Safety Performance of Flashing Yellow Arrow for Protected–Permissive Left-Turn Signal Control in Central Illinois

2017 ◽  
Vol 2636 (1) ◽  
pp. 32-42 ◽  
Author(s):  
Kerrie L. Schattler ◽  
Eric P. Anderson ◽  
Trevor Hanson
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Left Turn ◽  
Turn Signal ◽  
Crash Data ◽  
Flashing Yellow Arrow ◽  
Before And After ◽  
Control Research ◽  
Central Illinois ◽  
Yellow Arrow

In 2010, the Illinois Department of Transportation began implementing the flashing yellow arrow (FYA) at intersections operating with protected–permissive left-turn (PPLT) control. Research was conducted to evaluate the safety-effectiveness of FYAs at 86 intersections and 164 approaches in central Illinois. The effectiveness evaluation was performed with 3 years of before-and-after FYA installation crash data and the empirical Bayes method. In the before condition, the left-turn signals operated with a circular green display indicating the permissive interval of PPLT control using a five-section signal head. In the after condition, the FYA replaced the circular green display for the permissive interval of PPLT with a four-section signal head. Supplemental traffic signs were mounted on the mast arm adjacent to the left-turn signal at over half of the FYA installations. The results of the comprehensive safety evaluation of the FYA for PPLT control are presented. Analyses were also performed to assess the effects of the FYA supplemental signs and the effects of the FYA overall on two subsets of at-fault drivers: older drivers (age 65+) and younger drivers (age 16 to 21). The resulting mean crash modification factors for the targeted crash types ranged from 0.589 to 0.714. The findings of this research support the continued use of FYAs for PPLT control to improve safety at signalized intersections in central Illinois.

Safety Effects of Flashing Yellow Arrows Used in Protected Permitted Phasing: Comparison of Full Bayes and Empirical Bayes Results

2018 ◽  
Vol 2672 (21) ◽  
pp. 20-29 ◽  
Author(s):  
Justice Appiah ◽  
F. Adam King ◽  
Michael D. Fontaine ◽  
Benjamin H. Cottrell
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Left Turn ◽  
Flashing Yellow Arrow ◽  
Before And After ◽  
Credible Intervals ◽  
Degree Of Confidence ◽  
Crash Reduction ◽  
Better Than ◽  
Bayes Approach

Using the flashing yellow arrow (FYA) signal indication for the permissive portion of protected-permissive left-turn (PPLT) phasing has become an increasingly popular treatment for left-turn signals as drivers are believed to understand the FYA better than the traditional circular green indication. A before-and-after safety evaluation of deploying FYA at PPLT signals at 28 intersections in Virginia was conducted. Each of the study intersections had FYA for the permitted portion of the phase on at least one left-turn approach. The focus was on left-turns that operated in the protected-permissive mode (with circular green indication for the permissive portion) before being converted to PPLT operations with the FYA indication for the permissive portion (PPLT-FYA). Crash records from before and after the activation of FYA were compared using both the full Bayes and empirical Bayes approaches. The results indicate that using the FYA signal indication instead of the circular green indication had a statistically significant effect in reducing overall frequency and severity of crashes. For the intersections studied in this research, total crashes reduced by 12% following conversion from PPLT to PPLT–FYA. The results also indicated that the full Bayes approach to safety effectiveness evaluation can, at a minimum, provide similar results to the well-established empirical Bayes approach. The 95% credible intervals for the expected crash reduction rates estimated with the full Bayes method were generally narrow, suggesting a good degree of confidence in the estimates.

Crash Modification Factors for the Flashing Yellow Arrow Treatment at Signalized Intersections

2018 ◽  
Vol 2672 (30) ◽  
pp. 142-152 ◽  
Author(s):  
Raghavan Srinivasan ◽  
Bo Lan ◽  
Daniel Carter ◽  
Sarah Smith ◽  
Kari Signor
Keyword(s):  
North Carolina ◽  
Empirical Bayes ◽  
Evaluation Method ◽  
Signalized Intersections ◽  
Left Turn ◽  
Flashing Yellow Arrow ◽  
Crash Modification Factors ◽  
Treatment Category ◽  
Using Data ◽  
Yellow Arrow

This paper presents the results of an evaluation of the flashing yellow arrow (FYA) treatment using data from signalized intersections in Nevada, North Carolina, Oklahoma, and Oregon. The evaluation method was an empirical Bayes before–after analysis. The treatments were divided into seven categories depending on the phasing system in the before period (permissive, protected–permissive, or protected), phasing system in the after period (FYA permissive or FYA protected–permissive), the number of roads where the FYA was implemented (one road or both roads), and the number of legs at the intersections (three or four). The first five treatment categories involved permissive or protected–permissive phasing in the before period. Intersections in these five treatment categories experienced a reduction in the primary target crashes under consideration: left turn crashes and left turn with opposing through crashes. The reduction ranged from 15% to 50%, depending on the treatment category. Intersections that had at least one protected left turn phase in the before period and had FYA protected–permissive left turn phase in the after period experienced an increase in left turn crashes and left turn with opposing through crashes, indicating that replacing a fully protected left turn with FYA will likely cause an increase in left turn crashes.

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.

Safety effects of traffic signing for left turn flashing yellow arrow signals

2015 ◽  
Vol 75 ◽  
pp. 252-263 ◽  
Author(s):  
Kerrie L. Schattler ◽  
Cody J. Gulla ◽  
Travis J. Wallenfang ◽  
Beau A. Burdett ◽  
Jessica A. Lund
Keyword(s):  
Left Turn ◽  
Flashing Yellow Arrow ◽  
Yellow Arrow

Traffic Safety Evaluation of Video Advertising Signs

2005 ◽  
Vol 1937 (1) ◽  
pp. 105-112 ◽  
Author(s):  
Alison Smiley ◽  
Bhagwant Persaud ◽  
Geni Bahar ◽  
Calvin Mollett ◽  
Craig Lyon ◽  
...  
Keyword(s):  
Traffic Safety ◽  
Safety Evaluation ◽  
Driver Distraction ◽  
Eye Fixation ◽  
Crash Data ◽  
Video Advertising ◽  
Urban Expressway ◽  
Public Survey ◽  
Before And After ◽  
The Right

Road authorities are under increasing pressure from advertisers to allow video advertising in the right-of-way but are understandably concerned about whether video signs constitute a driving hazard. At the City of Toronto's request, a comprehensive assessment of traffic safety impacts related to such signs was carried out in a series of studies involving three downtown intersections and an urban expressway site. An on-road eye fixation study was carried out to determine if drivers look at video advertising signs. Conflict studies were conducted to determine if there were more conflicts on intersection approaches with visible video signs than on those without such signs. A before-and-after sign installation study of headways and speeds on the urban expressway was carried out. Crashes were compared before and after sign installation at the expressway and three intersection sites. Finally, a public survey was conducted to determine if video advertising was perceived to affect traffic safety. On the basis of the eye fixation study and the public survey data, it is apparent that video advertising can distract drivers inappropriately and lead to individual crashes. However, the evidence from other studies was not consistent and suggests that for the particular signs studied, overall impacts on traffic safety are likely to be small. Further studies, especially prospective ones with larger crash data sets, are required to be certain about the findings. A comparison between this study and an earlier one suggests that there are large differences in driver distraction depending on the placement and the environment in which the sign is seen. Further studies are required to determine factors that minimize driver distraction.

Safety Evaluation of Alternative Audible Lane Departure Warning Treatments in Reducing Traffic Crashes: An Empirical Bayes Observational Before–After Study

2018 ◽  
Vol 2672 (21) ◽  
pp. 30-40 ◽  
Author(s):  
Lingtao Wu ◽  
Srinivas R. Geedipally ◽  
Adam M. Pike
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Highway Safety ◽  
Warning Systems ◽  
Lane Departure Warning ◽  
Crash Data ◽  
Pavement Markings ◽  
Lane Departure ◽  
Run Off ◽  
Single Vehicle

Roadway departure crashes are a major contributor to traffic fatalities and injury. Rumble strips have been shown to be an effective countermeasure in reducing roadway departure crashes. However, some roadway situations, for instance, inadequate shoulder width or roadway surface depth, have limited the application of conventional milled or rolled in rumble strips. Alternative audible lane departure warning systems, including profile (audible) pavement markings and preformed rumble bars, are increasingly used to overcome the limitations that exist with the milled rumble strips. So far, the safety effectiveness of these alternative audible lane departure warning systems has not been extensively assessed. The main purpose of this paper is to examine the safety effect of installing profile pavement markings and preformed rumble bars. Specifically, this study developed crash modification factors for these treatments that quantify the effectiveness in reducing single-vehicle-run-off-road (SVROR) and opposite-direction (OD) crashes. Traffic, roadway, and crash data at the treated sites on 189 miles of rural two-lane highways in Texas were analyzed using an empirical Bayes (EB) before–after analysis method. Safety performance functions from the Highway Safety Manual and Texas Highway Safety Design Workbook were used in the EB analysis. The results revealed a 21.3% reduction in all SVROR and OD crashes, and 32.5% to 39.9% reduction in fatal and injury SVROR and OD crashes after installing profile pavement marking and preformed rumble bars.

scholarly journals Safety Evaluation of Shoulder Bypass Lanes at Unsignalized Intersections on Rural Two-Lane Roadways Using Cross Sectional Analysis

2016 ◽  
Author(s):  
Sunanda Dissanayake ◽  
Alireza Shams
Keyword(s):  
Low Cost ◽  
Safety Evaluation ◽  
Cross Sectional Study ◽  
Highway Safety ◽  
Sectional Study ◽  
Cross Sectional ◽  
Crash Data ◽  
Study Approach ◽  
Unsignalized Intersections ◽  
Before And After

Construction of bypass lanes at rural intersections has typically been considered a low-cost highway safety improvement by the transportation community. However, this needs to be quantitatively evaluated so that the decisions could be made on whether to continue with adding bypass lanes. Highway safety analyses utilize two common approaches to evaluate the effectiveness of a geometric treatment: before-and-after study and cross-sectional study. This paper explains the results using a cross-sectional study approach, where intersections with bypass lanes were compared to intersections with no bypass lanes for which crash data were obtained for more than 1,100 intersections in Kansas. Both 3-legged and 4-legged intersections were taken into consideration separately by looking at intersection-related crashes and crashes within an intersection box. According to the results, the number of crashes and crash severities were lower at 3-legged intersections with bypass lanes compared with 3-legged intersections without bypass lanes, even though these reductions were not statistically significant at 95% level. When considering a 300-ft. intersection box, statistically significant crash reductions were observed at 4-legged intersections, for all considered crash and crash rate categories. When considering 90% level, crash reduction at 3-legged intersections was also statistically significant when considering a 300-ft. intersection box. Crash modification factors (CMFs) calculated to evaluate safety effectiveness of bypass lanes at unsignalized rural intersections in Kansas showed values less than 1.0 for almost all cases, indicating safety benefits of bypass lanes. Accordingly, it is beneficial to continue with the practice of adding shoulder bypass lanes at rural unsignalized intersections on two-lane roads where the traffic volumes are relatively low.

Evaluation of the Flashing Yellow Arrow (FYA) Permissive Left-Turn in Shared Yellow Signal Sections

2014 ◽  
Author(s):  
David A. Noyce ◽  
Andrea R. Bill ◽  
Jr. Michael A. ◽  
◽  
◽  
...  
Keyword(s):  
Left Turn ◽  
Flashing Yellow Arrow ◽  
Yellow Arrow

scholarly journals Safety Effectiveness of Intersection Left- and Right-Turn Lanes

2003 ◽  
Vol 1840 (1) ◽  
pp. 131-139 ◽  
Author(s):  
Douglas W. Harwood ◽  
Karin M. Bauer ◽  
Ingrid B. Potts ◽  
Darren J. Torbic ◽  
Karen R. Richard ◽  
...  
Keyword(s):  
Traffic Control ◽  
Empirical Bayes ◽  
Matched Pair ◽  
Left Turn ◽  
Before And After ◽  
Accident Data ◽  
Left And Right ◽  
Safety Effectiveness ◽  
Evaluation Approaches ◽  
Control Traffic

The results of research involving a well-designed before-and-after evaluation of the safety effects of providing left- and right-turn lanes for at-grade intersections are presented. Geometric design, traffic control, traffic volume, and traffic accident data were gathered for a total of 280 improved intersections as well as 300 similar intersections that were not improved during the study period. The types of improvement projects evaluated included installation of added left-turn lanes, added right-turn lanes, and extension of the length of existing left- or right-turn lanes. An observational before-and-after evaluation of these projects was performed by using several alternative evaluation approaches. Three contrasting approaches to before-and-after evaluation were used: the yoked comparison or matched-pair approach, the comparison group approach, and the empirical Bayes approach. The research not only evaluated the safety effectiveness of left- and right-turn lane improvements but also compared the performances of these three alternative approaches in making such evaluations. The research developed quantitative safety effectiveness measures for installation design improvements involving added left-turn lanes and added right-turn lanes. The research concluded that the empirical Bayes method provides the most accurate and reliable results. Further use of this method is recommended.

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