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Congestion begins when an excess of vehicles on a segment of roadway at a given time, resulting in speeds that are significantly slower than normal or 'free flow' speeds. Congestion often means stop-and-go traffic. The transition ...
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Congestion begins when an excess of vehicles on a segment of roadway at a given time, resulting in speeds that are significantly slower than normal or 'free flow' speeds. Congestion often means stop-and-go traffic. The transition occurs when vehicle density (the number of vehicles per mile in a lane) exceeds a critical level. Once traffic enters a state of congestion, recovery or time to return to a free-flow state is lengthy; and during the recovery process, delay continues to accumulate. The breakdown in speed and flow greatly impedes the efficient operation of the freeway system, resulting in economic, mobility, environmental and safety problems. Freeways are designed to function as access-controlled highways characterized by uninterrupted traffic flow so references to freeway performance relate primarily to the quality of traffic flow or traffic conditions as experienced by users of the freeway.
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As part of this research project, a computer program, SIGTRAN, was developed toestimate the impacts of the transition phase when changing timing plans. The program uses the same procedures as PASSER II-90 to compute the estimated ...
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As part of this research project, a computer program, SIGTRAN, was developed toestimate the impacts of the transition phase when changing timing plans. The program uses the same procedures as PASSER II-90 to compute the estimated delay due to transition. Using the SIGTRAN program, a proposed algorithm for selecting new timing plans in a traffic responsive mode was developed. The algorithm compares the delay associated with retaining the old traffic signal timing to the delay associated the implementing a new timing plan plus the delay caused by transitioning to the new timing plan. If the delay for the old timing plan exceeded the delay estimates for the new timing plan plus the delay accrued during transition, then the new timing plan was adopted; otherwise, the old timing plan was retained. The new algorithm was tested using data from NASA Road 1 in Houston, Texas. It was found that the traffic responsive timing plans developed using the algorithm produced substantial delay savings in the A.M. Peak and Noon periods over operating the signals in a time-of-day mode. Less significant delay savings were generated during the A.M. Off-Peak, P.M. Off-Peak, and P.M. Peak periods. During these periods, either traffic volumes did not change significantly or the differences in the timing plans were so slight that most of the benefits of changing timing plans were offset by the increase in delays caused by transitioning to the new timing plans.
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This report describes the impacts of bottlenecks and interruptions to the flow of goods through the nations major freight corridors and intermodal connectors, the dynamics of that flow in response to disruptions, and the full econ...
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This report describes the impacts of bottlenecks and interruptions to the flow of goods through the nations major freight corridors and intermodal connectors, the dynamics of that flow in response to disruptions, and the full economic impact on public and private entities beyond just the critical infrastructure and the carriers that depend on that flow. The report developed two approaches to analyzing the economic impacts: (1) a high-level methodology (that provides the user with rules of thumb that can be used to estimate the likely economic costs associated with any type of disruption) based on the concept that the economic impact of any disruption would depend primarily on the commodity characteristics, the extent and nature of the disruption, and the costs associated with different elements of the cost structure; and (2) a more detailed methodology that depends on a much higher level of detail and more sophisticated analysis of the supply chain dynamic. This research will help to increase public understanding of the freight transportation system and improve the nations ability to rapidly reconfigure the goods movement system to minimize disruptions.
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This eleventh volume of NCHRP Report 525: Surface Transportation Security will assist transportation, security, and emergency-preparedness planners as they identify and prioritize potential high-value transportation choke points (...
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This eleventh volume of NCHRP Report 525: Surface Transportation Security will assist transportation, security, and emergency-preparedness planners as they identify and prioritize potential high-value transportation choke points (TCPs) such as bridges, tunnels, and passes. These high-value TCPs are located predominantly along major transportation routes. A key area of concern is how disruptive events will affect the flow of commercial traffic through TCPs. The Disruption Impact Estimating Tool-Transportation (DIETT) is an electronic analytical tool that calculates direct transportation and economic impact (costs) of an event that precludes the use of a TCP, and it prioritizes TCPs on the basis of these criteria. DIETT does not calculate replacement costs. Using DIETTs, prioritized sets of outputs, along with other risk information, decision makers will be able to better focus their capital resource, security, and emergency-preparedness planning.
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Chapter 10 of the FDOT Plans Preparation Manual titled 'Work Zone Traffic Control' contains a lane closure analysis procedure, in which a 'Remaining Traffic Factor' (RTF) is used to account for possible traffic diversion during a ...
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Chapter 10 of the FDOT Plans Preparation Manual titled 'Work Zone Traffic Control' contains a lane closure analysis procedure, in which a 'Remaining Traffic Factor' (RTF) is used to account for possible traffic diversion during a lane closure. However, no guidance has been offered on how to obtain the value of the RTF. The purposes of the study are twofold. First, diversion behaviors at work zones were modeled in a discrete choice modeling framework. The authors conducted a stated preference survey to collect data on drivers' diversion propensity and then calibrated a binary logit model. The model provides a better understanding of drivers' diversion behaviors at work zones, and can be used to forecast diversion rates in a work zone traffic analysis. Second, they proposed two procedures, namely open-loop and closed-loop, to apply the calibrated binary logit model to computer the RTF. An Excel tool was developed to facilitate the computation.
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An important motivation for transportation investment in many urban areas is toaddress increasing traffic congestion. This has led local and state transportation officials, including the American Association of State Highway and T...
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An important motivation for transportation investment in many urban areas is toaddress increasing traffic congestion. This has led local and state transportation officials, including the American Association of State Highway and Transportation Officials (AASHTO), to be concerned about how increasing congestion can affect economic growth. Past attempts to assess the economic implications of congestion have found that this is a difficult relationship to document. The most obvious approach, asking businesses in congested areas how they are affected, is problematic because those that have been driven out of business or driven away because of congestion are no longer present, and the remaining businesses typically are unable to report how different their operations would be under a hypothetical scenario of no congestion. As a result, this study has been designed to assess the economic implications of congestion by using an empirical analysis approach, which documents the many aspects of congestion-related costs incurred by different types of business operations in different types of urban settings; statistical analysis is then used to show how transportation costs have affected patterns of businesses in two major metropolitan areas.
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The traffic investigation is one of the most important parts of an Environmental Impact Statement of projects involving the construction of new roadway facilities and/or the improvement of existing ones. The focus of the traffic a...
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The traffic investigation is one of the most important parts of an Environmental Impact Statement of projects involving the construction of new roadway facilities and/or the improvement of existing ones. The focus of the traffic analysis is on the determi
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Traffic congestion has numerous negative effects on the movement of people and goods, economic productivity and the environment. These effects include increased travel times resulting in lost wages and decreased labor productivity...
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Traffic congestion has numerous negative effects on the movement of people and goods, economic productivity and the environment. These effects include increased travel times resulting in lost wages and decreased labor productivity, wasted fuel and cost associated with it, deteriorating air quality, and drivers stress, which can adversely affect safety, health, and labor productivity. In recent years these effects have come to the forefront of the publics concern. In order to quantify traffic congestion and its impacts on New Jerseys motorists, New Jersey Institute of Technology (NJIT) developed the Congestion Analysis Model. This is a computer software tool that estimates congestion costs, congestion related travel delay, and mobility indicators for New Jersey highways. The key advantage of NJITs model over other computer models developed for the same purpose is that it uses the New Jersey Congestion Management System (NJCMS) database to calculate travel delays and other congestion indicators. This project builds on the accomplishments of the previous work on developing congestion analysis software. Specific objectives of this project are to update the calculation methodology, improve softwares user interface, redesign the output tables to meet NJDOTs requirements, update software documentation, and provide limited technical support to NJDOT users.
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Incident detection systems have the potential of reducing the time between the211 occurrence of accidents and the notification of emergency medical services, 211 called the accident notification time. Reductions in this time, in t...
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Incident detection systems have the potential of reducing the time between the211 occurrence of accidents and the notification of emergency medical services, 211 called the accident notification time. Reductions in this time, in turn, may 211 affect the numbers of fatalities. A statistical analysis is conducted to 211 determine the quantitative relationship between fatalities and the accident 211 notification time on urban freeways. Using this relationship, the impact of 211 freeway incident detection systems on fatalities is estimated. are also derived. 211 The economic benefits of fatality reduction are also derived.
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