Search

Mega elliptical roundabout is a new intersection on rural multilane highways. This intersection was developed in a previous paper using simulation data, and the authors found that it is better than interchange (full cloverleaf) in most scenarios of traffic flow. Basically, there are no guidelines or procedures for designing mega elliptical roundabout in AASHTO Green Book, Federal Highway Administration guides, and Highway Capacity Manual. Thus, the purpose of this study is to analyze the traffic operation performance and propose a methodology for calculating the capacity of mega elliptical roundabout and also the level of service by gap acceptance theory. Moreover, this research studied the influence of different values of truck ratios and also different values of a major highway speed on geometric design and traffic operation performance for mega elliptical roundabout. To validate the thoroughness of the proposed methodology, VISSIM simulations were conducted. This research will assist practitioners in determining the appropriate geometric design, assessing mega elliptical roundabout intersections, and making comparisons with other alternatives., 1. Introduction The designs of conventional intersections cannot often relieve congestion without incurring increased conflicts and also significant improvement costs. Thus, there is a great need for alternative intersections offering [...]

In this study, we investigate the spatial distributions of the internal structures in semirigid base materials (SRBMs) and explore their effect on the service performance of the SRBMs. X-ray computed tomography (X-ray CT) was used to conduct a spatial voids structure analysis. Three variates were selected to study the factors influencing the spatial distributions of the internal structures, including freeze-thaw cycles, curing time, and cement content. The results show that, with the increase in the number of freezing and thawing cycles, the average porosity, void area, and void number of the SRBM samples increased, and the average void diameters of all samples initially increased and then decreased. These trends led to an increase in the mass loss ratio and strength loss ratio. Increasing the cement content and extending the curing time decreased the average number of voids, average void area, and average void diameter and decreased the mass loss ratio and strength loss ratio of the SRBMs. The top and bottom of the SRBM samples were more porous than the middle of the samples, whereas the maximum value of the average void diameter was observed in the middle of the samples. [ABSTRACT FROM AUTHOR]