A Simulation Based Approach To Evaluate Safety Impacts Of Increased Traffic Signal Density
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A Simulation Based Approach To Evaluate Safety Impacts Of Increased Traffic Signal Density
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Author : Kenneth P. Drummond
language : en
Publisher:
Release Date : 2002
A Simulation Based Approach To Evaluate Safety Impacts Of Increased Traffic Signal Density written by Kenneth P. Drummond and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Roads categories.
One of the most controversial access management techniques practitioners face is also one of the most common: restricting signal density. Increased signal density can improve access for minor approaches to a corridor; however, it can also increase delays and rear-end crashes for vehicles on the mainline (major) approach. An ability to evaluate the impacts of increased signal spacing is thus critical for decision makers. Because crash data are not always easy to obtain, a logical question arises: Can simulation models be used to evaluate the safety impacts of increased traffic signal density? This report describes a method for using simulation models to evaluate the safety impacts of increased traffic signal density in suburban corridors. Using 10 years of data from two major arterials in Virginia, actual crash rates were compared with operational performance measures simulated by the Synchro/SimTraffic model. As expected, crash rates were positively correlated with stops per vehicle and delay per vehicle and negatively correlated with mainline speed. Three findings were significant. First, the correlation between crash rates and select mainline performance measures (delay, speed, and stops) was relatively strong despite the inherent variability in crash rates: R2, a measure of explained variance in crash rates, yielded values from 0.54 to 0.89. Second, three distinct regimes relate stops per vehicle to signal density: the installation of the first few signals causes a drastic increase in stops, the addition of the next set of signals causes a moderate increase in stops, and the addition of a third set of signals does not significantly affect the number of stops per vehicle. Third, multiple regime models also relate delay per vehicle to signal density. This study recommends two practical applications. To the extent these mainline performance measures correlate with crashes, simulation modeling may be used to estimate safety impacts of increased signals, which is appealing because simulation packages are becoming easier to apply. Further, three regime models can suggest when, in the timeline of corridor development, the addition of a traffic signal is likely to degrade corridor performance significantly versus when it will have little effect, thereby allowing decision makers to expend political capital when it is most beneficial (e.g., the occasions when there is significant degradation of corridor performance). Most important, the approach herein suggests a long-range corridor-planning tool for evaluating the impacts of different access densities.
Traffic Signal Retiming Practices In The United States
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Author : Robert L. Gordon
language : en
Publisher: Transportation Research Board
Release Date : 2010
Traffic Signal Retiming Practices In The United States written by Robert L. Gordon and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Technology & Engineering categories.
TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 409: Traffic Signal Retiming Practices in the United States explores practices that operating agencies currently use to revise traffic signal timing. The report examines the processes used to develop, install, verify, fine-tune, and evaluate the plans--
Simulation Based Evaluation Of Traffic Safety Performance Using Surrogate Safety Measures
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Author : Hong Yang
language : en
Publisher:
Release Date : 2012
Simulation Based Evaluation Of Traffic Safety Performance Using Surrogate Safety Measures written by Hong Yang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Traffic safety categories.
Traffic safety evaluation is one of the most important processes in the analysis of transportation systems performance. The use of traditional crash-data-oriented methodologies to analyze traffic safety problems has been frequently questioned due to shortcomings such as unavailability and low quality of historical crash data. The advancement of traffic conflict techniques and micro-simulation tools motivated this dissertation to develop a simulation-based approach of combining micro-simulation models and traffic conflict technique to investigate the safety issues in traffic systems. The proposed simulation-based approach consists of two major components: the development of surrogate safety measures; and the integration of the developed surrogate safety measures with micro-simulation models. In this dissertation, a new surrogate safety measure is derived and applied in micro-simulation models to capture the conflict risk of the interactions among vehicles. The conceptual and computational logics of the proposed surrogate safety indicator are described in detail. A calibration procedure that focuses on safety evaluation using the simulation model with the new surrogate measure has been proposed. The proposed calibration approach has been developed based on the stochastic gradient approximation algorithms to find optimal parameters of the stochastic traffic simulation models. The calibration methodology has been implemented on a selected traffic simulation platform to test its performance. Simulated operational measurements and traffic conflict risk in terms of the surrogate safety measure are quantified and compared with observations derived from high resolution vehicle trajectory data. The calibrated traffic model has also been validated by using independent vehicle trajectory data saved as a hold-out sample. The results show that the fine-tuning of parameters using the proposed calibration approach can significantly improve the performance of the simulation model to describe actual traffic conflict risk as well as operational performance. The applicability of the proposed new surrogate measure and the simulation-based safety evaluation approach using this surrogate measure has been successfully demonstrated through several cases studies. The overall findings can inform road safety investigators as to how operations-oriented simulation models in conjunction with the surrogate safety measure can complement traffic safety evaluation in cases to which traditional approaches are not applicable.
Identifying And Quantifying Operational And Safety Performance Measures For Access Management
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Author : William L. Eisele
language : en
Publisher:
Release Date : 2005
Identifying And Quantifying Operational And Safety Performance Measures For Access Management written by William L. Eisele and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Traffic congestion categories.
Fundamentals Of Traffic Simulation
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Author : Jaume Barceló
language : en
Publisher: Springer Science & Business Media
Release Date : 2011-01-06
Fundamentals Of Traffic Simulation written by Jaume Barceló and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-01-06 with Business & Economics categories.
The increasing power of computer technologies, the evolution of software en- neering and the advent of the intelligent transport systems has prompted traf c simulation to become one of the most used approaches for traf c analysis in s- port of the design and evaluation of traf c systems. The ability of traf c simulation to emulate the time variability of traf c phenomena makes it a unique tool for capturing the complexity of traf c systems. In recent years, traf c simulation – and namely microscopic traf c simulation – has moved from the academic to the professional world. A wide variety of traf- c simulation software is currently available on the market and it is utilized by thousands of users, consultants, researchers and public agencies. Microscopic traf c simulation based on the emulation of traf c ows from the dynamics of individual vehicles is becoming one the most attractive approaches. However, traf c simulation still lacks a uni ed treatment. Dozens of papers on theory and applications are published in scienti c journals every year. A search of simulation-related papers and workshops through the proceedings of the last annual TRB meetings would support this assertion, as would a review of the minutes from speci cally dedicated meetings such as the International Symposiums on Traf c Simulation (Yokohama, 2002; Lausanne, 2006; Brisbane, 2008) or the International Workshops on Traf c Modeling and Simulation (Tucson, 2001; Barcelona, 2003; Sedona, 2005; Graz 2008). Yet, the only comprehensive treatment of the subject to be found so far is in the user’s manuals of various software products.
Speed Management
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Author : European Conference of Ministers of Transport
language : en
Publisher: OECD Publishing
Release Date : 2006-10-13
Speed Management written by European Conference of Ministers of Transport and has been published by OECD Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006-10-13 with categories.
Speeding is the number one road safety problem in a large number of OECD/ECMT countries. It is responsible for around one third of the current, unacceptably high levels of road fatalities. Speeding has an impact not only on accidents but also on the ...
Computer Modeling And Simulation Of New Jersey Signalized Highways
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Author : I-Jy Steven Chien
language : en
Publisher:
Release Date : 2005
Computer Modeling And Simulation Of New Jersey Signalized Highways written by I-Jy Steven Chien and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Electronic traffic controls categories.
Integrating Observational And Microscopic Simulation Models For Traffic Safety Analysis
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Author : Usama Elrawy Shahdah
language : en
Publisher:
Release Date : 2014
Integrating Observational And Microscopic Simulation Models For Traffic Safety Analysis written by Usama Elrawy Shahdah and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
In safety analysis, two questions typically need to be addressed: 1) how to identify unsafe sites for priority intervention? and 2) how to determine the effectiveness of treatments introduced at these and other sites? Two types of approaches have been considered in the literature to provide answers for these questions: (1) observational models based on historical crash data and (2) observed or simulated higher risk vehicle interactions or traffic conflicts. Observational crash-based models are good at predicting higher severity crashes, but they tend to ignore higher risk vehicle interactions that compromise safety, that have not resulted in crashes (e.g. near misses). Proponents of microscopic simulation argue that ignoring these higher risk interactions can severely understate the safety problem at a given site and lead to a misallocation of scarce treatment funds. Another problem with observational crash prediction models is the need for sufficient crash data reported over an extended period of time to provide reliable estimates of “potential” lack of safety. This requirement can be a challenge for certain types of treatment and different sites or locations. Furthermore, observational approaches are not causal in nature, and as such, they fail to provide a sound “behavioural” rationale for “why” certain treatments affect safety. On the other hand, traffic conflicts occur more frequently than crashes and can provide a stronger experimental basis for estimating safety effects on a short-term basis. This is especially important given the rare random nature of crashes for certain traffic conditions. Additionally, they provide a more rational basis for lack of safety than is normally available from crash occurrence data. Basically, through the application of calibrated behavioural simulation, traffic conflicts can be linked to specific driver actions and responses at a given site, more so than conventional reported crashes. As such, they permit a causal underpinning for possible treatment effects and this is important to decision-makers because it underscores why certain treatments act to enhance safety, rather than simply providing an estimate of the treatment effect itself. Notwithstanding the usefulness of conflict-based measures, observed crashes remain the primary verifiable measure for representing failures in the transportation systems. Unfortunately traffic conflicts have not been formally linked to observed crashes, and hence their values as indicators for treatment effect have not been fully explored. This presents a challenge on how best to use both conflicts and observed crashes to better understand where safety is most problematic, where intervention is needed, and how best to resolve specific safety problems? In this thesis, the position is taken that a complete understanding of safety problems at a given site can only emerge from a more inclusive analysis of both observed crashes and traffic conflicts. This is explored by developing two integrated models: (1) An integrated priority ranking model is presented that combines estimates from observational crash prediction with an analysis of simulated traffic conflicts; (2) An integrated treatment model is presented that uses simulated traffic conflicts that are linked statistically to observed crashes to provide estimates of crash modification factor (CMF). The suitability of these integrated models has been evaluated using data for a sample of signalized intersections from Toronto for the period 1999-2006. In the absence of a benchmark (or true) priority ranking outcome, a number of evaluation criteria were considered, and the integrated ranking model was found to yield better results than both conventional observational crash-based models (including empirical Bayesian, potential for safety improvement methods) and conflict-based models (including conflict frequency and rate for different risk thresholds). For treatment effects, the results suggest that CMFs can be estimated reliably from conflicts derived from microsimulation, where the simulation platform has been sufficiently calibrated. The link between crashes and conflicts provides additional inferences concerning treatment effects, in those cases where treatments were not previously implemented (i.e., no after history). Since there is an absence of crash history, the treatment effect is based exclusively on simulated conflicts. Moreover, the integrated model has the added advantage of providing site-specific CMFs instead of applying a constant CMF across all sites considered for a potential treatment.
Multi Modal Traffic Signal Design Under Safety And Operations Constraints
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Author : Behzad Rouhieh
language : en
Publisher:
Release Date : 2010
Multi Modal Traffic Signal Design Under Safety And Operations Constraints written by Behzad Rouhieh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Currently, most transportation agencies design signal timing plans for intersection with the main objective of minimizing vehicular traffic delay while ensuring compliance with basic safety guidelines. Often times along urban roadways where automobiles share the space with large volumes of non-motorized users (i.e. pedestrians and cyclists), reaching a balance between delays and safety of all road users is a challenging task. In this thesis, different approaches are presented to address potential improvements on traffic operations and. safety of intersections serving more than one mode of transportation. The impact of tunnels on the pedestrian operations and the effect of applying different signal timing plans on the performance of an isolated intersection are being studied. A methodology is proposed to reach a desired compromise between the safety and efficiency of either an isolated intersection or a corridor of independent/coordinated intersections. An integrated delay-safety (DS) indicator is used in combination with a neural network based tool. The proposed methodology was applied to a real-world urban arterial in downtown Montreal, along which a bicycle path was recently built. The study area was evaluated using VISSIM, a microscopic traffic simulator, by coding traffic signal timing plans along the arterial to perform independently, or coordinated. The objective is to advance with minimum delay a specified transportation mode (i.e. automobiles or bicycles). A Multi-Layer Perceptron (MLP) neural-network was built to identify what type of signal timing plan yields the best tradeoff between automobile delay and safety of non-motorized users. Based on traffic data collected from real-world and from simulations, a large date set of input/output pairs was used to train and test the MLP neural network. It was found that for 99.8% of the tested cases the neural network identifies correctly the configuration of signal timing plan that yields the optimal DS value.
Traffic Engineering Handbook
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Author : ITE (Institute of Transportation Engineers)
language : en
Publisher: John Wiley & Sons
Release Date : 2016-01-19
Traffic Engineering Handbook written by ITE (Institute of Transportation Engineers) and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-01-19 with Technology & Engineering categories.
Get a complete look into modern traffic engineering solutions Traffic Engineering Handbook, Seventh Edition is a newly revised text that builds upon the reputation as the go-to source of essential traffic engineering solutions that this book has maintained for the past 70 years. The updated content reflects changes in key industry standards, and shines a spotlight on the needs of all users, the design of context-sensitive roadways, and the development of more sustainable transportation solutions. Additionally, this resource features a new organizational structure that promotes a more functionally-driven, multimodal approach to planning, designing, and implementing transportation solutions. A branch of civil engineering, traffic engineering concerns the safe and efficient movement of people and goods along roadways. Traffic flow, road geometry, sidewalks, crosswalks, cycle facilities, shared lane markings, traffic signs, traffic lights, and more—all of these elements must be considered when designing public and private sector transportation solutions. Explore the fundamental concepts of traffic engineering as they relate to operation, design, and management Access updated content that reflects changes in key industry-leading resources, such as the Highway Capacity Manual (HCM), Manual on Uniform Traffic Control Devices (MUTCD), AASSHTO Policy on Geometric Design, Highway Safety Manual (HSM), and Americans with Disabilities Act Understand the current state of the traffic engineering field Leverage revised information that homes in on the key topics most relevant to traffic engineering in today's world, such as context-sensitive roadways and sustainable transportation solutions Traffic Engineering Handbook, Seventh Edition is an essential text for public and private sector transportation practitioners, transportation decision makers, public officials, and even upper-level undergraduate and graduate students who are studying transportation engineering.