Manual On 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.

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.

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.

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.

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.

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.

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.

Current Attitudes among Transportation Professionals with Respect to the Setting of Posted Speed Limits

A recent survey conducted by the National Committee on Uniform Traffic Control Devices Task Force explored current and potential approaches to the setting of posted speed limits. The survey was distributed in the spring of 2018 and gathered 740 responses. The survey found that many states and local agencies have their own laws or criteria for the setting of speed limits (many are very detailed). Professionals who perform posted speed limit studies rarely only use the 85th percentile speed. It is clear from the survey that analysts who establish speed zones utilize many factors beyond the 85th percentile in their studies, including the context, that is, where the street is and what function it serves. The use of the 85th percentile for rural roads or interstate/freeways is different from urban streets (on urban streets, the 85th percentile plays a less significant role). The industry knowledge and use of USLIMITS2 are very limited. USLIMITS2 is a web-based tool designed to help practitioners set speed limits and is maintained by the Federal Highway Administration. Setting of reasonable speed zones requires consideration of many factors that are currently not well defined in the Manual on Uniform Traffic Control Devices (MUTCD). These factors are best defined as part of national guidance/research or local policy documents and do not need to be defined in the MUTCD as they can involve state/local interpretation.

An analysis of highway work zone safety practices in Pakistan

Highway Work Zones (HWZs) present a major hazard for road users, construction workers and equipment, and significantly contribute to occurrence of road crashes worldwide. The present study focuses on analysing the current state of safety measures at HWZs in Pakistan. A more direct approach is adopted by comparing safety measures at randomly selected HWZs in Pakistan with well-established safety procedures in Manual on Uniform Traffic Control Devices (MUTCD). HWZ safety measures such as traffic signs, markings, safety measures for pedestrians, workers and construction machinery, police enforcement, speed control measures, provision of advance warning area, buffer spaces, transition areas, and tapers for eight different HWZs were studied and compared with MUTCD standards. The results revealed that majority of the HWZs in Pakistan do not conform to any standard layout especially for safety and speed control measures. An enhanced need for special efforts towards improving safety at HWZs in Pakistan is highlighted.

Truck safety evaluation on Wyoming mountain passes

The Manual on Uniform Traffic Control Devices (MUTCD) for Streets and Highways recommends hill signs be placed in advance of downgrade descent of mountain passes. Mountain passes increase the risk of a runaway, or out of control trucks and so the advance warning signs inform the driver to take special precautions such as reducing speed or using lower gears during the descent. The Wyoming Department of Transportation has installed steep grade advance warning systems on Wyoming mountain passes. However, concerns for out of control trucks on the mountain passes persist. The objective of this study is to evaluate the safety effectiveness of steep grade advance warning signs for trucks on Wyoming mountain passes. The safety evaluation was carried out by implementing a zero-inflated negative binomial modeling technique for predicting truck crashes on mountain passes. The outcome was two models that showed the risk of runaway truck accidents were high at locations where either the grades were steep and long or the grades were long with multiple vertical curves. The analysis showed the current advance warning systems were not significantly impacting truck crash risks at the high risk locations. The study, therefore, recommends some improvements to the current advanced warning signs or implementing an improved Federal Highway Administration Grade Severity Rating System based warning system that will significantly improve truck safety at the hazardous locations. The study informs policy makers on the safety issues on Wyoming Mountain passes with regards to runaway trucks and makes recommendations for reducing the risk of runaway truck crashes on mountain passes.

Traffic control devices for deterring wrong-way driving: Historical evolution and current practice

Abstract Each year, hundreds of fatal wrong-way driving (WWD) crashes occur across the United States. Thousands of injuries are reported in crashes caused by wrong-way drivers. Traffic control devices (TCDs), i.e., signs, pavement markings, and signals, have been introduced since 1935 to combat this problem. The aim of the paper is to provide a complete history of TCDs for deterring WWD on freeways and divided highways in previous versions of the Manual on Uniform Traffic Control Devices (MUTCD) (1935–2009). A fully referenced overview of definitions, text passages, and figures of the TCDs, employed to deter WWD in all MUTCD versions, will be given to characterize the changes over time. In addition, the efforts that have been made by state department of transportation (DOT) especially over the past few years to aggressively attack WWD by deploying standard TCDs are reviewed. Finally, the paper makes conclusions and recommendations with regard to the necessity of a revision in the next edition of MUTCD for WWD TCDs. The investigation of changes and the current practice leave a trail to enable traffic engineers and policy makers to consider past decisions and their effectiveness in combating WWD, as well as providing a reference to determine whether or not their jurisdiction meets the MUTCD standards.

Field Evaluation of Pilot Vehicles and Portable Traffic Control Signals With and Without a Flagger

The national Manual on Uniform Traffic Control Devices (MUTCD) does not prohibit the use of a pilot vehicle in conjunction with portable traffic control signals (PTCSs), but it does require that a flagger be stationed on the approach to the activity area where a pilot vehicle is being used. This negates the main advantage of using PTCSs—the removal of the flagger from the transition area. To assess compliance with pilot vehicles and PTCSs with and without flaggers, field studies were conducted at lane closures on two-lane, two-way roads in Texas. Only 2.7% and 2.3% of drivers did not comply with the PTCSs and pilot vehicle for both conditions studied (with and without a flagger, respectively). The similar violation rates between treatments showed that there was no significant or practical difference between violations at a PTCS with and without a flagger when a pilot vehicle was used. The overall recommendation is that the national MUTCD be changed to allow the use of a pilot vehicle in conjunction with PTCSs without a flagger at lane closures on two-lane, two-way roadways. In an effort to provide pilot vehicle drivers, especially those with less experience, an initial estimate of the minimum green time needed to clear the vehicle queue at the PTCS, an easy tool was developed.

Effects of Full Matrix Color Changeable Message Signs on Legibility and Roadway Hazard Visibility

Transportation agencies are considering public–private partnerships as they struggle to fund infrastructure and operations improvements. The national Manual on Uniform Traffic Control Devices (MUTCD) allows acknowledgments of private sponsors on static signs. The legibility and visibility impacts of including logos of sponsors on changeable message signs (CMSs) were examined. Thirty drivers participated in a closed-course study during daytime and nighttime conditions. Full-sized full matrix color LED signs were used to display travel time and safety reminder messages with and without sponsor acknowledgment logos. Single- and dual-phase messages were tested. The measures of effectiveness were legibility distance for target words on the signs and roadway hazard object detection distance. Legibility distances of the CMS messages were notably greater than those of retroreflective traffic signs and well above the MUTCD threshold of 30 ft/in. During the day, the median legibility index was approximately 60 ft/in. At night, the index was approximately 45 ft/in. Sponsor logos had no significant effect on the legibility distances of travel time signs. Sponsor logos had a small effect on the legibility distance of safety message signs with a blue background but not on those with a black background. The use of sponsor logos marginally affected object detection for certain object locations. The results of this study, coupled with an earlier driving simulation evaluation showing no cognitive distraction due to logos, support the use of sponsorship acknowledgment signs on CMSs. An open road evaluation is planned before statewide implementation is enabled.

Effectiveness of Using Diagonal Yellow Arrows on Lane-Use Control Signals

Lane-use control signals (LUCSs) are important elements of a traffic management strategy for mitigating congestion and enhancing safety, especially during peak travel times. The Manual on Uniform Traffic Control Devices (MUTCD) allows the use of a downward green arrow indication as well as a yellow X-indication and a red X-indication. In 2014, the Virginia Department of Transportation requested and obtained FHWA approval for an experiment to evaluate the diagonal downward yellow arrow indication. Previous studies had shown that this indication had several benefits relative to the yellow X-indication. A stated preference survey was conducted to evaluate driver understanding of LUCSs on I-66 and on I-95 express lanes. Survey results indicated that more than six times as many participants preferred the diagonal downward yellow arrow indication to the yellow X-indication, regardless of driver age or travel frequency on the test corridors. Traffic operations center staff anecdotally observed several positive changes in driver behavior while the diagonal downward yellow arrow indication was in use. Preliminary operational and safety results were reviewed after deployment of the diagonal downward yellow arrow indication. Results indicated that driver understanding of the diagonal downward yellow arrow indication was superior to that of the MUTCD-approved yellow X-indication, and no negative effects on safety or operations were observed. The diagonal downward yellow arrow indication appears to be a useful new LUCS indication and could improve traffic management.

Investigation of Alternative Bicycle Pavement Markings with the Use of a Bicycle Simulator

The past decade has seen increased public interest in sustainable transportation modes in the United States. However, there is a relative lack of guidance regarding standards and specifications for bicycle facilities compared with the highway mode. This project sought to address this deficiency through the investigation of alternative pavement markings for bicycle wayfinding and proper bicycle placement at signalized intersections as part of the federal Nonmotorized Transportation Pilot Program in Columbia, Missouri. This evaluation was accomplished with a bicycle simulator study and postsimulator survey with 27 participants. A network of 37 intersections with characteristics similar to intersections in Columbia was created with the ZouSim simulator. The survey included questions regarding bicycling habits and preferences for the alternative markings. For wayfinding, two alternative types of pavement markings and the signage recommended by the Manual on Uniform Traffic Control Devices (MUTCD) were evaluated. Both the survey and the simulator results indicated that the Type 2 wayfinding markings with a green circle performed better with respect to visibility and delineating the bicycle route. The bicycle placement portion of the study investigated three alternative types of markings as well as the MUTCD markings and signage to help riders position their bicycle at the correct location to receive a green signal. The bicycle placement results indicated that the Type 1 and Type 2 experimental detector markings resulted in the fewest number of missed detections, while the Type 1 marking was the preferred alternative of the survey participants.

Exploring environmentally sustainable traffic signal warrant for planning application

ABSTRACTWith the concerns over the greenhouse gas (GHG) emissions associated with the surface transportation, the environmentally sustainable traffic signal warrant is essential to provide guidelines for making environmentally conscious decisions about control types at intersections. This research conducted a pilot study on developing CO2 emissions-oriented traffic signal warrants. Intersection control types that were analyzed for this research include two-way stop, four-way stop, traffic signal, and roundabout. Two environmentally sustainable traffic signal warrants were proposed: Type I (without roundabout) and Type II (with roundabout). The proposed traffic signal warrants were compared with the existing mobility-oriented traffic signal warrant of the Manual on Uniform Traffic Control Devices (MUTCD) in terms of CO2 emissions and total delay. The measurements were collected and estimated using a microscopic traffic simulation tool, Verkehr In Stadten—SIMulationsmodell (VISSIM). The environmentally sustainable traffic signal warrants show that the annual CO2 emissions of the ground transportations in the USA were reduced by 7.2% with Type I warrant and 13.9% with Type II warrant.

The effects of damage on sign visibility: An assist in traffic sign replacement

Abstract Traffic signs often convey critical information to drivers. To ensure visibility in nighttime or low light conditions, traffic signs must be in compliance with the minimum retroreflectivity standards outlined by the manual on uniform traffic control devices (MUTCD). Among all of the assessment methods (visual nighttime inspection, retroreflectivity measurement) and management methods (expected life, blanket replacement, and control signs) outlined in the MUTCD, expected sign life has been the most selected by agencies for maintaining compliance. In current literature, little research exists with regard to schedule sign replacement, focusing rather on the current favorite predictor, sign age. However, after collecting data on 1683 in-service traffic signs across the state of Utah, this study primarily concluded that not only sign age, but other contributing factors affect sign retroreflective performance. Aiming to determine the effects of various damage forms on sign retroreflectivity, statistical methods, including regression models, chi-square test, t -test, and odds ratio were employed to analyze traffic sign data. At the conclusion, the strong association between damage and retroreflectivity compliance of traffic signs was evident. In addition, to identify more critical damage forms, the effects of various forms on traffic sign retroreflectivity were compared. These conclusions provide insight to inform transportation agencies in the development of sign management plans and schedule sign replacement.

Model Development for Use of Portable Traffic Signals in Conjunction with Pilot Car Operations at Two-Lane, Two-Way Rural Highway Work Zones

A portable traffic signal (PTS) system is a traffic control device designed to facilitate the movement of one-way traffic at work zones where there is a temporary lane closure. The 2009 edition of the Manual on Uniform Traffic Control Devices (MUTCD) provides minimal guidance for the use of PTS systems with a pilot car, flaggers, or a pilot car and flaggers. Furthermore, the MUTCD also gives minimal guidance on appropriate signal timings and the traffic volume thresholds for work zones at which a PTS system might fail, and safety could be compromised. Therefore, the objective of this study was to develop a model and provide guidelines for the use of PTS systems in conjunction with pilot car operations by using factors such as the roadway average annual daily traffic (AADT), length of the work zone, length of the green interval, and the pilot car’s round-trip time. Over a 4-week period from August 5, 2014, to August 28, 2014, 161 h of video data were collected at four rural highway work zones in Kansas. The video field data were used to calculate the values for saturation headway and start-up lost time, which were 3.3 s and 6.0 s, respectively. The developed equations and the existing Kansas Department of Transportation policy of a maximum round-trip time for the pilot car of 15 min and a maximum pilot car speed of 40 mph were used to determine that PTS systems would fail to accommodate all traffic at and above AADTs of 7,083 vehicles per day and at a corresponding maximum green time of 446 s.

An automated sign retroreflectivity condition evaluation methodology using mobile LIDAR and computer vision

Traffic sign retroreflectivity condition is one of the most critical factors impacting nighttime driving safety. The federal rule on minimum traffic sign retroreflectivity incorporated in the 2009 Manual on Uniform Traffic Control Devices (MUTCD) issued by the Federal Highway Administration (FHWA) is compelling transportation agencies to evaluate how to comply. As the traditional manual methods have become financially and/or practically infeasible, there is an urgent need for an effective and efficient retroreflectivity evaluation method. This paper investigates the possibility and proposes a methodology for automatically evaluating traffic sign retroreflectivity condition using mobile light detection and ranging (LIDAR) and computer vision. The proposed methodology uses (a) the traffic sign detection and color segmentation methods that are introduced for the first time to evaluate the retroreflectivity of different traffic sign colors separately in an automated manner; (b) the proposed theoretical-empirical LIDAR retro-intensity normalization scheme to more reliably model the radiometric responses of traffic sign captured in the mobile LIDAR data; (c) the population-based condition assessment method for the first time to statistically quantify the retroreflectivity condition of traffic signs rather than an four-point average. An experimental test was conducted on 35 Type I Engineer Grade stop signs. The result shows that the proposed methodology can produce a promising outcome with consistent retroreflectivity evaluations based on handheld retroreflectometer measurements; the proposed methodology can, also, better identify traffic signs with non-homogeneous deteriorated retroreflectivity. The reliable retroreflectivity evaluation results make the proposed methodology an appealing alternative for transportation agencies to use to comply with the FHWA’s requirement.