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Author: Raul Avelar Publisher: ISBN: Category : Speed limits Languages : en Pages : 52
Book Description
The objective of this study was to perform rigorous safety effectiveness evaluations of variable speed limit (VSL) implementation on freeway corridors. To accomplish this objective, the research team compiled safety data from Virginia, Wyoming, and Georgia and used an interrupted time series study design (with a comparison group for Georgia). The team analyzed data using logistic and negative binomial generalized estimating equations models. The results from Wyoming and Georgia produced evidence of significant reductions in several types of crashes. The research team found total crash reductions of 34.4 and 29.2 percent associated with VSL installations in Wyoming and Georgia, respectively. The economic evaluation for these two States generally indicated larger benefits than costs. For Georgia, the estimated benefit–cost (B/C) ratio was 40.38. The economic analysis for Wyoming yielded a more modest B/C ratio of 9.05, though still indicating benefits outweighing VSL installation costs. Results from Virginia were inconclusive as the analysis found no statistical evidence of a change in overall safety. The inconclusiveness of these results is possibly due to the sample size of the after period, the small amount of time the system was active, and the manner in which the VSL was used in the corridor for enhancing safety during adverse weather conditions.
Author: Raul Avelar Publisher: ISBN: Category : Speed limits Languages : en Pages : 52
Book Description
The objective of this study was to perform rigorous safety effectiveness evaluations of variable speed limit (VSL) implementation on freeway corridors. To accomplish this objective, the research team compiled safety data from Virginia, Wyoming, and Georgia and used an interrupted time series study design (with a comparison group for Georgia). The team analyzed data using logistic and negative binomial generalized estimating equations models. The results from Wyoming and Georgia produced evidence of significant reductions in several types of crashes. The research team found total crash reductions of 34.4 and 29.2 percent associated with VSL installations in Wyoming and Georgia, respectively. The economic evaluation for these two States generally indicated larger benefits than costs. For Georgia, the estimated benefit–cost (B/C) ratio was 40.38. The economic analysis for Wyoming yielded a more modest B/C ratio of 9.05, though still indicating benefits outweighing VSL installation costs. Results from Virginia were inconclusive as the analysis found no statistical evidence of a change in overall safety. The inconclusiveness of these results is possibly due to the sample size of the after period, the small amount of time the system was active, and the manner in which the VSL was used in the corridor for enhancing safety during adverse weather conditions.
Author: Publisher: ISBN: Category : Speed limits Languages : en Pages : 0
Book Description
This document is a technical summary of the Federal Highway Administration Report Developing Crash Modification Factors for Variable Speed Limits (FHWA-HRT-21-053) (Avelar et al. 2021).
Author: David L. Harkey Publisher: Transportation Research Board ISBN: 0309117380 Category : Transportation Languages : en Pages : 85
Book Description
TRB¿s National Cooperative Highway Research Program (NCHRP) Report 617: Accident Modification Factors for Traffic Engineering and ITS Improvements explores the development of accident modification factors (AMFs) for traffic engineering and intelligent transportation system improvements. AMFs, also known as crash reduction factors, are designed to provide a simple and quick way of estimating the safety impacts of various types of engineering improvements, encompassing the areas of signing, alignment, channelization, and other traffic engineering solutions.
Author: Abdulla Ali Publisher: ISBN: Category : Traffic accident investigation Languages : en Pages : 306
Book Description
Vehicle crashes on roadways are one of the most challenging problems affecting many parts of the world. Michigan, having freeways that progressively get busier each year, has also seen an increase in vehicle crashes. These crashes are due to several factors including human errors, roadway deficiencies, environmental factors, vehicle factors, etc. A study conducted by Michigan Traffic Crash Facts (MTCF) estimates a crash will happen every 44 minutes and a person will die every six hours on Michigan roadways. The success of traffic safety and highway improvement programs depends on the analysis of accurate and reliable vehicle crash data. This study intended to find the effect of the speed limit and road and weather conditions on the frequency of crashes in the investigated black spots and the effect of using the driving simulator to establish crash modification factor on decreasing the number of crashes. This study discusses the traffic information on 18 freeways in the State of Michigan in the years 2010-2014. High crash rate locations (black spots) and safety deficient areas on the highways were identified by using Geographic Information System (GIS) software. Two statistical black spot identification techniques, Kernel Density Estimation (KDE) and Point Density Estimation (PDE), were used. By comparing the two methods, our research found that KDE is more capable of pinpointing black spots than the PDE method. The KDE study revealed a black spot on a section of I-69 in Flint, Michigan. From this data, ten different driving simulator scenarios were developed with the same roadway track. To better understand driver behavior and responses, different road and weather conditions were incorporated. By using an Internet Scene Assembler (ISA) and SimCreator, making various changes to the driving tests were simplified. Using a multi-user driver simulator environment, different contributing factors for crashes were created and countermeasures were tested. One hundred subjects (81 males and 19 females) were recruited from the Lawrence Technological University (LTU) community to participate in this driver simulator study. Resulting data were analyzed. From this analysis, a predictive model that focused on driving behavior was developed and based on easily interpretable variables. The categories of the independent variable (speed limit, speeding, brake respond) were considered nominal. To determine the possible factors contributing to a crash type, the multinomial logistic regression model (MNL) was fitted to the set of available independent variables. After developing the MNL model fitted with data explanatory variables, certain crash types were observed as being statistically significant. Speeding and speed limit during certain inclement road/weather conditions had the greatest effect on crashes. The subjectivity of the driver’s perception of the safety and effectiveness of countermeasures were considered using fuzzy mathematics. The driver data were used as input into a fuzzy model using the fuzzy rule base. A safety level was compared to speed limits to determine if the proposed speed limit contributed to a risky or safe situation. The fuzzy model showed that in snowy and icy weather conditions the speed limit has to be reduced from 70 mph by 10-20 mph. In this study, the Crash Modification Factors (CMF) for selected countermeasures were estimated using the driver simulator scenarios. The expected CMF gives the notion of whether a treatment or a change in the speed limit in certain weather conditions will lead to change in the number of crashes and consequently a change in the safety level. The results concluded that most frequent crashes occur during snowy and icy weather conditions and by changing the speed limit during these weather conditions, the number of road crashes can be reduced. These crash reductions can be shown as CMFs. The method of developing CMFs used in this study is considered a new dimension that will increase road safety and reduce the rate of road traffic crashes. Keywords: Kernel Density Estimation (KDE) and Point Density Estimation (PDE), logistic regression model, fuzzy mathematics, Crash Modification Factors (CMF).
Author: Eugene Vida Maina Publisher: ISBN: Category : Languages : en Pages : 120
Book Description
Studies have shown that, roadway safety has become an intensively investigated topic with the objective of improved understanding of the factors that cause crashes to occur. However, it has been shown that as traffic volumes continue to increase across the United States, 52% of drivers feel less safe on the roads today more than they did five years ago and that the American public feels that traffic safety is a serious problem that needs both the government and media to pay more attention to this issue. In response to these public and driver grievances, State and National transportation agencies have been and continue to pursue and understand the causes and solutions that would significantly reduce roadway crash frequencies. At national level, through various and rigorous studies, the American Association of State Highway and Transportation Officials, AASHTO has published the Highway Safety Manual to quantify safety using predictive models and CMFs. Various efforts have been attempted at state level too, for example, Texas DOT has developed an Interim Roadway Safety Design Workbook that describes the relationship between various roadway elements and each element influences roadway safety. In an effort to contribute towards understanding and resolving the factors that influence crash frequencies on roadways, through a thorough literature search. This study realizes that although there has been vast research in this area, no study has explicitly explained why there is variation in crash frequencies on roadways segments with similar physical/geometric features and annual average daily traffic (AADT). Studies suggest that these variations are due to volume changes throughout the day, an effect literature shows that can only be addressed by hourly volumes and not AADT. Driven by these literature conclusions, this dissertation develops crash modification factors (CMFs) for urban freeways by considering level of service (LOS) deterioration due to change in hourly traffic volumes. Here, this study investigates LOS when it deteriorated from A to B, B to C, C to D, D to E and E to F using hourly volume and hourly crash data collected on urban freeway segments, specifically routes US 1, NJ 3 and NJ 21 in the State of New Jersey. Data were collected on 14 miles of urban freeway segments and 1344 hours of traffic volume count and crash data were analyzed for a period of four years, 2008, 2009, 2010, and 2011. Results from this investigation, shows that operational elements have some influence on urban freeway safety. This dissertation shows that as LOS deteriorated from A to B, B to C, C to D, D to E and E to F, the estimated CMFs were 0.673, 1.110, 0.865, 1.452, and 0.370 respectively. These findings concur with those referred to in this dissertation’s literature review findings, which showed that by adding capacity, that is, by reducing congestion initially results in safety improvement that diminishes as congestion increases.
Author: Daniel Lance Carter Publisher: ISBN: 9780309686860 Category : Roads Languages : en Pages : 0
Book Description
Crash modification factors (CMF) provide transportation professionals with the kind of quantitative information they need to make decisions on where best to invest limited safety funds.
Author: Raul Avelar
Author: Raul Avelar
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Author: Frank Gross
Author: David L. Harkey
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Author: David K. Merritt
Author: Abdulla Ali
Author: Eugene Vida Maina
Author: Daniel Lance Carter