Wu X.,500 Pillsbury Drive S.E. |
Liu H.X.,500 Pillsbury Drive S.E. |
Gettman D.,Kimley Horn and Associates Inc.
Transportation Research Part C: Emerging Technologies | Year: 2010
Conceptually, an oversaturated traffic intersection is defined as one where traffic demand exceeds the capacity. Such a definition, however, cannot be applied directly to identify oversaturated intersections because measuring traffic demand under congested conditions is not an easy task, particularly with fixed-location sensors. In this paper, we circumvent this issue by quantifying the detrimental effects of oversaturation on signal operations, both temporally and spatially. The detrimental effect is characterized temporally by a residual queue at the end of a cycle, which will require a portion of green time in the next cycle; or spatially by a spill-over from downstream traffic whereby usable green time is reduced because of the downstream blockage. The oversaturation severity index (OSI), in either the temporal dimension (T-OSI) or the spatial dimension (S-OSI) can then be measured using high-resolution traffic signal data by calculating the ratio between the unusable green time due to detrimental effects and the total available green time in a cycle. To quantify the T-OSI, in this paper, we adopt a shockwave-based queue estimation algorithm to estimate the residual queue length. S-OSI can be identified by a phenomenon denoted as " Queue-Over-Detector (QOD)" , which is the condition when high occupancy on a detector is caused by downstream congestion. We believe that the persistence duration and the spatial extent with OSI greater than zero provide an important indicator for measuring traffic network performance so that corresponding congestion mitigation strategies can be prepared. The proposed algorithms for identifying oversaturated intersections and quantifying the oversaturation severity index have been field-tested using traffic signal data from a major arterial in the Twin Cities of Minnesota. © 2010 Elsevier Ltd.
Gartner A.,Kimley Horn and Associates Inc. |
Douglas E.P.,University of Florida |
Dolan C.W.,University of Wyoming |
Hamilton H.R.,University of Florida
Journal of Composites for Construction | Year: 2011
This paper presents the development of a test method that can be used to test the bond capacity of carbon fiber-reinforced polymer (CFRP) composites bonded to concrete. The rationale for the selection of the test method is described along with the results of the experimental work used to refine the test configuration and procedures. The research objectives were to develop a test method that (1) can be used to evaluate the durability of the FRP-concrete bond (adhesion failure mode); (2) facilitate multiple replicate for statistical validation; (3) is simple to conduct; and (4) provides comparative results that are easy to interpret. The method utilizes a small concrete beam modeled after the modulus of rupture test, which is typically used to measure concrete tensile strength. A number of small beam sizes and loading configurations were considered during the investigation. The final recommended specimen configuration is 4×4×14 in. (100 mm×100 mm×356 mm) beam with a half-depth saw cut at midspan. A 1 in. (25 mm) wide by 8 in. (203 mm) long CFRP strip is applied to the tension face of the beam over the saw cut. The specimen is loaded until failure with a single concentrated load at midspan over a 12 in. (305 mm) span. For durability testing, samples are prepared with the same materials and exposed to the desired accelerated conditioning protocol. Companion unexposed samples are also tested and the relative decrease in capacity is reported as the load to failure of the exposed specimen to that of the control specimen. © 2011 ASCE.
Johnson J.,Kimley Horn and Associates Inc. |
Chowdhury M.,Clemson University |
He Y.,Clemson University |
Taiber J.,Clemson University
Transportation Research Part C: Emerging Technologies | Year: 2013
Due to the tremendous political, economical, and environmental pressures the transportation sector is facing, the United States finds itself devoting more energy to innovative solutions such as electric vehicle (EV) technologies. The purpose of this study was to analyze how utilizing real-time information dissemination transferring capabilities to vehicles, as envisioned in the " connected vehicle" system, could effectively facilitate the EV charging process at fast-charging stations (CS). By simulating a traffic network of EVs in MATLAB, it was found that the total time due to the battery charging process was optimized at both the individual EV and the entire network levels for EVs that were able to use connected vehicle communications. As a result of this optimization, the improvement of two vehicle parameters, extra travel time due to charging and time spent in the CS queue, as well as two CS parameters, queue length and total energy output, were measured. Through connected vehicle technologies, the average extra travel time due to charging and the average time spent in the CS queue were significantly reduced, resulting in benefits at both a network level and individual vehicle level. However, as a tradeoff of the optimization, the charging infrastructure may need to be upgraded in order to increase the capacity of the network. Most importantly, the benefits of connected vehicle systems were found to steadily increase as the market penetration level of EVs also increased in the varying simulation scenarios. © 2012 Elsevier Ltd.
Shields D.J.,Kimley Horn and Associates Inc.
Journal - American Water Works Association | Year: 2012
Previous studies have identified water meter inaccuracy at low flow rates as a significant source of nonrevenue flow for water systems. However, a lack of available data makes it difficult to include low-flow accuracy and accuracy degradation in meter replacement plans. This article examines results from an extensive accuracy program carried out at the Utah Water Research Laboratory on small water meters over a wide range of flow rates and at various levels of throughput. The article compares expected apparent losses of different types of water meters based on a flow profile and expected daily use for the state of California. By including an average composite charging rate, the method developed in this study can determine the meter replacement payback period for different meter types. The analysis contained in this article is intended as a guide to assist utility managers when developing meter replacement plans.
Lott J.S.,Kimley Horn and Associates Inc.
Automated People Movers and Transit Systems 2013: Half a Century of Automated Transit - Past, Present, and Future - Proceedings of the 14th International Conference | Year: 2013
The paper examines the prospect of applying automated transit circulator systems for the "last mile" conveyance of passengers between a high-speed rail station and their destination in the surrounding urban district. The characteristics of high-speed rail stations are discussed with respect to their scale, urban context and ridership demand patterns, and the capacity requirements for automated systems to serve in the "last mile" function. Current project work on the Texas DOT Intercity Passenger Rail Ridership Study is referenced, and a discussion of the simulation and analysis methodologies being used in the study are compared to similar methodologies previously applied to study automated guideway transit connector systems in airports. The paper concludes with an assessment of the suitability of conceptual aerial guideway automated transit systems in conjunction with high speed rail stations for each of the main classifications of automated transit technologies. © 2913 American Society of Civil Engineers.