The main objective of this study is to evaluate the effectiveness of using active traffic management (ATM) strategies on freeways in terms of the driver's behavior and operational impacts. A few test beds were selected to evaluate the impacts of ATM such as speed harmonization, shoulder utilization, and ramp metering. Test beds used in this study were at places where an ATM is either proposed or previously implemented, i.e., where data exists for conditions prior to and after the implementation of ATM. Data collected from the test beds were used in a simulation model to evaluate the impacts of each ATM strategy on speed, travel time, and crash rates. Simulation results indicated that the implementation of speed harmonization on US 90 showed a 14% reduction in crashes and a 2%-3% increase in freeway speed; the implementation of hard shoulders on US 90 showed a 39% increase in travel time, 22% increase in freeway capacity and 60% decrease in delays; and the implementation of ramp metering on US 59 between Bissonnet St. and Fondern road showed a decrease of 23 % in freeway travel time, a 14% increase in freeway speed and 11% decrease in accident rates.
This article presents the state-of-the-art literature review for the behavior of fiber-reinforced polymer and performance of fiber-reinforced polymer reinforced concrete structures exposed to high temperatures. The article is organized into six parts. They are thermo-mechanical properties of fiber-reinforced polymer composites, bond characteristics of fiberreinforced polymers at high temperatures, fire reaction properties of fiber-reinforced polymer composites, fire protection methods, performance of fiber-reinforced polymer reinforced concrete structures under fire conditions, and design codes. The design codes presented herein are that of American Concrete Institute and the Canada Standards Association. Sections pertaining to fiber-reinforced polymer fire design in these codes are discussed, including the future developments for enhancing the performance of fiber-reinforced polymer reinforced concrete structures under elevated temperatures.
Four barrier wall materials (cement-asphalt emulsion, bentonite clay-sand, organophilic clay-cement, and attapulgite clay-cement) were evaluated to determine which would have low hydraulic conductivity to water and the ability to maintain that low hydraulic conductivity (less than 1 x 10"7 cm/s) when permeated by a dense nonaqueous-phase liquid (DNAPL). A full-strength DNAPL, méthylène chloride, was used to simulate the worst-case scenario of permeation of a barrier wall by a DNAPL.Cement-asphalt emulsion (Aspemix) and bentonite clay-sand were found to be incompatible with the DNAPL used because large hydraulic conductivity increases occurred when the material was permeated by the DNAPL. Organophilic clay-cement and attapulgite clay-cement (Impermix) were compatible with the DNAPL, because there was little to no change in hydraulic conductivity after permeation by the DNAPL. The organophilic clay-cement, however, had hydraulic conductivity values that were higher than 1 x 10"7 cm/s to both water and DNAPL. Attapulgite clay-cement had low conductivity values to both water and DNAPL.
This paper introduced an optimization model to address dynamic speed control strategies for achieving network-wide speed harmonization. Genetic Algorithm (GA) was applied to search the optimal solution of the proposed model. During the search process, a computational fluid dynamics (CFD) based analytical model and microscopic traffic simulation VISSIM were applied to evaluate the performance of possible solutions. The proposed model can be used to determine the deployment of dynamic speed limits, the displayed speed limit, and the timing to change these speed limits. The proposed model was tested using VISSIM in an urban freeway network of about 12 miles long. Different simulation scenarios with varying AADT from 60,000 to 12,000 were tested. It was found that when properly implemented, dynamic speed control can improve traffic flow conditions, reduce congestion and emission, and enhance network throughput. For example, in the selected urban freeway network with the AADT of 80,000, the proposed dynamic speed control strategy can save 5% average travel time, reduce 9% of the vehicles with high collision risk and about 11% emission.
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