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.

Effect on Vehicle-Pedestrian Conflicts of “Turning Traffic Must Yield to Pedestrians” Sign

1996 ◽  
Vol 1553 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Husham N. Abdulsattar ◽  
Mohammed S. Tarawneh ◽  
Patrick T. McCoy ◽  
Stephen D. Kachman
Keyword(s):  
Traffic Control ◽  
Signalized Intersections ◽  
Legal Obligation ◽  
Left Turn ◽  
Right Of Way ◽  
Two Cities ◽  
Before And After ◽  
Left And Right ◽  
Control Devices ◽  
The Right

Left- and right-turn movements at signalized intersections have been found to be three to six times more hazardous to pedestrians than through movements mainly because drivers fail to observe or yield the right of way to pedestrians. The objective was to evaluate the Turning Traffic Must Yield to Pedestrians sign, which was aimed at reminding turning motorists of their legal obligation to yield the right of way to pedestrians and, consequently, reducing vehicle-pedestrian conflicts. The sign was installed at 12 marked crosswalks in two cities, and vehicle-pedestrian conflict data were collected before and after its installation. The sign was effective in reducing left-turn conflicts 20 to 65 percent and right-turn conflicts 15 to 30 percent; both reductions were statistically significant at the 0.05 level. The sign was significantly more effective in reducing left-turn conflicts than it was for right-turn conflicts. Percentage conflicts between pedestrians and turning traffic decreased as the pedestrian group size increased. In other words, larger pedestrian group sizes encountered fewer conflicts with turning traffic. This result is true for both left- and right-turn movements, regardless of the presence of the sign. Based on the results of this study, it was recommended that the “Turning Traffic Must Yield to Pedestrians” sign be considered for inclusion in the Manual on Uniform Traffic Control Devices.

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.

scholarly journals Observational Before and After Safety Study of Installing Signals at Rural Intersections: Using the Empirical Bayes (EB) and Conventional Methods

2021 ◽  
Author(s):  
Ravindranauth Bhim
Keyword(s):  
Economic Benefit ◽  
Empirical Bayes ◽  
Signal Control ◽  
Percent Reduction ◽  
Safety Study ◽  
Left Turn ◽  
Before And After ◽  
Conventional Methods ◽  
Safety Effect ◽  
Crash Types

Signalizing an intersection usually results in a reduction in right-angle and left-turn crashes, and an increase in rear-end crashes. This study used the conventional and Empirical Bayes (EB) before and after methods on 45 treated sites (converted from stop to signal control) in California and Minnesota to estimate the safety effect of having signals installed. The results confirm the belief that right-angle and left-turn crashes are reduced and rear-end crashes increase. However, these effects cannot be used to quantitatively assess the benefit gained from the reduction in right-angle and left-turn crashes against the increase in rear-end crashes, simply because crash types have different severities. By performing an economic examination of the safety effects, this study was able to show that by installing signals on 45 treated sites, there was a positive aggregate economic benefit of $155,883,978 which represents a 69 percent reduction in cost. This translated into $616,142 per site-year.

scholarly journals Observational Before and After Safety Study of Installing Signals at Rural Intersections: Using the Empirical Bayes (EB) and Conventional Methods

2021 ◽  
Author(s):  
Ravindranauth Bhim
Keyword(s):  
Economic Benefit ◽  
Empirical Bayes ◽  
Signal Control ◽  
Percent Reduction ◽  
Safety Study ◽  
Left Turn ◽  
Before And After ◽  
Conventional Methods ◽  
Safety Effect ◽  
Crash Types

Signalizing an intersection usually results in a reduction in right-angle and left-turn crashes, and an increase in rear-end crashes. This study used the conventional and Empirical Bayes (EB) before and after methods on 45 treated sites (converted from stop to signal control) in California and Minnesota to estimate the safety effect of having signals installed. The results confirm the belief that right-angle and left-turn crashes are reduced and rear-end crashes increase. However, these effects cannot be used to quantitatively assess the benefit gained from the reduction in right-angle and left-turn crashes against the increase in rear-end crashes, simply because crash types have different severities. By performing an economic examination of the safety effects, this study was able to show that by installing signals on 45 treated sites, there was a positive aggregate economic benefit of $155,883,978 which represents a 69 percent reduction in cost. This translated into $616,142 per site-year.

Study of Intersection Accidents by Maneuver Type

2002 ◽  
Vol 1784 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Sudeshna Mitra ◽  
Hoong Chor Chin ◽  
Mohammed Abdul Quddus
Keyword(s):  
Traffic Control ◽  
Traffic Accidents ◽  
Signalized Intersections ◽  
Probability Models ◽  
Left Turn ◽  
Factors Affecting ◽  
Adaptive Signal Control ◽  
Road Geometry ◽  
Accident Data ◽  
Adaptive Signal

Studies dealing with the effect of road geometry on accidents by vehicle maneuvers have been reported, mostly for western countries and a few for Asia. However, no such studies have been reported for Singapore. Traffic accidents arising from head-to-side and head-to-rear maneuvers at four-legged signalized intersections in Singapore were investigated. Based on accident data at intersections in the southwestern part of Singapore from 1992 to 1999, the factors affecting such accidents were explored using zero-altered probability models. Specific roadway geometries as well as traffic control and regulatory factors that influence the two categories of accidents were identified. It was found that head-to-side accidents tend to decrease if there is an adjacent intersection within 200 m and if bus stops along the approach are provided with bays. On the other hand, longer sight distances and the presence of a pedestrian refuge tend to increase this type of accident. Higher speed limits were found to reduce the instances of zero head-to-side accidents. It was also found that head-to-rear accidents decrease when the intersections are under adaptive signal control but increase when surveillance cameras are present. There is also some evidence to suggest that the presence of an uncontrolled left-turn channel, the existence of medians wider than 2 m, higher approach volumes, and more phases per cycle all contribute to higher instances of accidents by both maneuver types.

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.

scholarly journals Evaluation of the Use of a Road Diet Design: An Urban Corridor Case Study in Washington, DC

2021 ◽  
Vol 13 (16) ◽  
pp. 8964
Author(s):  
Mohammad A. Aljamal ◽  
Derek Voight ◽  
Jacob Green ◽  
Jianwei Wang ◽  
Huthaifa I. Ashqar
Keyword(s):  
Empirical Bayes ◽  
Annual Number ◽  
Full Time ◽  
Left Turn ◽  
The Road ◽  
Traffic Calming ◽  
Before And After ◽  
Traffic Volumes ◽  
Bayes Analysis ◽  
Urban Corridor

A traditional road diet design converts a four-lane two-way road to a three-lane road consisting of two through lanes and a center two-way left turn lane. This paper introduces a new application of the road diet design in an urban corridor. Specifically, the new application converts a four-lane two-way road into a two-lane two-way road with full-time parking lanes in both directions. The paper analyzed the traffic impacts of the road diet application on the corridor of New Jersey Avenue, northwest, in the city of Washington, District of Columbia. The corridor included five signalized and one unsignalized intersections. Before-and-after analyses using Synchro 11 simulation and Site-Specific Empirical Bayes analysis were used to evaluate and compare existing and proposed scenarios. The proposed scenario provided various benefits including offering accessibility to the businesses in the area and acting as a traffic calming strategy. For signalized intersections, the overall performance remained the same for most intersections except for one intersection (on P Street), as it is significantly impacted by the road diet design due to the dramatic increase of traffic volumes in its minor streets as a result of diverting traffic volumes from the unsignalized intersection for left and through movements. Results showed that the use of a road diet design enhanced the unsignalized intersection performance due to the traffic volume divergence from its minor streets and enhanced the safety of the study area by decreasing the annual number of predicted crashes. To achieve better operational benefits and reflect traffic demands, the paper recommends to re-optimize signal timings when a road diet design is adopted.

scholarly journals Effect of dental wear, stabilization appliance and anterior tooth reconstruction on mandibular movements during speech

2008 ◽  
Vol 19 (2) ◽  
pp. 151-158 ◽  
Author(s):  
Priscila de Oliveira Serrano ◽  
Fernanda Faot ◽  
Altair Antoninha Del Bel Cury ◽  
Renata Cunha Matheus Rodrigues Garcia
Keyword(s):  
Tooth Wear ◽  
Anterior Tooth ◽  
Control Group ◽  
Dental Wear ◽  
Jaw Opening ◽  
Before And After ◽  
Left And Right ◽  
The Right ◽  
Tracking Device ◽  
Mandibular Movements

This study described changes in mandibular movements during pronunciation of /m/ and /s/ sounds in Portuguese, in patients presenting dental wear before and after appliance insertion and tooth reconstruction. Subjects were divided into a control group of dentate patients and an experimental group of patients with incisal tooth wear due to bruxism. A magnetic jaw tracking device measured the jaw opening, and translations to left and right sides of the mandible during pronunciation of phonemes. Evaluations were carried out 1 week and immediately before appliance insertion; 24 h, 7, 30 and 60 days after appliance insertion; and 1 week and 1 month after tooth reconstruction. Data were submitted to two-way ANOVA, Mann-Whitney and Friedman tests (p<0.05). Jaw opening was different (p<0.05) for both sounds in all periods. The anteroposterior amplitude for /s/ showed differences immediately before and 1 month after appliance insertion (p<0.05). Lateral amplitude for the right side showed differences between groups after appliance insertion for /s/, and 1 and 2 months after appliance insertion for the /m/ (p<0.05). Volunteers with anterior tooth wear had a wider opening movement, and the movements during speech of /m/ and /s/ sounds were not changed after appliance insertion and reconstruction of teeth.

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.

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