Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
3 results
Search Results
Item An investigation of operational performance on two-lane highways(Montana State University - Bozeman, College of Engineering, 2018) Jafari, Amirhossein; Chairperson, Graduate Committee: Ahmed Al-KaisyA high percentage of the US road networks are two-lane highways. The Highway Capacity Manual (HCM) is the standard reference used in the US for traffic analysis of such highways (HCM 2016). This manual uses a qualitative measure called 'Level of Service (LOS)' to show the quality of traffic flow on the highway network. Performance measures are used as indicators of the LOS in the HCM. The current manual uses Average Travel Speed (ATS), Percent Time Spent Following (PTSF), and Percent Free Flow Speed (PFFS) for measuring LOS on two-lane highways. However, several studies reported that the HCM methodology falls short in several aspects including the performance measure used for operational analysis on two-lane highways. Moreover, the current guidelines of the HCM regarding passing lanes are very limited and based on studies conducted more than three decades ago (Harwood and St. John 1985, 1986). Constructing a passing lane is expensive and there is a need to use accurate methods for the design of such facilities. Therefore, the goal of this study is to examine new performance measures for operational analyses of two-lane highways as well as developing new guidelines for the design of passing lanes. Multiple investigations were conducted using field data from four states in the US as well as microscopic traffic simulation software, SwashSim. Using field data and statistical analysis as well as the results of a survey, the most appropriate performance measures were selected. Additionally, traffic simulation software was used to investigate the operational improvement of passing lanes. Optimum length and effective length of passing lanes were investigated. Optimum length has been used to refer to the length that would bring most operational benefits given the amount of passing lane investments while effective length is defined as the length of two-lane highway over which the effect of a passing lane extends. Moreover, the operational efficiency of different passing lane design configurations were examined to identify the most appropriate length and spacing to be used in the planning and design of passing lanes. In addition, the operational performance of 2+1 roads was investigated in this study and some guidelines for design of these facilities are provided. 2+ 1 highways have one lane in each direction of travel and the middle lane alternates between the two directions.Item Empirical assessment of a congestion and weather-responsive advisory variable speed limit system(Montana State University - Bozeman, College of Engineering, 2016) Siddiqui, Sohrab; Chairperson, Graduate Committee: Ahmed Al-KaisyTraffic congestion and safety along urban corridors have become major challenges for most highway agencies in the United States. Adverse weather conditions also present a considerable challenge, both in terms of safety and operations. All these problems along with the increasingly limited resources for infrastructure expansion have urged transportation agencies to investigate innovative traffic management approaches. One of these approaches is the use of Active Traffic Management (ATM) strategies. Within ATM, the practice of Variable Speed Limit (VSL) systems is well suited to improving safety and operations. These systems dynamically utilize real-time traffic and/or weather data to post appropriate speeds that are thought to improve safety and operations along a corridor. The overall aim of this thesis is to investigate the benefits of a recently installed advisory VSL system along OR-217 freeway in Portland, Oregon. This corridor is characterized by high traffic levels, severe congestion and unreliable travel times. The congestion of the freeway contribute to crash rates exceeding the statewide averages for this type of facility. Pacific Northwest's unpredictable climate presents another challenge that doubles the congestion and safety problems along the corridor. The effectiveness of this system was explored through an in-depth 'before and after' and 'on-and-off' analyses. The study was designed in a way that it encompasses both the safety and mobility benefits of the system. Besides, driver compliance with the system was also measured under different scenarios. The results indicated that the system had significant impacts on both mobility and safety. In terms of mobility it was found that system had lowered the average speeds along the corridor. The advisory VSL activation also resulted in reduced capacities. Safety assessment of the system suggested that, VSL has decreased crash rates and temporal and lateral variations of speed. Under certain scenarios, the system also decreased the longitudinal variations of speed. Further, it was also found that due to the advisory nature of the system, the majority of drivers do not comply with the system. However, VSL has resulted in reducing the percentage of aggressive drivers and have increased the number of drivers complying the static speed limit.Item Channelized right-turning lanes at signalized intersections : a review of practice and an empirical study(Montana State University - Bozeman, College of Engineering, 2011) Roefaro, Sommer Ann; Chairperson, Graduate Committee: Ahmed Al-Kaisy; Patrick McGowen (co-chair)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.