Effects Of Geometric Characteristics Of Rural Two Lane Roads On Safety
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Effects Of Geometric Characteristics Of Rural Two Lane Roads On Safety
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Author : Samuel Labi
language : en
Publisher:
Release Date : 2006-06-15
Effects Of Geometric Characteristics Of Rural Two Lane Roads On Safety written by Samuel Labi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006-06-15 with categories.
Applying Safety And Operational Effects Of Highway Design Features To Two Lane Rural Highways
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Author :
language : en
Publisher:
Release Date : 2003
Applying Safety And Operational Effects Of Highway Design Features To Two Lane Rural Highways written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Rural two-lane highways constitute a majority of the mileage of public roads in the United States. Rural two-lane highways have 40% of the total travel but experience 60% of the highway fatalities. During the 1980's and 1990's, research was carried out in the United States to quantify the safety and operational effects of various key geometric design features including: lane and shoulder widths; roadside safety; horizontal and vertical alignment; sight distance; rural intersections. Aggregating this research has resulted in a compendium of the safety benefits of certain geometric design features for two-lane rural highways which links design standards and safety. This aggregated research information provides a basis for software analysis of proposed highway designs to assess their expected safety performance as well as the traditional capacity performance. Application of these benefits and effects achieves a numerical methodology for safety in a similar manner as is commonly carried out for capacity. This compendium of the safety and operational benefits of highway design features is being deployed in the United States to state highway departments in advance of the release of the software based analysis system. For the covering abstract of this conference see ITRD number E211395.
Safety Effects Of Cross Section Design On Rural Multilane Highways
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Author :
language : en
Publisher:
Release Date : 1997
Safety Effects Of Cross Section Design On Rural Multilane Highways written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with Rural roads categories.
National statistics indicate that fatality rates on rural Federal-aid primary highways have been significantly higher compared to those for urban and rural Interstate highways and urban primary highways. Although this group of highways includes two-lane rural roads, an important component of the rural Federal-aid primary highways are multilane rural highways. More than 56 000 km of arterial highways in the United States are multilane, non-Interstate roads in rural areas. Many previous studies have been conducted regarding the safety effects of various traffic and geometric roadway features. The majority of these studies were concentrated on rural two-lane roads. There have also been a few notable studies that investigated roadway crosssection design elements for suburban highways and urban streets. However, there has been limited research on the safety effects of geometric design features on rural, multilane, nonfreeway highways. This study examined the effects of various cross-section-related design elements on accident frequency and developed an accident prediction model for rural, multilane, nonfreeway highways.
Geometric Design Consistency On High Speed Rural Two Lane Roadways
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Author : National Cooperative Highway Research Program
language : en
Publisher: Transportation Research Board
Release Date : 2003
Geometric Design Consistency On High Speed Rural Two Lane Roadways written by National Cooperative Highway Research Program 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 2003 with Express highways categories.
Safety Effects Of Geometric Improvements On Horizontal Curves
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Author : Charles V. Zegeer
language : en
Publisher:
Release Date : 1991
Safety Effects Of Geometric Improvements On Horizontal Curves written by Charles V. Zegeer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with Highway engineering categories.
Horizontal curves represent a considerable safety problem on rural two-lane highways. Curves experience a higher accident rate than tangents. Current road improvements highlight the issue of what else should be done at horizontal curves to enhance (or at least hold constant) the level of safety at these sites. There has been a need to better quantify accident effects of curve features and to quantify the effects on accidents of curve flattening, curve widening, addition of spiral transitions, improvement to deficient superelevation, and improvements to the roadside. The purpose of this research was to determine the horizontal curve features which affect accident experience on two lane rural roads and, also, to determine which types of geometric improvements on curves will affect accident experience and to what extent.
Safety Performance Of Rural Intersections With Atypical Design Characteristics
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Author : Anthony Ingle
language : en
Publisher:
Release Date : 2022
Safety Performance Of Rural Intersections With Atypical Design Characteristics written by Anthony Ingle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Electronic dissertations categories.
The results described in this dissertation represent a culmination of the efforts in the study of safety performance at rural intersections with atypical design characteristics. The specificity of this topic does not limit its relevance to intersection safety and the science of relating infrastructure traits to failure risks. Statistical modelling is used to predict average crash frequency. The model specification uses attributes such as the average annual daily traffic (AADT) on the major and minor road approaches, among other characteristics, to account for the exposure to crashes of various defined types and severities.The atypical intersection geometries studied herein consist of offset-T, curved corner, highly skewed, and multi-leg with five or more intersection legs. All of the intersections studied are minor road stop-controlled, along two-lane two-way rural highways. An effort is made to summarize the outcomes in practically applicable terminology such as Crash Modification Factors (CMFs) so that the conclusions of this study can lend toward a safer transportation future.The investigation into offset-T intersections utilizes a series of random intercept negative binomial models for crash occurrence that was generated based on 10 years of crash data from a sample of 299 offset-T intersections and 301 four-leg intersections with minor stop-control along rural two-lane highways in Michigan. The search for candidate intersections was exhaustive, considering that both major and minor road AADT was desired for each site. The modeling technique used a random effect for each site (location). Models were developed for total (non-animal) intersection crashes, as well as for single motor vehicle, angle, and rear-end crash types. The effects of offset distance and direction were analyzed and incorporated into the models. Compared to conventional four-leg intersections, offset-T intersections exhibited 35 percent more crashes regardless of the offset distance or direction. Considering crash types, single motor vehicle crashes occurred more frequently at offset-T intersections, and increased as the offset distance increased. Rear end crashes also occurred more frequency at offset-T intersections, with left offsets having more crash occurrence than right offsets. However, angle crashes are 40 to 69 percent lower at offset-T intersections due to the elimination of the direct crossing maneuver. The CMF for converting an existing offset-T into a conventional four-leg intersection is 0.74 within the studied ranges of offset direction and distance. This equivalates to a 26 percent reduction in total (non-animal) crash frequency. At curved corner intersections, a random intercept negative binomial models for crash occurrence used geographic region as a random effect. A total intersection crash (non-animal) model was generated based on 10 years of crash data from a sample of 227 three-leg sites and 65 four-leg sites among curved corner intersection geometry only. Reliance on the availability of minor road AADT so severely limited the sample population that an estimation of minor road AADT was made in order to proceed with modeling. A minor road AADT estimation model uses national functional classification as well as surface type, population density, and major road traffic volume to estimate the minor road traffic. A table of CMFs is presented for potentially converting an existing configuration into a combined/merged approach that is consistent with a traditional countermeasure from MDOT Geometric Design Guidelines. At curved corner intersections, installing a combined/merged intersection approach near the midpoint of the curve is a potential countermeasure that can be expected to reduce the average intersection crash frequency by 25 percent for three-leg configurations. A larger radius of curvature along the curved segment at these types of intersections is also very favorable for safety performance. Each 100-foot increase in the radius of a three-leg or four-leg curved corner intersection is estimated to reduce crash occurrence by 5 percent and 8 percent respectively.The safety influence of intersection skew angle on rural two-lane two-way facilities was evaluated by calibrating crash modification factors. Ten years of crash history among federal aid and non-federal aid highways was used to develop crash modification functions at three-leg and four-leg stop-controlled intersections. Skew angle was investigated as a parameter in the SPF models both as a continuous variable, with observed values ranging from 0 to 80 degrees, and categorized into ranges. A few transformations of the skew parameter were considered such as the flexible form model having skew interaction with AADT (annual average daily traffic), and a Hoerl curve. Both three-leg and four-leg intersections exhibited an initially increasing trend of crash rates followed by a decreasing trend as skew angle increased. A categorical model was found to best describe the skew relationship using discrete skew angle ranges. Among three-leg intersections, a skew angle between 17 to 27 degrees experienced 22 percent more crashes than perpendicular intersections. However, more highly skewed three-leg intersections exhibited a decreasing relationship to increasing skew angle. Among four-leg intersections, a skew angle between 17 to 27 degrees experienced 40 percent more crashes, while intersections with a skew angle greater than 45 degrees did not have significantly different crash occurrence than perpendicular intersections. The implications of assuming a monotonic increasing relationship to skew angle are challenged as a result of this study. Multi-leg intersections with more than four approach legs constitute a rare circumstance, yet these sites experience higher than average crash frequencies compared to conventional four-leg intersections. Single-vehicle as well as angle and rear-end crash types are most likely to occur at multi-leg intersections based on the history of crashes observed.The procedures described in this study are consistent with the Highway Safety Manual (HSM) and subsequent state of the art research for the procurement of safety performance models for any variety of circumstances. By utilizing an expansive data set and geospatial mapping techniques, the analysis is extended to previously unexplored site types. The extension of predictive safety analysis to atypical intersection types with unique geometric characteristics helps to fill a gap in the current field of practice with the hope of achieving an ultimate goal toward zero deaths in motor vehicle transportation.
Assessing Safety Performance Of Roadway Characteristics In Rural And Urban Contexts
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Author : Meghna Chakraborty
language : en
Publisher:
Release Date : 2022
Assessing Safety Performance Of Roadway Characteristics In Rural And Urban Contexts written by Meghna Chakraborty and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Electronic dissertations categories.
Evaluating the safety performance of roadway segments and intersections typically involves associating traffic crashes, injuries, and fatalities to various roadway and traffic characteristics, which typically vary broadly between rural and urban contexts. In rural areas, roadway geometric characteristics often play a critical role in the safety performance of a given roadway, while myriad other factors, including driveways and intersections, tend to have a greater influence on urban roadway safety. However, certain geometric aspects, such as the characteristics of the horizontal curvature and the impact of driveway land-use type have not been well-explored in prior roadway safety research. There has also been limited research on the safety performance for roadways of lower functional classifications, such as minor arterial and collector roadways, which comprise a substantial portion of the nationwide roadway network but are often designed to lower standards and possess driver and trip characteristics that typically differ from those of principal arterials. Therefore, assumptions made on the general effect of the predictor variables from typical safety performance functions may not apply to lower roadway classes. This research sought to explore those gaps in the roadway safety research domain. To accomplish this objective, roadway characteristics were collected along with traffic volume and crash data for greater than 13,000 miles of two-lane roadways in rural, urban, and suburban areas from across the state of Michigan for the period of 2011 through 2018. A series of safety performance functions were developed using a mixed-effects negative binomial modeling structure, which included fixed-effects and random-effects to account for the unobserved heterogeneity associated with varying design standards and site characteristics. The results indicated that driveway density significantly influences crash occurrence across all land-use categories for paved highways, although no impact was observed on unpaved roads. Commercial driveways possessed a stronger effect on crash occurrence than residential driveways or industrial driveways. In urban areas, posted speed limit had a significant positive association with crash frequency, and this effect increased when the speed limit exceeded 40 mph. The effect of speed limit was stronger on urban minor arterial segments (compared to collectors) and for fatal and injury crashes (compared to property damage only). This research also assessed the safety impacts associated with horizontal curve characteristics on rural highway segments, including curve type, curve direction, curve-approaching, curve-following, and inner-curve tangent distances, and curve design speed on rural two-lane undivided highways. Similar to prior research, curves with design speeds lower than the posted speed limit showed elevated crash occurrence. Most notably, compound and reverse curves were associated with greater crash occurrence compared to simple curves, with the greatest impact by the reverse curves. The increased approaching tangent distance for the simple curve or the first of a series of compound or reverse curves increased crash likelihood, perhaps due to the decreased driver expectancy for curvature with increasing tangent distance. However, increased inner-curve tangent distance was found to be associated with decreased crash occurrence. Lastly, the left-turning curves were found to be associated with greater crash occurrence than that on the right-turning curves.
Safety And Operational Effects Of Geometric Design Features For Two Lane Highway
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Author : National Highway Institute (U.S.)
language : en
Publisher:
Release Date : 2003
Safety And Operational Effects Of Geometric Design Features For Two Lane Highway written by National Highway Institute (U.S.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Rural roads categories.
Prediction Of The Expected Safety Performance Of Rural Two Lane Highways
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Author : Douglas W. Harwood
language : en
Publisher:
Release Date : 2000
Prediction Of The Expected Safety Performance Of Rural Two Lane Highways written by Douglas W. Harwood and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with Low-volume roads categories.
This report presents an algorithm for predicting the safety performance of a rural two-lane highway. The accident prediction algorithm consists of base models and accident modification factors for both roadway segments and at-grade intersections on rural two-lane highways. The base models provide an estimate of the safety performance of a roadway or intersection for a set of assumed nominal or base conditions. The accident modification factors adjust the base model predictions to account for the effects on safety for roadway segments of lane width, shoulder width, shoulder type, horizontal curves, grades, driveway density, two-way left-turn lanes, passing lanes, roadside design and the effects on safety for at-grade intersections of skew angle, traffic control, exclusive left- and right-turn lanes, sight distance, and driveways. The accident prediction algorithm is intended for application by highway agencies to estimate the safety performance of an existing or proposed roadway. The algorithm can be used to compare the anticipated safety performance of two or more geometric alternatives for a proposed highway improvement. The accident prediction algorithm includes a calibration procedure that can be used to adapt the predicted results to the safety conditions encountered by any particular highway agency on rural two-lane highways. The algorithm also includes an Empirical Bayes procedure that can be applied to utilize the safety predictions provided by the algorithm together with actual site-specific accident history data.
Recent Roadway Geometric Design Research For Improved Safety And Operations
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Author : Marcus Brewer
language : en
Publisher: Transportation Research Board
Release Date : 2012
Recent Roadway Geometric Design Research For Improved Safety And Operations written by Marcus Brewer 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 2012 with Technology & Engineering categories.
RB’s National Cooperative Highway Research Program (NCHRP) Synthesis 432: Recent Roadway Geometric Design Research for Improved Safety and Operations reviews and summarizes roadway geometric design literature completed and published from 2001 through early 2011, particularly research that identified impacts on safety and operations.