Evaluating the Safety Effects of Span Wire to Mast Arm Signal Conversion

2018 ◽  
Vol 2672 (30) ◽  
pp. 21-31 ◽  
Author(s):  
Zulqarnain H. Khattak ◽  
Michael D. Fontaine
Keyword(s):  
Road Safety ◽  
Empirical Bayes ◽  
Comprehensive Evaluation ◽  
Department Of Transportation ◽  
Crash Data ◽  
Signal Conversion ◽  
Modification Factor ◽  
Virginia Department ◽  
Crash Types ◽  
Safety Benefit

The mast arm signal mounting configuration has often been assumed to provide greater conspicuity and visibility than span wire installations, but the impacts of this countermeasure on road safety have not been well established quantitatively. This paper’s intent is to provide a comprehensive evaluation of safety effects of converting span wire installations to mast arm installations. An Empirical Bayes before–after safety analysis was conducted using crash data for 30 intersections collected from the Virginia Department of Transportation (VDOT). A crash type analysis was also conducted to observe changes in crash types. Based on the data available, no statistically significant improvement in safety was found. Average crash modification factor (CMF) values of 0.97 and 0.98 were observed for total and fatal and injury crashes, but these CMFs were not statistically significant. A reduction in the proportion of angle crashes was observed, but the change was not statistically significant and the overall distribution of crashes did not change significantly after converting signal configurations from span wire to mast arm. Although mast arm deployments may offer advantages in maintenance costs and aesthetics, there does not appear to be a substantial safety benefit to these conversions.

Safety Evaluation of Change in Posted Speed Limit from 65 to 70 mph on Rural Virginia Interstate System

2018 ◽  
Vol 2672 (38) ◽  
pp. 35-45
Author(s):  
Scott Himes ◽  
Frank Gross ◽  
Michael Nichols ◽  
Mena Lockwood
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Speed Limit ◽  
Department Of Transportation ◽  
Run Off ◽  
Adjustment Factors ◽  
Interstate System ◽  
Virginia Department ◽  
Crash Types ◽  
Disaggregate Analysis

Effective July 1, 2010, the Virginia Department of Transportation (VDOT) increased the maximum posted speed limit on interstates and similar facilities from 65 to 70 mph, if recommended following an engineering study. As a result, VDOT performed engineering studies on selected rural interstates posted at 65 mph. By November 2010, VDOT had increased the speed limit from 65 to 70 mph for approximately 670 centerline miles of select rural interstates. This paper presents the results of an empirical Bayes before–after study into the safety and operational effects of the speed limit increase. The analysis focused on total, injury, run-off-road, and truck-related crashes. Comparison segments were used to develop annual adjustment factors, account for regional differences, and identify underlying crash trends in the period before the speed limit increase. At the aggregate level, the results indicated no increase in any of the focus crash types after the increase. Focusing on sites without other changes, the increased speed limit did not increase or decrease any of the crash types. The disaggregate analysis provided further insight into the circumstances in which the change in posted speed limit had more and less pronounced impacts; specifically, that segment type (base or interchange) influenced safety: interchange segments observed statistically significant increases in total, run-off-road, and truck-related crashes. The disaggregate analysis also showed that roadway improvements may help to offset the safety impact of increasing the posted speed limit.

Safety Effects of Turning Movement Restrictions at Stop-Controlled Intersections

2018 ◽  
Vol 2672 (21) ◽  
pp. 10-19
Author(s):  
Thanh Q. Le ◽  
Frank Gross ◽  
Tim Harmon
Keyword(s):  
Confidence Level ◽  
Cost Effective ◽  
Cross Sectional ◽  
Benefit Cost Analysis ◽  
Crash Data ◽  
Crash Modification Factors ◽  
Design Speed ◽  
Benefit Cost ◽  
Crash Types ◽  
Safety Benefit

This study evaluates the safety effectiveness of physical right-in-right-out (RIRO) operations compared with full turning movements at stop-controlled intersections. Geometric, traffic, and crash data from California were obtained for urban, three-legged, stop-controlled intersections with full movement and RIRO operations, as well as the downstream four-legged, stop-controlled or signalized intersections with full movement. A cross-sectional analysis provided estimates of the effects of turning movement restrictions while controlling for other differences between sites with RIRO and full movement. The aggregate results indicate reductions in total, all intersection-related, and fatal and injury intersection-related crashes at intersections with RIRO operations compared with full movement, with estimated crash modification factors of 0.55, 0.32, and 0.20, respectively. The reductions are statistically significant at the 95% confidence level for all crash types. Based on the disaggregate results, it does not appear that RIRO operations have different effects for different levels of traffic, design speed, or number of lanes. The analysis also examined the potential for crash migration from intersections where RIRO is implemented to the downstream intersection when determining the net benefits. The results indicate potential crash increases at downstream intersections, but many of the increases are not statistically significant at the 90% confidence level. Although the safety benefit-cost analysis suggests the strategy can be cost effective in reducing crashes at stop-controlled intersections, there is a need to analyze potential costs and benefits on a case-by-case basis with site-specific values.

scholarly journals Safety evaluation of roundabouts at freeway ramp terminals and HSM calibration

2017 ◽  
Author(s):  
◽  
Jacob A. Berry
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Crash Severity ◽  
Site Specific ◽  
Crash Data ◽  
Highway Safety Manual ◽  
Time Period ◽  
Using Data ◽  
Crash Types ◽  
Project Level

Although the conventional understanding is that roundabouts have the potential to improve safety at intersections, particularly by reducing more severe crash types, there is limited knowledge on their safety impacts when utilized as part of an interchange system. This research utilizes multiple years of crash, traffic, and geometric data across a variety of roundabout interchange sites in Missouri to develop a two-level Empirical Bayes (EB) safety analysis at the project (entire interchange) and site-specific (ramp terminal only) levels. The results were then aggregated for both single-lane and dual-lane roundabout terminals. The project-level results for single-lane sites showed a decrease in fatal/injury crashes (FI) by 20.3 percent, property damage only (PDO) crashes by 26.0 percent and total crashes by 24.5 percent. The site-specific results for single-lane roundabout terminals indicated a reduction of FI crashes by 32.8 percent, PDO crashes by 23.1 percent, and total crashes by 24.4 percent. At the project-level, dual-lane roundabouts were shown to reduce FI crashes by 2.3 percent while increasing PDO and total crashes by 16.9 percent and 12.2 percent, respectively. The dual-lane site-specific results indicated an increase in FI crashes by 34.7 percent, PDO crashes by 53.9 percent, and total crashes by 50.0 percent at the ramp terminal specifically. This analysis directly compares observed crash data after roundabout implementation to the expected number of crashes over that time period if the roundabout were never constructed. Therefore, this indicates that single-lane roundabouts performed significantly better than their original configurations, while the dual-lane roundabout terminals were shown to be less-suitable for certain applications. Additionally, it was found that a high proportion of the roundabout crashes occurred at the exit ramp approach legs; this was illustrated in the collision diagrams and crash type distributions that were produced for the common observed crashes at both single and dual-lane roundabout terminals. As a separate part of this thesis research, an improved calibration of the Highway Safety Manual safety performance functions of four facility types was performed using data from 2012-2014 to calibrate for local Missouri conditions. Crash severity and crash type distributions were also developed for each facility type.

Bridge Substructure Repairs with Self-Consolidating Concrete and Galvanic Anodes

2018 ◽  
Vol 2672 (27) ◽  
pp. 56-64
Author(s):  
H. Celik Ozyildirim ◽  
Stephen R. Sharp
Keyword(s):  
Chloride Content ◽  
Visual Observation ◽  
Department Of Transportation ◽  
Corrosion Activity ◽  
Self Consolidating Concrete ◽  
Reinforced Concrete Bridge ◽  
Form Pressure ◽  
Virginia Department ◽  
Narrow Area ◽  
Chloride Contaminated

Historically, the Virginia Department of Transportation (VDOT) has repaired chloride-contaminated reinforced concrete bridge substructure elements that contain vertical and overhead sections with either shotcrete or a conventional A3 (3,000 psi) or A4 (4,000 psi) concrete. This study investigated using self-consolidating concrete (SCC), which has a high flow rate, bonds well, has low permeability, and provides smooth surfaces, as another option. The study also explored the use of galvanic anodes to control corrosion activity in SCC repairs. In VDOT’s Lynchburg and Staunton Districts, SCC repairs were made with and without the use of galvanic anodes. This provided a means for determining the benefit of using the anodes. The needed repair areas were determined by visual observation and sounding. After 7 years of service, SCC repair areas with and without anodes did not exhibit corrosion activity; small vertical cracks were evident in the SCC but did not affect performance. The anodes can provide protection to the steel immediately adjacent to the repair areas. However, unrepaired concrete areas away from the patched area with anodes now require additional repairs. SCC can be successfully placed; however, attention should be paid to form pressure and slump loss. Selection of repair areas should be based on corrosion-related measurements such as half-cell or chloride content, rather than sounding. Progression of corrosion demonstrates the necessity of removing all chloride-contaminated concrete not just adjacent to, but also away from the reinforcement, as anodes in the repair area will provide protection only in a narrow area around the patch.

Performance of Virginia’s Early Foamed Warm Mix Asphalt Mixtures

2018 ◽  
Vol 2672 (28) ◽  
pp. 178-189 ◽  
Author(s):  
Stacey D. Diefenderfer
Keyword(s):  
Dynamic Modulus ◽  
Permanent Deformation ◽  
Warm Mix Asphalt ◽  
Department Of Transportation ◽  
High Dynamic ◽  
Repeated Load ◽  
And Performance ◽  
Virginia Department ◽  
Performance Grading ◽  
Air Void

The Virginia Department of Transportation began allowing the use of warm mix asphalt (WMA) in 2008. Although several WMA technologies were investigated prior to implementation, foamed WMA was not. This study evaluated the properties and performance of foamed WMA placed during the initial implementation of the technology to determine whether the technology had performed as expected. Six mixtures produced using plant foaming technologies and placed between 2008 and 2010 were identified and subjected to field coring and laboratory testing. Coring was performed in 2014, resulting in pavement ages from 4 to 6 years. Three comparable hot mix asphalt (HMA) mixtures were cored at 5 years for comparison. Cores were evaluated for air-void contents and permeability and were subjected to dynamic modulus, repeated load permanent deformation, and overlay testing. In addition, binder was extracted and recovered for performance grading. Similar properties were found for the WMA and HMA mixtures. One WMA mixture had high dynamic modulus and binder stiffness, but overlay testing did not indicate any tendency for premature cracking. All binders had aged between two and three performance grades above that specified at construction. WMA binders and one HMA binder aged two grades higher, and the remaining two HMA binders aged three grades higher, indicating a likely influence on aging of the reduced temperatures at which the early foamed mixtures were typically produced. Overall results indicated that foamed WMA and HMA mixtures should be expected to perform similarly.

scholarly journals Safety Impacts of Converting Two-Way Left-Turn Lanes to Raised Medians and Associated Design Concerns

2016 ◽  
Author(s):  
Priyanka Alluri ◽  
Albert Gan ◽  
Kirolos Haleem
Keyword(s):  
Data Availability ◽  
Left Turn ◽  
Arterial Streets ◽  
Crash Data ◽  
Potential Safety ◽  
Before And After ◽  
Show Evidence ◽  
Crash Types ◽  
Associated Design ◽  
Urban Arterial

Raised medians and two-way left-turn lanes (TWLTLs) are the two most common types of median treatments on arterial streets. This paper aims to conduct a detailed study on the safety impacts of conversion from TWLTLs to raised medians on state roads in Florida. In addition, the study also investigated several potential safety concerns related to raised medians on state roads, including crashes at median openings, vehicles directly hitting the median curb, and median crossover crashes. Based on data availability, 17.51 miles of urban arterial sections in Florida that were converted from TWLTLs to raised medians were analyzed. Police reports of all the crashes before and after median conversion were reviewed to correct miscoded crash types and obtain additional detailed crash information. Overall, a 28.5% reduction in total crash rate was observed after the 10 study locations were converted from TWLTLs to raised medians. The reductions in the proportions of left-turn and right-turn crashes were statistically significant, while the changes in the proportions of other crash types were not statistically significant. Furthermore, the crash data did not show evidence that raised medians are an additional hazard compared with TWLTLs.

Natural Bridge, Virginia: Complementary Geotechnical Investigation and Analysis Methods for Mobility Planning

2020 ◽  
Vol 26 (2) ◽  
pp. 141-148
Author(s):  
Brian S. Bruckno ◽  
Chester F. Watts ◽  
George Stephenson ◽  
Christopher Mau
Keyword(s):  
Cultural Resources ◽  
Department Of Transportation ◽  
Geotechnical Investigation ◽  
Non Invasive ◽  
Transportation Corridor ◽  
Historic Landmark ◽  
Potential Risks ◽  
Potential Damage ◽  
Virginia Department ◽  
Privately Owned

ABSTRACT Natural Bridge, in Rockbridge County, Virginia, is a geological arch carrying U.S. Route 11 over Cedar Creek. The area has significant historical and cultural importance; it is listed on the National Register of Historic Places and is a Virginia Historic Landmark. Until 2015, the arch and area below were privately owned and operated, with only the pavement structure of U.S. Route 11 held by the Virginia Department of Transportation. Since then, the arch and area below have been leased to the Virginia Department of Conservation and Recreation, potentially transferring liability to the Commonwealth. As part of the Commonwealth's due diligence and to help ensure that the arch is preserved for future generations, the Department of Transportation, in partnership with Radford University, completed a comprehensive, non-invasive geological and geotechnical investigation in 2017 and 2018. A complementary variety of geophysical, laser, optical, seismic, and traditional geological methods of study were used to allow for integrated data analysis. The investigation revealed potential risks to the integrity of the arch, which may eventually reduce its suitability for use as a transportation corridor. The investigation methodology allowed planning for protection of the environment, cultural resources, and local economies while avoiding any potential damage to the arch. As of the date of this article, plans are under way to relocate U.S. Route 11 onto an alternate alignment entirely, thereby helping to preserve this valuable cultural, historical, and geological asset.

scholarly journals Association between Crash Attributes and Drivers’ Crash Involvement: A Study Based on Police-Reported Crash Data

2020 ◽  
Vol 17 (23) ◽  
pp. 9020
Author(s):  
Guofa Li ◽  
Weijian Lai ◽  
Xingda Qu
Keyword(s):  
Logistic Regression ◽  
Age Groups ◽  
Nearest Neighbors ◽  
Older Drivers ◽  
Driving Safety ◽  
Crash Data ◽  
Imbalance Problem ◽  
Different Types ◽  
Crash Types ◽  
Safety Enhancement

Understanding the association between crash attributes and drivers’ crash involvement in different types of crashes can help figure out the causation of crashes. The aim of this study was to examine the involvement in different types of crashes for drivers from different age groups, by using the police-reported crash data from 2014 to 2016 in Shenzhen, China. A synthetic minority oversampling technique (SMOTE) together with edited nearest neighbors (ENN) were used to solve the data imbalance problem caused by the lack of crash records of older drivers. Logistic regression was utilized to estimate the probability of a certain type of crashes, and odds ratios that were calculated based on the logistic regression results were used to quantify the association between crash attributes and drivers’ crash involvement in different types of crashes. Results showed that drivers’ involvement patterns in different crash types were affected by different factors, and the involvement patterns differed among the examined age groups. Knowledge generated from the present study could help improve the development of countermeasures for driving safety enhancement.

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