Browsing by Author "Freedman, Zachary Sebastian"

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Analyzing the effect of passing-lanes on rural two-lane highway operations
(Montana State University - Bozeman, College of Engineering, 2009) Freedman, Zachary Sebastian; Chairperson, Graduate Committee: Ahmed Al-Kaisy
Two-lane highways make up 80% of roads in this country. Rural two-lane highways are unique in they are typically characterized by high-speeds and low volumes. Level-of-service is associated with the proportion of vehicles stuck in platoons, or the percentage of vehicles impeded by a slow-moving vehicle. The Highway Capacity Manual 2000 (HCM 2000) recommends determining the percentage of vehicles stuck in a platoon using a performance measure called Percent Time Spent Following (PTSF). Because PTSF is nearly impossible to measure in the field, the HCM has proposed two methods for estimating its value. However, there are inconsistencies between the two methods. This limitation has led researchers to seek more appropriate performance measures for two-lane highways. When performance on these highways deteriorates to the point of needing an upgrade, the addition of a passing-lane is considered. A passing-lane is an extra lane in one or both directions of travel. The current design standards for passing-lanes (length and frequency) are based on simulation research conducted more than 20 years ago. The purpose of this thesis is to analyze traffic stream characteristics within and around a passing-lane as to improve design standards. Three appropriate performance measures were used to analyze data from two passing-lane sites in Montana. The purpose of this analysis was to determine passing lane effective length. The results showed this value may be greater than 6.6 miles. Lane use within a passing-lane section was also investigated. Traffic counters were placed at pre-determined locations within a passing-lane and data were recorded. Analysis of the data showed that aggressive drivers in the left lane are able to drive at 10 miles-per-hour faster than they were traveling as they entered the three-lane section. Further analysis showed that nearly all passing maneuvers of slower vehicles were conducted in the first 1/2-mile of the passing-lane. This thesis found the most appropriate performance measures for investigating passing-lanes are Percent Followers, Percent Impeded, and Follower Density. Also, the required spacing of passing-lanes on a two-lane highway may be farther than the current standards recommend. Lastly, for the site investigated a 3/4-mile long passing-lane would have been adequate.
Empirical examination of passing lane operational benefits on rural two-lane highways
(North Dakota University : Upper Great Plains Transportation Institute, 2010) Al-Kaisy, Ahmed; Freedman, Zachary Sebastian
This paper presents an empirical investigation into the operational benefits of passing lanes on rural two-lane highways. Two study sites in the state of Montana were used in this investigation. Performance was examined at a single location upstream and multiple locations downstream of the passing lane at each study site. Using percent followers as a performance measure, operational benefits right after the passing lane ranged between 33% and 42% at one study site and 12% to 19% at the other study site under prevalent traffic levels. Study results also suggest that operational benefits persist for a remarkable distance beyond the end of the passing lane.
Investigation of performance and lane utilization within a passing lane on a two-lane rural highway
(Scientific & Academic Publishing Co., 2013) Al-Kaisy, Ahmed; Freedman, Zachary Sebastian
An investigation into platooning and passing maneuvers within a passing lane section on a rural two-lane, two-way highway was considered in this study. The study site was located on US Highway 287 between the town of Townsend and the City of Helena in the state of Montana. Traffic volumes at study site, while considered relatively low, were typical on two-lane highways in many rural states. Per-lane analysis of performance measures and lane utilization (volume split) were used to indirectly examine passing maneuvers and lane changing at successive locations within the passing lane section. For the case study site, it was evident that traffic performance became relatively stable beyond half a mile into the passing lane for the traffic volumes investigated. Therefore, results strongly suggested that most passing maneuvers already took place before the 0.5-mile station and that the actual passing lane length was well beyond the optimal length required for breaking up platoons and improving performance.