Uniform Traffic Control Devices Research Articles

Traffic Sign Retroreflectivity Condition Assessment and Deterioration Analysis Using Lidar Technology

Traffic sign retroreflectivity is critical for nighttime visibility, an important factor in driver safety. Current methods of sign retroreflectivity assessment are expensive, time-consuming, dangerous, or subjective. There is an urgent need to explore an alternative method that is cost-effective, safe, objective, and can be operated during daytime or nighttime. One such method is mobile lidar. However, a methodology utilizing lidar cloud data for practical retroreflectivity condition assessment is still lacking because of the inability to numerically correlate lidar retro-intensity readings to the retroreflectivity standard set by the Manual on Uniform Traffic Control Devices (MUTCD). In addition, there is also a need to explore sign deterioration behavior using real-world lidar data. In this study, we (1) propose a practical, categorical traffic sign condition assessment using lidar data; (2) establish a preliminary correlation between the retro-intensity and retroreflectivity readings to determine the minimum retro-intensity thresholds for condition assessment of different sheeting types and colors; (3) validate the accuracy of the assessment by comparing it with standard nighttime visual inspection outcomes; (4) demonstrate the practical implementation through a feasibility study at Georgia Interstate 285; and (5) reveal the retro-intensity deterioration trends using historical lidar cloud data. The results show that the proposed methodology can reliably yield results comparable to manual measurements, potentially reducing sign retroreflectivity condition assessment effort, increasing the transportation agency’s productivity, and filling gaps where manual assessment is not possible. Additionally, the retro-intensity deterioration trends can help transportation agencies to understand the long-term behavior of sign retro-intensity and predict the optimal timing for sign replacement.

Conspicuity of Various Colored Express Lane Delineators: Matching or Contrast?

Express lanes (ELs) are an increasingly accepted traffic management tool for congestion relief and traffic efficiency. White, yellow, and orange vertical delineators are typically used for lane separation and channelization applications. However, upcoming changes to sections of the Manual on Uniform Traffic Control Devices that would affect the current use of the orange retroreflective delineators will have a statewide impact on current and future ELs. The availability of a wide array of delineator colors and the potential range of application purposes brings into question this blanket requirement. The ineffective use of color in roadway design could lead to an increase in driving errors/response time, driver fatigue, loss of situational awareness, and increased workload. Driver perception and reaction time is shown to be affected by visual factors, such as color, luminance, distractions, and speed. The objective of this study is to determine the impact of color usage and other environmental and demographic factors on driver perception. A fractional factorial experiment was designed to study the EL delineator color selection using a driving simulator and an eye-tracking device. The potential factors included time of day (night versus day), visibility (high versus low), traffic density (high versus low), and road surface type (concrete versus asphalt). Some 176 subjects were selected to participate in the experiment. It was found that, in general, white was the quickest to be noticed, while black took the longest time to perceive. Furthermore, it was found that delineators were generally more noticeable under night-time conditions, likely because of the standard use of retroreflective striping on delineators.

Sign Life Expectancy on Low-Volume Roads in Iowa

Traffic signs provide warning and guidance information to drivers 24 h a day. They also represent a significant maintenance and replacement concern and cost for agencies with the advent of retroreflectivity requirements. In some cases, agencies choose to replace their signs in conjunction with the end of the manufacturer warranty period or other time intervals to maintain sign retroreflectivity. However, this could result in signs being replaced while they still exceed their minimum retroreflectivity requirements, with labor and material costs being incurred years before necessary. This research evaluated retroreflectivity data from in-service signs in Iowa, U.S., to determine expected sign life values. It evaluated 10,799 retroreflectivity data points across three different sheeting materials for a variety of sign types. A total of 65 linear regression models were developed to evaluate signs by sheeting type, age, and sign category (regulatory, warning, and guide), as well as directional orientation. The results indicated that all sheeting materials, sign types, and sign directions were predicted to have lives of at least 10 years before falling below Manual on Uniform Traffic Control Devices (MUTCD) minimums. Plots of retroreflectivity versus age indicated that many signs remained well above the MUTCD minimums at the predicted age where failure was expected. In general, the predicted lives for a material/sign type/direction combination were greater than 5 years longer than manufacturer warranty periods. For conservative purposes, agencies could consider a sign to be approaching minimum retroreflectivity levels at approximately 5 years past the manufacturer warranty, based on the research results.

Incident Duration Time Prediction Using Supervised Topic Modeling Method

Accurate prediction of the duration of traffic incidents is one of the most prominent prerequisites for effective implementation of proactive traffic incident management strategies. This paper presents a novel method for immediate prediction of traffic incident duration using an emerging supervised topic modeling. The proposed method employs natural language processing techniques for semantic text analysis of the text-based incident traffic incident dataset. The model applies the labeled latent Dirichlet allocation approach, and it is trained using 1,466 incident records collected by the Korea Expressway Corporation from 2016 to 2019. For training purposes, the proposed method divides the incidents into two groups based on the incident duration: incidents shorter than 2 h and incidents lasting 2 h or longer, following the incident management guidelines of the Federal Highway Administration Manual on Uniform Traffic Control Devices for Streets and Highways (2009). The model is tested with randomly selected incident records that were not used for the model training. The results demonstrate overall prediction accuracies of approximately 74% for incidents lasting up to 2 h, and 82% for incidents lasting 2 h or longer.

Pavement Marking Practices, Standards, Applications, and Retroreflectivity

Pavement markings are important elements of roadway networks and help guide traffic flow in an orderly manner. In recent years, transportation agencies are facing challenges to manage pavement markings because of the advent of new vehicle technologies. Existing pavement marking standards were developed for serving human road users but they may not be effective for both human drivers and machine vision systems. Therefore, the National Committee on Uniform Traffic Control Devices suggested amendments to the current pavement marking standards. Therefore, it is necessary to explore pavement marking practices for a variety of states. With this aim, the Wyoming Technology Transfer Center conducted an online survey as part of a comprehensive research project on developing pavement marking management plans for the Wyoming Department of Transportation. The main objective of the survey is to document the various state Departments of Transportation (DOTs’) pavement marking management plans, how the plans are developed, strategies for pavement marking data collection, and pavement marking retroreflectivity. The survey has 31 questions dealing with pavement marking striping, pavement marking data collection, pavement marking retroreflectivity, and a few miscellaneous questions. There are 29 DOTs who responded to the survey. This paper summarizes the responses from the survey on evaluating pavement marking management practices at a national level.

Improved Practices for Temporary Work Zone Guide Signs

Freeway reconstruction projects often involve adding lanes and improving entrance and exit ramps. Sign supports for overhead guide signs are sometimes removed early in the project to make way for construction activities. In addition, roadside guide signs may need to be relocated and replaced with temporary guide signs. The Manual on Uniform Traffic Control Devices provides guidance for work zone guide signs in Part 6, stating that temporary guide signs shall have black legend and border on an orange background. But permanent guide signs follow Part 2 of the MUTCD, which prescribes white legend and border on a green background for guide signs in general. Thus, many long-term freeway work zones may have guide signs in both color schemes that change throughout the project as the construction work progresses. The constrained conditions often seen in these work zones can also result in guide signs that use a variety of fonts, font sizes, sign sizes, and placement positions. This paper describes the human factors study that was performed to assess motorist understanding of various work zone guide signage strategies. Based on the results, the researchers were able to develop recommendations for long-term work zone guide sign design and placement to improve uniformity for the traveling public.

Developing Efficiency Attributes for Right-Turn Flashing Yellow Arrow on Impeding through and Opposing Left Phases Using a Multinomial Logit Model

AbstractThe right-turn flashing yellow arrow (FYA) signal display is still considered a new signal practice in the United States. The Manual on Uniform Traffic Control Devices (MUTCD; 2009) allocat...

Effect of Changing a Traffic Control Device Color on Driver Behavior and Perception across Different Age Groups

The use of express lanes (ELs) in freeway traffic management has seen increasing popularity throughout the United States, particularly in Florida. These lanes aim at making the most efficient transportation system management and operations tool to provide a more reliable trip. An important component of ELs is the channelizing devices used to delineate the separation between the ELs and the general-purpose lane. With the upcoming changes to the FHWA Manual on Uniform Traffic Control Devices, this study provided an opportunity to recommend changes affecting safety and efficiency on a nationwide level. It was important to understand the impacts on driver perception and performance in response to the color of the EL delineators. It was also valuable to understand the differences between demographics in responding to delineator colors under different driving conditions. The driving simulator was used to test the responses of several demographic groups to changes in marker color and driving conditions. Furthermore, participants were tested for several factors relevant to driving performance including visual and subjective responses to the changes in colors and driving conditions. Impacts on driver perception were observed via eye-tracking technology with changes to time of day, visibility, traffic density, roadway surface type, and, crucially, color of the delineating devices. The analyses concluded that white was the optimal and most significant color for notice of delineators across the majority of subjective and performance measures, followed by yellow, with black being the least desirable.

Estimating passing sight distances for overtaking truck platoons – Calibration and validation using VISSIM

Two-lane highways comprise a substantial proportion of the nation’s highways. One of their critical aspects is the passing sight distance (PSD), which is the minimum distance required for executing a safe passing maneuver using the opposing travel lane. Sight distances that are shorter than the available PSD warrant the designation of no-passing zones. The PSDs, documented in the Manual on Uniform Traffic Control Devices, are developed based on the premise that only one slower moving impeding vehicle is being overtaken. Yet, the oil and gas industry in Wyoming advises its truck drivers to travel in platoons creating a complicated situation for trailing vehicles. Passing a single impeding vehicle is cumbersome, not to mention passing multiple trucks. The PSD is augmented by the length of each truck in the platoon and the spacing among the trucks. In this research, an existing mathematical kinematics PSD model is implemented to compute the PSDs needed to pass multiple oil and gas trucks for a variety of scenarios belonging to two-lane highway segments with posted speed limits of 70 mph. The PSDs computed range from 1385 to 1915 ft depending on the number of trucks in the platoon and spacings between the trucks. The results are compared with those of VISSIM microsimulation models, which are validated using field traffic volume data. The discrepancies between the computed PSD results and those of the simulations are less than 3%. Furthermore, it is recommended to deploy passing lanes to mitigate the effects of truck platoons on traffic operations.

Public Comment on Proposed Revisions to the Manual on Uniform Traffic Control Devices for Streets and Highways - Proposed Rule; Notice of Proposed Amendments to National Standards for Traffic Control Devices: Manual on Uniform Traffic Control Devices for Streets And Highways; Revision Docket Id: Fhwa-2020-0001 Regulation Identifier Number (Rin) 2125-Af85

This comment was submitted in response to a Notice of Proposed Amendments to the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD establishes national standards for certain aspects of road design and transportation policy. Our comment calls upon the MUTCD's owner, the Federal Highway Administration, to scrap the current review process and conduct a full rewrite of the MUTCD. We also call upon the FHWA to exercise its authority under the Administrative Procedure Act to issue an emergency rule withdrawing a method it sanctions for modifying speed limits, the 85th Percentile Method.

Analysis of Pedestrian Hybrid Beacon Operation on Higher-Speed Roadways

The pedestrian hybrid beacon (PHB) is a traffic control device used at pedestrian crossings. It was first included in the 2009 Manual on Uniform Traffic Control Devices and was based on the HAWK developed in Tucson, Arizona. The focus of an Arizona Department of Transportation research study was the investigation of the use of PHBs on higher-speed roads. Ten locations in Arizona representing higher operating speed conditions (85th percentile speed ranging from 44 to 54 mph) were selected for inclusion in this study. Data were collected using a multiple video camera setup. The final dataset reflected about 40 h of video data and included 1,214 pedestrians or cyclists crossing at PHBs. Overall, driver yielding for these 10 sites averaged 97%, which is similar to driver-yielding rates for PHBs installed on lower-speed streets.

ARTS: Automotive Repository of Traffic Signs for the United States

Traffic signs recognition (TSR) is a crucial sub-domain of computer vision, particularly relevant to autonomous vehicles and autonomous driver-assistance systems (ADAS). TSR systems can further augment efforts in many other applications, such as highway asset maintenance and management. Despite the relative success of detectors with hand-crafted features in Europe, most, if not all, non-deep-learning based systems are not scalable to accurately recognize a large subset of traffic signs in the United States. The recent works in the domain of object detection using machine learning have shown the necessity of deep neural networks (DNNs) in TSR, whereby a DNN can learn features automatically without hand-crafting them. Due to the lack of datasets in the U.S. and the inefficient use of traditional methods for traffic sign recognition (TSR) in the U.S., we created the Automotive Repository of Traffic Signs (ARTS), a new dataset for traffic signs recognition in the U.S. ARTS covers a wide range of sign-types, including Regulatory, Guide, Warning, and Temporary signs as defined in the Manual on Uniform Traffic Control Devices (MUTCD). It also features geospatial data to localize signs using their GPS coordinates. Benchmarks are presented to assess the performance of state-of-the-art deep learning based detectors.

Control and traffic signal warrant assessment of intersection sites

Frequent evaluations are required to upgrade mobility and safety at intersections. This thus paper proposes a typical scenario to identify suitable controls for installing appropriate traffic signals.Five individual intersections were studied within the Babylon province, of Iraq, and graphical methods were used to identify suitable controls. Three graphs were adopted based on recommendations from the Institute of Highway Transportation (IHT), Department of Transportation (DoT) and the Iraqi Highway Design Manual (SORB). In addition, warrants for traffic signal installation according to the Manual Uniform Traffic Control Devices (MUTCD) regulations were checked with HCS 2010 software.According to IHT recommendations, three of the five intersections should be of a priority type and the others should take on a grade separation and a roundabout or a similar signal type. According to DoT, three of five intersections should be roundabouts and the rest Ghost Islands. The SORB recommends that all intersections should be controlled or altered to interchanges. Optimisation of suitable controls for each site should thus take all three methods into account in view of restrictions on area and budget. According to MUTCD, all of the intersections justify the installation of traffic signals, though further evaluation complementary to the proposed scenario would be useful.

Analysis of Three Sign Management Program Case Studies

Traffic signs play a major role on the national highway system because they provide users with important information such as warnings, regulations, and directions. To ensure sign visibility at night, the Manual on Uniform Traffic Control Devices (MUTCD) requires transportation agencies to meet minimum sign retroreflectivity levels through a sign maintenance program. To better understand current trends, the researchers conducted an extensive literature search that showed that expected sign life and nighttime inspection are the most used methods, followed by blanket replacement. The literature does not typically discuss how these methods are implemented. Thus, the research team also contacted three of the four largest state-maintained highway systems in the United States (North Carolina, Virginia, and South Carolina) to discuss sign maintenance programs, implementation issues, and best practices. The authors describe in this article the findings and conclusions drawn from these case studies that may help other agencies improve their sign maintenance practices.

Developing and Implementing Manual on Uniform Traffic Control Devices Criteria for Selecting Traffic Control for Unsignalized Intersections

The 2009 United States Manual on Uniform Traffic Control Devices (MUTCD) 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 the current 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. This 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.

Safety Service Patrol Uniforms: Technology, National Practices, and Operator Preferences

Safety service patrols operate in more than 40 states and territories in the United States and each program operates with unique vehicles, uniforms, and equipment. Despite the variety of operator uniforms, legal and technical requirements at a national level dictate some choices, though color and style are largely at the discretion of states. Past research confirms that high-visibility safety apparel (HVSA) increases visibility. Biomotion markers on the joints further enhance visibility. The Manual on Uniform Traffic Control Devices specifies that personnel working in the right-of-way wear a Class 2 or 3 HVSA. A survey of states where service patrols operate found the majority use high-visibility yellow-green over red-orange, and Class 3 garments are preferred over Class 2. In relation to the base uniform, there is a mixture of maintenance-type uniforms, polo shirts, and no uniform specification at all. In a survey of Florida service patrol program managers and operators, conveying professionalism, comfort, and safety were the most valued aspects of uniforms. Operators understand the need to care and maintain HVSA, but may overestimate their ability to be seen at night by between two and four times the actual distance they are visible. When given a choice, operators preferred dark trousers with biomotion markers, though they were roughly split between the polo shirt/vest option and the integrated HVSA shirt that does not require use of a vest. A uniform protective outerwear was favored by almost all operators, and a ball cap was the headwear of choice.

Queue-Based Guidance for Signalization Consideration at Two and Three-Legged Intersections

This research collected and analyzed gap acceptance in North Carolina to develop a data-driven method for determining the need for considering additional signalization analysis at intersections with fewer than four legs. This method can be used for movements that merge with or cross two lanes of oncoming traffic. It is intended to provide guidance and support to traffic engineers in their decision-making process. Charts are provided to determine the expected 95th percentile queue lengths for left-turn, right-turn, and U-turn movements crossing or merging with two lanes of conflicting traffic. This situation is typically present along four-lane roadways where a one-way primary movement opposes either a minor road right-turn movement or a left-turn movement, or in the case of a median U-turn opening. Adjustment factors to the conflicting flowrate were developed to account for the presence of upstream signalized intersections. This method less frequently recommends further signal consideration when compared with the Manual on Uniform Traffic Control Devices peak hour warrant, but is similar to the delay-based level of service D/E threshold for two-way stop-controlled intersections in HCM6 Chapter 19.

Integrating Communication with Conspicuity to Enhance Vulnerable Road User Safety: ArroWhere Case Study

This paper presents findings from a research study into the role that communication plays in the safety of vulnerable road users (VRUs), including a literature review, a hypothesis, and a case study testing our hypothesis. Many governments and road authorities lack capital or have not made it a priority to implement full VRU safety measures, with many gaps in VRU infrastructure and networks. These gaps leave VRUs to take safety into their own hands, including use of conspicuity aids such as high-visibility wear, helmets, bells, and lights with differing levels of effectiveness. The knowledge gap regarding the conventional wisdom, “be safe, be seen,” is the absence of communication and comprehension between road users (VRUs and vehicles). We hypothesize that communication aids are equally, if not more important than visibility aids for VRU safety. A case study was conducted to measure the effectiveness of several Hi-Viz safety vest designs including online surveys and separate in-field experiments using Instrumented Probe Bicycles. The results suggest that Hi-Viz safety vests using arrow designs (ArroWhere’s proprietary products and designs) similar to those found in the Manual on Uniform Traffic Control Devices (MUTCD) can increase VRU safety until road authorities can fully fund and complete proper and sustainable VRU networks.

Studying the Nighttime Visibility Performance of Retroreflective Pavement Markers

Retroreflective pavement markers (RPMs) supplement or substitute for pavement markings and provide superior visibility during wet nights when the visibility of most pavement markings is significantly reduced. Many state and local agencies in the United States install and maintain RPMs even though they are not required to use them by the Manual on Uniform Traffic Control Devices. A lack of visual performance criterion for in-service RPMs results in non-uniform installation and maintenance of RPMs from agency to agency. There is a need to better establish guidance on the visual performance of RPMs. This paper develops a visibility level (VL) model to assess the visibility of RPMs, based on drivers’ visual demands. After validating the VL model for RPMs, the impacts of retroreflectivity, spacing, number of RPMs, glare, and driving speed on the visibility of RPMs are explored using the VL model. The study results not only confirm the superior visual performance of RPMs over pavement markings but also suggest the RPM performance criteria including placement criteria and minimum luminance/retroreflectivity levels.

Traffic Control Devices for Deterring Wrong-Way Movements at Unsignalized Intersections on Divided Highways

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, the research team 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.