Scholarly Work - Civil Engineering
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3460
Browse
3 results
Search Results
Item Measuring Performance on Two-Lane Highways: Empirical Investigation(2017-01) Al-Kaisy, Ahmed; Jafari, Amirhossein; Washburn, ScottThis paper presents an empirical investigation into several performance measures for operational analysis on two-lane highways. The performance measures investigated are average travel speed, average travel speed to free-flow speed, percent followers, followers flow, followers density, percent impeded, impeded flow, and impeded density. Field data from 16 study sites in the states of Montana, Idaho, Oregon, and North Carolina representing Class 1, Class 2, and Class 3 highways were used in this study. The level of association between performance measures and some of the most important traffic variables was examined with graphical and statistical techniques. The traffic variables investigated in this study included combined flow in both directions of travel; proportion of traffic in the direction of travel, called in this study “traffic split”; percentage of heavy vehicles; and speed variance. Study results suggest that speed-related measures have weak associations with traffic variables compared with headway-related measures. Further, compound measures involving headway and traffic flow or density exhibited the highest associations with traffic variables. With regard to two-lane highway type, higher associations are exhibited at Class 1 sites compared with Class 2 and Class 3 sites. Performance measures showed the highest associations with combined flow and traffic split.Item Traffic Operations on Rural Two-Lane Highways: A Review on Performance Measures and Indicators(2018-05) Al-Kaisy, Ahmed; Jafari, Amirhossein; Washburn, Scott; Lutinnen, Tapio; Dowling, RichardTwo- lane highways constitute a large proportion of the highway system in the United States, particularly in rural areas. Performance evaluation on those highways is the basis for planning, upgrade, and improvement programs. Such evaluations are conducted using performance measures that should ideally be correlated to performance determinants on those highways. Unlike other highway facilities, two-lane highway performance is notably affected by the platooning phenomenon, which is believed to be a function of traffic level and passing opportunities. Over the last couple of decades, several studies have addressed performance measures on two-lane highways, and are mainly driven by the reported limitations of the current measures used by the Highway Capacity Manual (HCM). This review aims to summarize the performance measures that have been published in the literature or used in practice both in the United States and abroad. The review starts with an historical overview of the HCM performance measures since its inception in 1950. It then discusses the most important criteria for measures to be more effective in describing performance, before presenting the review results for measures that have been proposed in literature or reported as being used in practice. Finally, a subjective assessment of all performance measures against the set of criteria outlined in the article is presented. The review presented in this paper provides information that is valuable for practitioners and researchers in understating the alternative measures for assessing performance on two-lane highways, and the limitations and merits associated with those measures.Item Performance measures on two-lane highways: Survey of practice(2018-11) Al-Kaisy, Ahmed; Jafari, Amirhossein; Washburn, Scott; Lutinnen, Tapio; Dowling, RichardTwo-lane highways constitute a significant component of the highway system and serve an essential function for the movement of people and goods. The Highway Capacity Manual is primarily used for operational analysis on two lane highways in the U.S. and Canada. As part of a project sponsored by the National Cooperative Highway Research Program for improving two-lane highway operational analysis methodology, a practice survey was conducted to gather information on agency experiences in regards to performance measurement on two-lane highways. The survey was sent to all state Departments of Transportation in the United States and Canada. A total of 35 usable responses were received, representing 25 states and 4 Canadian provinces. This paper summarizes the results of the agency survey and presents the most important findings. Results suggest that the top three criteria for good performance measures are: sensitivity to traffic conditions, sensitivity to road conditions, and relevance to road user perception. Further, agencies identified average travel speed as the most relevant traffic flow aspect to two-lane highway operations. Other performance measures that were found meritorious were volume-to-capacity ratio and flow rate, for class I and class II highways, respectively, versus the latter measures and percent-time-spent-following for class III highways.