Predicting Stop Sign Compliance at All-Way Stop Intersections in Close Proximity to Signalized Intersections
Stephen Arhin, Howard UniversityShow Abstract
Adam Gatiba, Howard University
Melissa Anderson, Howard University
Melkamsew Ribbiso, Howard University
STOP signs (at unsignalized intersections) that are in close proximity to signalized intersections are often violated by drivers while “speeding up” to go through the upstream or downstream signalized intersection that have the green interval upon approach. It is thought that if the distance between the upstream or downstream signalized and the AWSC intersection is long, drivers usually comply with STOP signs at AWSC intersections. This research determined driver compliance rates (CRs) at All-Way STOP Control (AWSC) intersections that are in close proximity to upstream or downstream signalized intersections and, explored the existence of a relationship between CR and the distance between a pair of signalized and AWSC intersections. Thirty (30) isolated segments with combinations of signalized and AWSC intersections in the District of Columbia were selected for the study. Field data were obtained at each intersection in addition to observation of driver compliance with STOP signs at AWSC intersections via video playback. In all, 13,956 observations were made at 57 AWSC intersections in 2017. The study showed that lower CRs were observed at AWSC intersections that are in closer proximity to the signalized intersections. Thus, the shorter the distance from the existing AWSC to signalized intersections, the lower the CR (or higher violation rate). Based on the data obtained, a non-linear relationship between CR and distance between pairs of intersections was developed. From the model, to achieve a minimum STOP sign compliance rate of 95% at an AWSC, an optimal distance of approximately 1,300 feet between intersections is required.
Determining Length of Red Intervals for Effective Protected Permissive Left Turn Phase Operation with Flashing Yellow Arrow Signal
Muqtasid Mahbub, University of South AlabamaShow Abstract
Min-Wook Kang, University of South Alabama
Joyoung Lee, New Jersey Institute of Technology
Protected-permissive left turn (PPLT) phasing has been popular and widely used in many urban intersections in North America because of its operational benefits. A significant number of intersections have recently been upgraded with four-section signal heads with flashing yellow arrow (FYA) indication for an effective protected-permissive left turn operation. The present study seeks to find appropriate length of two red times whose roles are important, but different during the FYA-PPLT phasing. One is red time for delayed-start of permissive left turn movements; the other is additional red time for delayed-start of opposing through movements. Micro-traffic simulation and conflict analysis are explored to assess the effects of the red time length on intersection efficiency and safety. A useful reference, which describes the balanced length of the two red times under varying traffic levels, is developed as a result.
Developing a Process for Deploying Systemic Countermeasures at Unsignalized Intersections: A Virginia Case Study
Benjamin H Cottrell, Jr., Virginia Transportation Research CouncilShow Abstract
In-Kyu Lim, Virginia Department of Transportation
This paper discusses the process used to develop a safety improvement plan for unsignalized intersections using systemic low-cost countermeasures. The scope of this project focused on unsignalized intersections with stop sign control on the minor approaches. The first objective was to perform an assessment of Virginia’s unsignalized intersection crashes over a 5-year period to determine predominant crash trends and collision types to target for treatment. Four focus collision types with the highest frequency of crashes and the greatest potential reduction in crashes were 3-leg angle, 3-leg fixed object off road, 4-leg angle, and 4-leg rear-end. Chi-square automatic interaction detection (CHAID) decision tree analysis was used to perform a systemic analysis to identify a group of intersections associated with potential risk factors related to the focus collision types. A tiered list of systemic countermeasures to deploy was developed. The countermeasures were intended to warn of the stop ahead, make the stop sign and stop location more visible on the minor street, and warn of the intersection ahead on the major street. The potential for safety improvement (PSI) measure was used to prioritize the candidate treatment intersections. Before deployment, a study of the intersections by Virginia Department of Transportation district traffic engineering staff is planned to finalize the plan. The output from the research was a safety improvement plan to deploy treatments systemically to unsignalized intersections as part of the safety program.
Left Turn Crash Risk Analysis: Development to a Microsimulation Modeling Approach
Justice Appiah, Virginia Transportation Research CouncilShow Abstract
Adam King, Virginia Department of Transportation
Michael Fontaine, Virginia Transportation Research Council
Benjamin H Cottrell, Jr., Virginia Transportation Research Council
The recent widespread application of the flashing yellow arrow (FYA) provides the opportunity to vary left-turn phasing mode by time of day. There is therefore a need for tools that predict how the risk for left-turn crashes might vary at a more disaggregated level (e.g. hourly) than that provided by existing crash prediction models, which typically predict annual totals of left-turn crashes, often based on average daily traffic volumes. The use of traffic simulation to analyze complex transportation issues has become common practice in transportation engineering. The further application of microsimulation to the analysis of traffic safety in a systematic, rigorous, and controlled fashion is becoming increasingly viable as simulation models improve and tools for quantifying surrogate safety measures become readily accessible. Using a calibrated VISSIM traffic microsimulation model and surrogate safety assessment model (SSAM) analysis, this paper examined how the risk for left-turn crashes varied as traffic conditions changed at a signalized intersection. Safety impacts for 750 unique combinations of intersection geometry, traffic, and signal timing parameters were simulated and the number of left-turn conflicts per hour noted. Results of the simulation analyses were used to develop statistical models that expressed the risk of occurrence of a left-turn crash during a given hour as a function of the left-turn phasing mode and prevailing conditions during that hour. Potential application of the model to the implementation of a time-variable safety-based left-turn phasing selection scheme using FYA was successfully demonstrated.
Evaluating Drivers’ Stop-Line Violation Behavior at Signalized Intersections
Martin Pietrucha, Pennsylvania State UniversityShow Abstract
Xinyu Zhou, IQVIA
Vikash Gayah, Pennsylvania State University
Eric Donnell, Pennsylvania State University
Stop lines are common at intersections; however, few studies have focused on the position of stopped vehicles with respect to the stop line. Often drivers will stop their vehicles over the line creating potential operational or safety problems. In this paper, data collected from local intersections in State College, Pennsylvania, indicated that only 61 percent of the vehicles observed were in compliance and 13 percent of the vehicles observed were committing severe violations. The data were analyzed to characterize driver behavior related to stop location during red phases. Driver stop line violations were influenced by many factors in this study. Lane usage (right turn only) was associated with high violation rates. Minor roads, when compared to major roads, were more likely to have more severe violations, while morning periods had more minor violations than other time periods. Through only lanes or increased distance from the stop line to the crosswalk or curb extension line promoted higher rates of compliance. Improving sight lines and maintaining sufficient sight distance and vehicle stopping distance could cut down on the problem. Increasing the distance from a stop line to a crosswalk or curb extension line an additional 10 feet might provide enough space for the majority of the vehicles stopping at an intersection from entering the crosswalk or intersection area.
Analysis and Real-Time Implementation of Variable Advisory Speed Limit Messaging During Winter Storms
Shefang Wang, Iowa State UniversityShow Abstract
Anuj Sharma, Iowa State University
Skylar Knickerbocker, Iowa State University
Neal Hawkins, Iowa State University
The goal of a variable advisory speed limit system is to provide reliable, realistic, and real-time speed limit information to roadway users. Four dynamic advisory messaging systems were evaluated along the southbound Interstate 35 corridor between the communities of Huxley and Ankeny, Iowa. The advisory system is currently operating in background mode without display messages, which allows researchers to verify the accuracy of the messages before being deployed to the public. The existing variable advisory messaging logic was based on nearby speed sensors with a set of fixed threholds of speed; however, its performance was found to be less than desirable during snow events. The goal of this study was to develop new advisory speed limit logic using radar-based sensors to minimize the number of short duration and fluctuating messages. This proposed logic uses a wavelet transform to remove noisy sensor measurements and applies K-Mean clustering to find a reasonable number of message groups. In this case, these clustered groups were then labeled by traffic engineering experts and a classification tree was used to replicate the experts’ engineering judgment. The new advisory logic was evaluated in ghost mode based on real-time sensor inputs during winter snow events.
Traffic Sign Design with Inkscape and OpenSignTool: An Open Source Approach
George Zhang, Virginia Department of TransportationShow Abstract
This paper documents an effort to develop a sign design software package OpenSignTool for open source vector graphic drawing software Inkscape. The OpenSignTool consists of several Python extension programs. The paper describes the general procedure of designing a traffic sign with Inkscape and OpenSignTool. The Draw Border tool is for creating the sign border, and the Place message Line tool is for creating sign messages. Auxiliary lines for alignment are drawn with the Place Alignment Lines tool. The design of OpenSignTool closely follows the sign design standards. In areas where the standard is not clear, the details of the software implementation are discussed in this paper. The tool was utilized to create a sign poster containing 673 commonly used standard signs. It provides a new approach for professionals and hobbyists to design signs and get involved in the open source software.
Closed-Course Examination of Raised Retroreflective Pavement Markers Impact on Speed Change and Braking Behavior in Small Radius Curves
Timothy Barrette, Texas A&M Transportation InstituteShow Abstract
Adam Pike, Texas A&M Transportation Institute
Operational studies on raised retroreflective pavement markers (RRPMs) have largely focused on observational field studies of driver behavior and surrogate safety measures. While these studies are important, they fail to capture driver behavior in a continuous fashion, often focusing on discrete points along an analysis segment. Instrumented vehicles provide a valuable tool for transportation research by providing researchers data on a continuous basis. Insight into vehicle performance characteristics that would not be available to field researchers, such as brake force and brake application can be collected using onboard computers. Additionally, characteristics such as vehicle speed can be observed at much higher frequencies, providing a more complete picture of driver behavior. This paper makes use of the three aforementioned performance metrics to quantify driver behavior in small radius curves in the presence of RRPMs. Graphical analyses of maximum brake force, distance from curve at maximum brake application, and speed loss in curve were conducted to provide high-level insight into the nature of the data. The graphical analysis was followed with a statistical analysis on distance from the curve at maximum brake application and speed loss. These analyses demonstrate several important characteristics of driver behavior when RRPMs are used: first, maximum braking occurs further from the curve as the retroreflectivity of the RRPMs in the curve increase, and second, that the magnitude of speed change in the curve decreases as the retroreflectivity of the RRPMs increase. This research is ultimately useful in providing a framework to develop minimum RRPM performance criteria.
Evaluation of Audible Lane Departure Warning Treatments
Adam Pike, Texas A&M Transportation InstituteShow Abstract
Bryan Wilson, Texas A&M Transportation Institute
To help reduce single vehicle run-off-road and two-lane two-way crossover crashes, TxDOT has implemented various audible lane departure warning systems on seal coat road surfaces. This 20-month research project explored the effectiveness of these treatments using interior noise and vibration performance metrics and provided recommendations on implementation of these types of treatments. The researchers conducted performance evaluations at 24 unique field sites that had 51 treatments, and at a test deck that had 12 different variations of audible markings. The field sites consisted of varying designs and spacing of audible markings, varying spacing of rumble bars, and milled rumble strips. Researchers found that treatment effectiveness varies with vehicle type and vehicle speed. Traveling at higher speeds and in a vehicle with a stiffer suspension results in higher noise and vibration levels. The specific treatment design also impacts the performance. Treatments with closer spacing, longer bumps, and higher profiles produced higher noise and vibration levels. Certain alternative treatments were able to produce noise and vibration levels that approached levels of typical milled rumble strips. In areas where milled rumble strips cannot be used, these alternative treatments are viable options.
Closed-Course Assessment of Driver Lane-Keeping Behavior Through Small-Radius Curves in the Presence of RRPMS
Emira Rista, Texas A&M Transportation InstituteShow Abstract
Timothy Barrette, Texas A&M Transportation Institute
Adam Pike, Texas A&M Transportation Institute
Surrogate safety measures, which may more accurately described as quantification of erroneous vehicle operations, are frequently used to capture the effect of RRPM installations. Two of the most commonly used include lateral position and encroachment frequency. Using vehicle position tracked via a centrally mounted GPS antenna, severe encroachment (vehicle GPS antenna directly at or beyond the centerline) were tabulated form the study data. A logistic regression model was estimated to assess the role of RRPM retroreflectivity and driver characteristics on encroachment probability. This study methodology provides insight into whether lateral position is a good surrogate safety metric. When studied in the field, lateral position is often represented in terms of mean and variance at specific points of an analysis segment; however, this approach is unable to account for the change in lateral position of individual vehicles within a segment and subsequently does not capture a potentially critical indication of visibility and safety. Using an instrumented vehicle and a closed course study design, this research investigates the visibility of RRPMs in small-radius curves on the basis of absolute position change, i.e., the absolute change in position relative to the lateral position of the vehicle at the point of curvature. Regression analysis was used to relate RRPM retroreflectivity to changes in lateral position. Driver performance in terms of encroachment and magnitude of change in lateral position were shown to improve with the presence of RRPMs and as RRPM retroreflectivity increased.
Impacts of Freeway Speed Limit on Operation Speed of Adjacent Arterial Roads
Fadi Alhomaidat, Western Michigan UniversityShow Abstract
Valerian Kwigizile, Western Michigan University
Jun-Seok Oh, Western Michigan University
The speed limit is one of the essential factors associated with roadway safety. The spillover effect is the tendency of drivers to drive at a higher speed on non-freeway roadways after exiting the freeway. Speed studies were conducted on urban arterial roads with speed limits of 45 mph. These roads are adjacent to freeways where the speed limit had been raised from 55 to 70 mph. Comparison of speed differences between motorists who exited the freeway and those who were already driving on the arterial road was performed. Results showed that with the increase in the speed limit from 55 mph to 70 mph, the mean speed and the 85th percentile speed of passenger cars exiting from the 70 mph freeway increased significantly when compared to those exiting from the 55 mph freeway. Differences in the mean speeds between vehicles exiting from freeways and vehicles already driving on the arterial road were observed at the two sites. This paper provides researchers, policymakers, and engineers with a better understanding of the effects of speed spillover on adjacent roads when determining whether to increase the speed limit on freeways.
Traffic Control Devices for Deterring Wrong-Way Movements at Unsignalized Intersections on Divided Highways
Melisa Finley, Texas A&M Transportation InstituteShow Abstract
Raul Avelar, Texas A&M Transportation Institute
Gene Hawkins, Texas A&M University
Motorists driving the wrong way on divided roadways has been an area of concern for over 50 years. However, little is known about the nature of wrong-way crashes on divided highways. Thus, researchers conducted exploratory and statistical analyses to assess the effects of median width and select traffic control devices upon wrong-way crashes on high-speed divided highways. The exploratory analysis revealed that most of the wrong-way crashes on high-speed divided highways resulted in serious injury and happened at night. More than two-thirds of the wrong-way crashes resulted from a wrong-way maneuver at an intersecting roadway where a median opening was present. The statistical analysis found numerous sites where the traffic control in the median opening did not fully comply with the Manual on Uniform Traffic Control Devices (MUTCD) with respect to treating the location as one or two intersections. There was also evidence from the statistical analysis that the 30-ft median width threshold may not be appropriate for distinguishing between one or two intersections. In addition, researchers were able to identify several traffic control devices that may be effective in reducing wrong-way movements on high-speed divided highways. The final effort of the project was to develop recommended MUTCD language for implementing the research findings. The recommended language includes a new method for distinguishing between divided highway crossings that function as a single intersection or two separate intersections; thereby eliminating the 30-ft median width threshold used in the current MUTCD.
How Should the Pattern of Speed Reduction Markings Vary According to Curve Radius?: Evidence from Field Experiments in Japan
Hirofumi Yotsutsuji, CERI of HokkaidoShow Abstract
Jian Xing, Nippon Expressway Research Institute
Hideyuki Kita, Kobe University
Keiichiro Yonemura, Katahira & Engineers, Inc.
Hodaka Kai, Nippon Expressway Research Institute
Takahide Matsumoto, Katahira & Engineers, Inc.
This study focuses on the effective pattern of spacing between marking lines of speed reduction markings (SRMs) installed on straight lane adjacent to transition curve section, in order to induce vehicles to reduce their speed safely before entering the curve. The aim of this study is to show evidence of how the spacing pattern of SRMs should vary according to the curve radius, considering a change in curve radius affecting the vehicle speed in the absence of SRMs, based on causal inference with a difference-in-differences method incorporating an instrumental variable method using field experiment data. Our findings are summarized as follows: In the case of relatively small radius of curvature (300 m in this study), the effect of pattern End, which is corresponding to the pattern of spacing with greater decrease ratio (DR) between the lines in end section than in beginning section on the SRM-installed lane, is higher than the effect of pattern Beginning for drivers who are driving at the speed of about 90 to 100 km/h or at about 100 to 110 km/h. In the case of relatively large radius of curvature (600 m in this study), the effect does not significantly differ between pattern End and pattern Beginning for the drivers. Consideration on the spacing pattern of SRMs may be useful in the case of the vehicles moving toward the curve at a velocity different from the design speed corresponding to an advisable minimum radius of the curve.
Developing and Implementing MUTCD Criteria for Selecting Traffic Control for Unsignalized Intersections
Gene Hawkins, Texas A&M UniversityShow Abstract
Kay Fitzpatrick, Texas A&M Transportation Institute
Marcus Brewer, Texas A&M Transportation Institute
The 2009 Manual on Uniform Traffic Control Devices includes guidance for the use of various types of traffic control at unsignalized intersections. Despite changes and advances in traffic engineering in recent decades, the MUTCD content related to selection of traffic control in Part 2B has seen only minor changes since 1971. The types of unsignalized traffic control addressed in this research included no control, yield control, two-way stop control, and all-way stop control. The research team developed recommendations using information available from reviews of existing literature, policies, guidelines, and findings from an economic analysis along with the engineering judgment of the research team and panel. The researchers then developed recommended language for the next edition of the MUTCD for unsignalized intersections. It includes consideration of high-speed (rural) and low-speed (urban) conditions along with the number of legs at the intersection. Because the number of expected crashes at an intersection is a function of the number of legs, the decision on appropriate traffic control should also be sensitive to the number of legs present. The proposed language includes introductory general considerations, discusses alternatives to changing right-of-way control, and steps through the various forms of unsignalized control from least restrictive to most restrictive, beginning with no control and concluding with all-way stop control.
Improvements on Road Marking Design to Enhance the Effectiveness of Semiautonomous Vehicles
García Alfredo, Universitat Politècnica de ValènciaShow Abstract
Francisco Javier Camacho-Torregrosa, Universitat Politècnica de València
Increasing existence of semi-autonomous vehicles makes it necessary to analyze their interaction with road marking design. Current systems present digital image processing technology that reads the oncoming road path and process the information. However, road markings were designed to be interpreted by drivers, not vehicles. Thus, the semi-autonomous systems sometimes may misinterpret this information, if it is confusing or inconsistent for the system. Several observations along freeways have been performed. The semi-autonomous system tends to fail at entrance or exit ramps, where no extension edge lines are set. Additional road layouts, such as lane reduction or addition, road merging or split, also create zones with no road markings that are not correctly read by the system. Some proposals are recommended to address this situation, based on observations and revision of guidelines of other countries. The suggested proposals are very inexpensive to implement and would not be misinterpreted by drivers.
Safety Impact of Edge Lines Wider Pavement Marking
Mohamed Mohamed, University of IdahoShow Abstract
Maged Mohamed, University of Idaho
Ahmed Abdel-Rahim, University of Idaho
Kevin Chang, University of Idaho
The primary role of pavement markings is to provide a visual cue to drivers to assist them with vehicle position along a roadway and help them make a proper lane change decision. For this study, the objective was to determine the safety effectiveness of wider pavement markings with regard to traffic safety. Before and after studies using comparison group and Empirical Bayes methods were applied using crash data from thirty-eight independent two-lane rural highway locations in the state of Idaho to determine that if there was a relationship between the implementation of wider pavement markings and vehicle crashes. Safety performance functions (SPF) for run-of-the-road crashes (ROR) in Idaho for two-lane rural highways were also developed. This study concluded that there is a strong relationship between wider pavement marking width and a reduced number of ROR crashes particularly those involving fatal and serious injuries crashes. The research results showed that wider pavement marking implementation has the potential to reduce fatal and serious ROR crashes by 10.1 percent with an expected cost to benefit ratio of approximately 1:25. For this reason, the implementation of wider pavement marking widths by agencies along two-lane rural highways is encouraged to provide a long-term safety benefit for the motoring public.
North Carolina's Zipper Merge Experience
Christopher Vaughan, Institute for Transportation Research and EducationShow Abstract
Christopher Cunningham, North Carolina State University
Sarah Searcy, North Carolina State University
Chris Carnes, North Carolina State University
Daniel Coble, Institute for Transportation Research and Education (ITRE)
The Institute for Transportation Research and Education (ITRE) at North Carolina State University conducted a study for the North Carolina Department of Transportation (NCDOT) observing zipper merges on roadways for effects on merging behavior in order to improve travel times. The zipper merge was implemented at three sites across central and eastern North Carolina: 1) a permanent rural arterial two-to-one lane drop, 2) a suburban freeway permanent three-to-two lane drop, and 3) a rural freeway two-to-one temporary lane drop inside of a work zone. Lane utilization was not proven to be greatly affected by the zipper merge treatment; the greatest increase in the closing lane’s utilization at any site was five percent. The lack of change in lane utilization is likely due to sign misunderstanding. Overall, travel times at the sites decreased modestly, with some minor increases during certain time periods. The increases may be due to outside factors such as crashes, but the actual cause is unknown. The most significant decrease in travel time occurred at the work zone site. This location utilized a dynamic zipper merge setup and experienced a one minute decrease in travel time, which equates to an 11 mile per hour increase in space mean speed. Safety was the biggest improvement observed. Far fewer vehicles entered the shoulder at the taper while merging after implementation of the zipper merge.
Red Light Violation Identification Using GPS Trajectories
Melrose Pan, University of ArizonaShow Abstract
Xiaofeng Li, University of Arizona
Robert Kluger, University of Louisville
Yao-Jan Wu, University of Arizona
Red-light violations often result in serious crashes. However, few monitoring systems are in place for system operators to monitor their occurrence. This paper successfully uses crowd-sourced GPS-based vehicle trajectories, combined with high-resolution traffic signal event-based data, to identify instances of red-light violations. Red light violations are defined based on the nature of the violation in relation to the signal phase. A detailed framework is proposed to combine temporal and spatial, GPS data and signal timing data and classify different movement behaviors through intersections as they relate to the red phase. The GPS data cleaning and processing procedures are presented in the context of the framework developed. With the proposed method, different patterns of RLVs are identified in a case study in Tucson, Arizona during the morning peak hours over December, 2017. The results were consistent with the body of knowledge and expectations associated with RLVs.
Learning Speed Limit Signs for Ramps from OEM Sensor Data: An Autonomous Vehicle Application
Leon Stenneth, HERE TechnologiesShow Abstract
Zaba Sebastian, HERE Technologies
Zhenhua Zhang, HERE Technologies
Traffic sign recognition (TSR) plays a vital role in autonomous driving in recent years. Autonomous vehicles can adjust their cruise speed using the sign information learned by the TSR system. However, sometimes, the commercial TSR systems may be inaccurate near the ramps due to that: (1) The TSR systems usually are not as advanced as those state-of-the-art systems under the experimental settings and there may be misclassification. (2) There may be partial occlusion of the speed limit signs under certain conditions. (3) The complex road networks have negative impact on the TSR quality. Problems happen mostly near ramps where vehicles running on the main link can detect the signs on the ramps which will result in an unexpected speed reduction. Instead of improving the algorithm or increasing the system reliability, this paper proposes a new way to counter TSR problems near ramps. A pipeline is proposed to derive the correct speed limit information near ramps. In this pipeline, the TSR observations from multiple vehicles are first clustered by Layered-DBSCAN, then loaded on the map links and finally adjusted to the correct links using both TSR features and road geometry features. Our testing results show that signs after the pipeline can greatly increase the accuracy of sign detection and overcome the problems of misclassification and wrong-detection.
Evaluating the Safety Impact of Flashing Red Arrow Protected Permissive Left Turn Signal Control in Maryland
Ranteg Singh Rao, University of MarylandShow Abstract
Piotr Rachtan, Maryland State Highway Administration
Gang-Len Chang, University of Maryland, College Park
Maryland has used flashing red arrow (FRA) since the 1980’s at intersections operated with protected-permissive left-turn (PPLT) control, but impacts of this display on traffic safety have yet to be rigorously assessed. To evaluate the safety impacts of FRA and develop reliable guidelines this study has used data from 23 intersections in Maryland where the PPLT display was converted from a five-section (doghouse) cluster signal head with circular green to a three-section signal head with FRA and a supplemental sign. Safety Performance Functions (SPFs) calibrated for Maryland are developed on a sample of 20 intersections using PPLT display with circular green. Using the Empirical Bayes (EB) method, the results from the safety evaluation of FRA show that the respective crash modification factors (CMF) for left-turn crashes and total crashes were 0.53 and 0.75, thereby showing that FRA signals for PPLT control increase the safety at signalized intersections. Similarly, the CMFs for left-turn and total crashes resulting in injuries were found to be 0.63 and 0.71 respectively. Overall, among the 23 intersections, the left-turn crashes decrease by as much as 87%, and similar patterns were also observed for left-turn crashes resulting in injuries.
An Evaluation of Low-Cost Countermeasures for Preventing Wrong-Way Driving Incidents Based on Two Before-and-After Case Studies
Qing Chang, Auburn UniversityShow Abstract
Md Atiquzzaman, Auburn University
Huaguo Zhou, Auburn University
In this study, before-and-after analyses were conducted at two exit-ramp terminals of partial cloverleaf interchanges (I-65 Exit 284 and I-65 Exit 208) in Alabama. Based on a previous research project, these two locations were identified as high-risk locations for Wrong-Way Driving (WWD) having more than 10 WWD incidents at each during a typical weekend. Alabama Department of Transportation (ALDOT) regional engineers have implemented some low-cost countermeasures to mitigate the WWD activities at these two locations. At I-65 Exit 284, the pavement marking was improved, including (1) new double yellow line and left-turn skip strips on the crossroad, and (2) yield line for right turn lane and stop bar for left turn lane at end of the exit ramp. At I-65 Exit 208, raised-curb channelized island was implemented to reduce the width of exit ramp. There has little document on the effectiveness of these types of low-cost countermeasures in reducing WWD incidents. In this study, the WWD incident data were collected at these two locations before and after the countermeasures were implemented. At I-65 Exit 284, the implemented countermeasures reduced 65% of the total and approximately 89% of nighttime WWD incidents. The study found that drivers follow more closely to left-turn skip strips during nighttime than the daytime. However, at I-65 Exit 208, implemented channelized island resulted in approximately 80% increase in WWD incidents. Additional signage and pavement markings need to be improved along with the channelized island to achieve better effectiveness in preventing WWD incidents at this location.
Leading Through Intervals Versus Leading Pedestrian Intervals: More Protection with Less Capacity Impact
Peter Furth, Northeastern UniversityShow Abstract
Ray (Mohammad) Saeidi Razavi, Northeastern University
When pedestrian and/or bike crossings are concurrent with a vehicular phase, leading through intervals (LTI) and leading pedestrian intervals (LPI) are signalization techniques that provide a partially protected crossing. With an LPI, for a short interval at the start of the crossing phase, all traffic is held, enabling some pedestrians to arrive at the conflict zone and thus reinforce their priority before turning vehicles are released. An LTI functions similarly, except that during the leading interval, only turning traffic is held; through traffic is allowed to run. This lessens the negative capacity impact compared to LPI, and consequently allows LTI to have a longer leading interval, thus affording pedestrians and bikes greater protection. Montreal’s and New York’s experience with LTIs is reviewed. A model is developed to estimate capacity loss from using LPI and LTI for a range of scenarios in which right turns share a lane with through traffic, in which case an LTI can indirectly block through vehicles positioned behind a turning vehicle. While LTI’s capacity loss increases with the proportion of right turns, for the wide range of right turn proportions tested, it is still far lower than the capacity loss for an LPI of the same length, especially on multilane approaches.
Operational Evaluation of Do Not Block the Box Campaigns
Abhilasha Saroj, Georgia Institute of Technology (Georgia Tech)Show Abstract
Nishu Choudhary, Georgia Institute of Technology (Georgia Tech)
Han Gyol Kim, Georgia Institute of Technology (Georgia Tech)
Samuel Harris, Georgia Institute of Technology (Georgia Tech)
Angshuman Guin, Georgia Institute of Technology (Georgia Tech)
Michael Rodgers, Georgia Institute of Technology (Georgia Tech)
Michael Hunter, Georgia Institute of Technology (Georgia Tech)
In congestion, when a vehicle enters an intersection with insufficient space to exit on the opposite side due to downstream traffic spillback, it often leads to the obstruction of vehicle and pedestrian movement on conflicting approaches. This “blocking the box” can propagate to nearby intersections with negative traffic impacts such as capacity reductions and increased travel times and, in extreme cases, can lead to gridlock. This paper investigates the effectiveness of “Don’t Block the Box” (DBTB) treatments in minimizing driver’s blocking an intersection. This research explores the performance of DBTB treatments by: 1) conducting a “before-after” DBTB treatment comparison study at six intersections in Atlanta, Georgia and by 2) quantifying the impact of vehicle blocking behavior on intersection performance using a microscopic simulation model. The study results indicate that the DBTB treatment installation did not significantly improve the likelihood that drivers would not choose to “block the box” when provided with an opportunity to do so. Importantly, even where the likelihood a driver would choose to block did decrease after the DBTB treatment installation the rate of blocking remained high, with more vehicles likely to block than not (i.e. posterior blocking propensities >50% at all sites). In addition, regardless of the presence of DBTB treatments, from the simulation it was seen that the rate at which drivers chose to block has the potential to significantly increase congestion and vehicle delay. However, it was also seen that if the effectiveness of the treatment could be improved significant benefits could be achieved.
Evaluation of Driver Comprehension and Visual Attention of the Flashing Yellow Arrow Display for Permissive Right Turns
Hisham Jashami, Oregon State UniversityShow Abstract
David S. Hurwitz, Oregon State University
Christopher Monsere, Portland State University
Sirisha Kothuri, Portland State University
This research explored driver comprehension and behaviors with respect to right-turn signal displays focusing on the Flashing Yellow Arrow (FYA) in a driving simulator. A counter-balanced, factorial design was chosen to explore three independent variables: signal indication type and active display, length of the right-turn bay, and presence of pedestrians. Driver decision making and visual attention were considered. Data were obtained from 46 participants (21 women) turning right 736 times in 16 experimental scenarios. A Mixed-effects Ordered Probit Model and a Linear mixed model were used to examine the influence of driver demographics on observed performance. Results suggest that the FYA indication improves driver comprehension and behavioral responses to the permissive right-turn condition. When presented with the FYA indication in the presence of pedestrians, nearly all drivers exhibited caution while turning and yielding to pedestrians and stopping when necessary. For the same turning maneuver, drivers presented with a Circular Green indication were less likely to exhibit correct behavior. At least for Oregon drivers, another clear finding was a general lack of understanding of the steady red arrow display for right-turns. Most drivers assume the SRA indication requires a different response than the Circular Red and remain stopped during the entire red interval, thus resulting in efficiency losses. These findings suggest that transportation agencies could potentially improve driver yielding behavior and pedestrian safety at signalized intersections with high volumes of permissive right turns from exclusive right-turn lanes by using the FYA display in lieu of a steady circular green display.