Ali A Selim

Local Rural Road Safety Audit Guidelines and Case Studies

The main goal of this study was to improve the safety performance of local rural roads in South Dakota by promoting road safety audits (RSAs) and by providing a toolbox of low-cost safety improvement strategies to county highway superintendents and local highway agencies. The study conducted RSAs at 12 selected sites along county highways, city streets, and township roads. RSA projects were selected through South Dakota Local Transportation Assistance Program promotion and commitments from South Dakota local agencies. The study exposed local governments to the concept and practices of road safety analysis. The study also provided a good opportunity for local highway agency staff members to participate and gain experience by working with road safety teams. This paper reports on the procedures and the results of the rural road RSAs and identifies guidelines to conduct RSAs on local rural roads to help local agencies identify, prioritize, and implement safety improvements.

Determination of SMA Slab Properties Using a Newly Developed Roller Compactor (Turamesin)

Compaction of asphalt mixtures in the laboratory is critical to meaningful results. Over the years, several compactors were developed to closely simulate field compaction. However, none of the devices or equipment was found to effectively compact asphalt mixtures. Therefore, a new automatic roller compactor (Turamesin) was developed which is able to compact any asphalt mixtures to the required slab thickness and density. The machine was developed by researchers from the Universiti Putra Malaysia, under the Ministry of Science, Technology and Innovation. In this study, Stone Mastic Asphalt (SMA) mixture was selected. The study was carried out in order to establish criteria for slab compaction and explore the potential for the newly developed Turamesin for use in the SuperPave mix designs. A total of nine slabs were prepared with different combinations of compactive efforts. Data was collected and analyzed to determine the appropriate values of the compactive efforts that results in optimum performance of the asphalt mixture. It was observed that the compact slabs of asphalt mixture to a design air void of 4%, a compactive effort of applied pressure of 8.0 kgf/cm squared, and 75 passes of roller were required.

Analysis of Factors Causing Corrugation of Gravel Roads

Gravel and unpaved roads are viable and important components of the road transportation network throughout the world. In the United States, gravel and unpaved roads still make up close to 50% of road miles. Motorists traveling on a gravel road will encounter the problem of corrugation. Corrugation, or washboarding, is a problem with many causes and no long-term solutions, requiring continual maintenance to control its appearance. Several factors have been researched and found to contribute to corrugation, such as traffic volumes, vehicle speeds, subgrade characteristics, harmonic vibration of the vehicles suspension system, and gravel properties. This study examines the causes of corrugation by using variables previously considered by other researchers as well as new variables added by the studys research team. The objective of this study is to develop a comprehensive prediction model that can identify the potential occurrence of corrugation at a specific location. The model calculates corrugation height and wavelength. One significant and considered new conclusion is that corrugation is affected by the amount of natural soil placed between the gravel layer and the natural subgrade material. This natural soil is placed on the road surface during the original construction of the road and comes from formation of the side ditches. Another conclusion is that the moisture content of the subgrade, the ratio of the thickness of the surface gravel to the depth to the subgrade, and traffic speeds are the most significant influencing factors in the formation of corrugation.