and the frequency with which various types of safety messages are displayed. A series of count models are estimated to examine total, speeding-related, and nighttime crashes based upon historical messaging data while controlling for other site-specific factors. Ultimately the results provide important insights regarding messaging strategies for transportation agencies. This research also evaluates driver response to advisory speed signs. Posted speed limit signs are used to inform drivers of the legal maximum allowable speed. In contrast, advisory speed signs provide recommendations to drivers as to safe travel speeds at specific roadway locations. Various studies have investigated the safety impacts of speed limit changes, particularly on high-speed rural highways. One area of particular concern on such roadways is the approach to exit ramps that require substantive speed reductions, such as loop ramps. To date, there has been limited research examining the safety impact of the differential between the mainline speed limit and the lower exit ramp advisory speeds. This study addresses this gap through the estimation of a series of safety performance functions. The findings from this study show the safety of these locations is related to speed differential, as well as other factors such as the length of the upstream deceleration lane. These factors should be considered when considering speed limit policy impacts in the vicinity of full and partial cloverleaf interchanges.Lastly, this study assesses the use of dynamic speed feedback sign (DSFS) as a means to reduce vehicle speeds in speed transition zones, where speeds are reduced as drivers enter rural communities. DSFS have been evaluated in several settings, including high-speed exit ramps and horizontal curves. However, research is limited as to the effectiveness of this sign for other purposes, such as these high-speed transition areas. This is particularly important as the limits on some of these roadways have recently been increased, making speed control a particular concern. This study addresses this gap through a before-and-after evaluation of DSFS at five different sites in northern Michigan. A series of speed models were estimated, which provide insights on the effectiveness of DSFS.