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Publications (90)
Due to limited budget, most transportation agencies restripe their thermoplastic pavement markings based on a fixed schedule or based on visual inspection instead of monitoring the retroreflectivity and restriping when the retroreflectivity drops below a pre-determined threshold. These strategies are questionable in terms of efficiency and economy....
1 Waterborne paint is the most common marking material used throughout the United 2 States. Due to budget constraints, most transportation agencies repaint their markings 3 based on a fixed schedule, which is questionable in terms of efficiency and economy. To 4 overcome this problem, state agencies could evaluate the marking performance by 5 utili...
In Louisiana, most districts restripe their roadways using waterborne paints every other year; this strategy is questionable in relation to efficiency and economy. Previous studies show substantial variability in paint service life throughout the U.S.A., ranging between 0.25 and 6.2 years. Shortcomings in modeling the retroreflectivity of waterborn...
While there has been increasing interest in wet-weather pavement markings due to their improved visibility and potential for enhancing road safety in wet-night conditions, there is a lack of research evaluating their safety effectiveness based on actual wet-night crash data. This paper presents the safety assessment of wet-weather pavement markings...
Because the important task of traffic signs is to provide drivers with valuable information, the replacement of ineffective signs leads to a safer and more efficient environment for road users. Previously, many researchers studied traffic signs from the perspective of the road user. However, research regarding the identification of factors contribu...
Upgrading traffic signs can benefit all drivers, especially older drivers. A key to recognizing and quickly comprehending signs is to under-stand the meaning of the various shapes and colors. Both daytime and nighttime drivers need conspicuous, legible signs in order to make important decisions at key locations, such as high-speed roadways, interse...
Overhead guide sign lighting has been used by many agencies to improve visibility. However, the availability of newer and more efficient retroreflective materials has created a new challenge for state transportation agencies going through sign sheeting upgrade programs and considering the need for using sign lighting, as there is no existing answer...
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...
Guidelines for the provision of effective nighttime performance of overhead signs were developed. Relevant policies and guidelines with regard to sign lighting currently provide little useful information to determine when sign lighting is needed, and the reference material available to practitioners is out of date. Two complementary nighttime visib...
The City of Albuquerque, New Mexico has upgraded its traffic signs in several sections of the city. The upgrade process replaces all traffic signs with signs made from new materials. Because sign improvements are traditionally made on a case-by-case basis, as funding challenges can limit an agency's ability to implement widespread changes, this sig...
This research project focused on determining effective messages for encouraging drivers to leave their vehicles and evacuate a tunnel on foot, determining sign and marking formats that most effectively lead people to emergency tunnel exits, and determining the most visible sign and marking materials and technologies for use in highway tunnel enviro...
Warning signs are used to warn road users of potential hazards located in or near a roadway. A properly placed warning sign provides the road user with adequate time to select and execute the proper response. Table 2C-4 in the 2009 edition of the Manual on Uniform Traffic Control Devices presents recommended advance placement distances for warning...
Researchers evaluated the effectiveness of traffic control device (TCD) treatments for changes in horizontal alignment through two studies. The first study evaluated the behavior of 103 unfamiliar drivers who navigated through 167 individual changes in alignment on two-lane highways at three test sites in three states. Driver behavior instrumentati...
The objective of this study was to investigate the concern that signs along rural highways can be so bright that they cause reduced legibility or glare, or both, to the point of their being a safety hazard. The researchers recruited participants and conducted visibility studies on a closed-course facility to assess how various levels of brightness...
For more than a decade, the proportion of American Indians and Alaskan Natives killed in motor vehicle related crashes (per population of 100,000) has been much higher than that of other ethnic groups in the United States. Between 1975 and 2002, the number of fatal motor vehicle crashes increased by 52.5% on Indian reservations, while the number de...
The retroreflectivity of longitudinal pavement markings is expected to improve safety on rural highways. However, the few available research reports focused on the relationship between retroreflectivity and safety have found mixed results. New insights into such a relationship by using generalized linear mixed-effects models are provided. With this...
This paper presents an innovative method of visualizing eye-tracking data by using heat maps (color-coded contour maps showing distributed data). Heat maps of eye fixation points were created from data collected while drivers navigated a rural road. Comparable road segments were used to identify how a driver's visual attention changed while the dri...
As one external lighting source on the road, headlamps from adjacent vehicles in the stream traffic should not be ignored. No comprehensive study has yet been developed for exploring the influence of sign luminance produced by other vehicle headlamps. In this paper, a luminance calculation model is developed to calculate sign luminance from all pot...
This research was initiated to determine whether a correlation between pavement marking retroreflectivity and safety could be established. Previous research on this topic provided mixed results and sometimes counterintuitive findings. Using data from Michigan, the researchers evaluated relationships between crashes and longitudinal pavement marking...
Traditionally, retroreflectivity is used to quantify the visibility of traffic control devices, including pavement markings. However, retroreflectivity is a physical property of a material that is used as a surrogate for luminance. By itself, retroreflectivity is limited to describing the visibility of pavement markings at night. One way to quantif...
Researchers have developed a systematic method of using image-processing techniques to assess the complexity of the background of overhead guide and street name signs under nighttime driving conditions. These techniques are used to extract image properties such as entropy, contrast, energy, homogeneity, the number of saturation pixels, the edge rat...
Driving is often considered a visually oriented task. This visual task is constrained when drivers drive at night. Visibility is reduced because visual cues available during the day are not present at night. This study attempted to develop a link between driver safety and the nighttime visual environment. This research required creating and integra...
Pavement markings contribute to motorist safety by providing much-needed guidance along the roadway in both daytime and nighttime conditions. Basic characteristics of pavement marking, such as color, width, and placement, are defined clearly in the current Manual on Uniform Traffic Control Devices; however, nighttime visibility is not. Roadway agen...
The objectives of this research were to evaluate the influence of stepping distance on average, dry retroreflectivity measurements of profiled and rumble stripe pavement markings through the use of a portable (handheld) retroreflectometer and to compare these measurements with ones made with a mobile retroreflectometer. The retroreflectivity of fla...
Roadway traffic signs are a fundamental medium for conveying critical information to the road user. In 2009, the Manual on Uniform Traffic Control Devices (MUTCD) set minimum retroreflectivity requirements for such signs. Developing sign management strategies on the basis of service life is one approach to achieving compliance with minimum MUTCD si...
Historically, pavement marking materials (PMMs) have been prequalified or selected mainly on the basis of product specifications and lab testing, which do not always correlate well with the field performance of the products. Although different configurations of field test decks exist for assessing the performance of markings, no consensus exists on...
One of the most important aspects of a safe and efficient roadway is the uniform application of pavement markings to delineate the roadway path and specific traffic travel lanes. Pavement markings can communicate information to road users as no other traffic control device can. They provide continuous information to road users related to roadway al...
This paper presents the findings of a dynamic pavement marking visibility study conducted as part of the FHWA Highways for LIFE Technology Partnerships Program Temporary Wet-Weather Pavement Markings for Work Zones project. Three prototype optics-on-paint marking systems employing high refractive index dual-optics drop-on elements were evaluated at...
Research was conducted to review and develop minimum levels for pavement marking retroreflectivity to meet nighttime driving needs. A previous study performed in the 1990s using a computer model called the Computer-Aided Road-Marking Visibility Evaluator resulted in a table of minimum levels of pavement marking retroreflectivity values that FHWA us...
Research was conducted to evaluate drivers' understanding of red retroreflective raised pavement markers (RRPMs) on two-lane and four-lane undivided and divided roadways. The study included 191 participants, equally divided between three participant groups: drivers from countries with left-hand drive (e.g., Australia, United Kingdom, and Japan), dr...
Revision 2 of the 2003 edition of the Manual on Uniform Traffic Control Devices (MUTCD), which became effective in January 2008, adds new provisions regarding sign retroreflectivity. The new MUTCD language lists various assessment and management methods recommended to manage sign retroreflectivity.
Wet weather performance of pavement markings has received increased emphasis with the availability of new products designed specifically to improve nighttime visibility in wet weather conditions. Procedures for measuring the performance of these and standard marking materials are found in ASTM E1710, E2176, and E2177, which describe retroreflectivi...
The objective of this research was to determine whether the presence of transverse rumble strips is an effective warning device for drivers approaching rural stop-controlled intersections. Rural highways are associated with long tangents and infrequent intersections, which can cause drivers to become inattentive. To evaluate the effectiveness of tr...
Research findings have shown that centerline rumble strips (CRSs) and shoulder rumble strips (SRSs) have significant safety benefits. SRSs have proved successful in reducing run-off-the-road crashes, and more recent research has shown that CRSs can potentially reduce head-on collisions. However, concerns about the operational effects of CRSs and SR...
An important consideration for any traffic control device is drivers' responses to the installation of that device. One way to measure driver response or driver behavior is to study erratic maneuvers. Erratic maneuvers demonstrate confusion or surprise experienced by the driver and can possibly compromise road safety. It is especially important to...
Daytime high-speed passing maneuvers were recorded along a straight and flat 15-mi section of a rural two-lane, two-way highway in Texas. The posted speed limit was 70 mph. Passing maneuvers were covertly recorded from the overtaken vehicle, which was driven at three specific study speeds: 55, 60, and 65 mph. A total of 105 single-vehicle daytime p...
Research findings have shown that centerline rumble strips (CRSs) and shoulder rumble strips (SRSs) have significant safety benefits. SRSs have proved successful in reducing run-off-the-road crashes, and more recent research has shown that CRSs can potentially reduce head-on collisions. However, concerns about the operational effects of CRSs and SR...
An important consideration for any traffic control device is drivers’ responses to the installation of that device. One way to measure driver response or driver behavior is to study erratic maneuvers. Erratic maneuvers demonstrate confusion or surprise experienced by the driver and can possibly compromise road safety. It is especially important to...
The objective of this research was to determine whether the presence of transverse rumble strips is an effective warning device for drivers approaching rural stop-controlled intersections. Rural highways are associated with long tangents and infrequent intersections, which can cause drivers to become inattentive. To evaluate the effectiveness of tr...
Daytime high-speed passing maneuvers were recorded along a straight and flat 15-mi section of a rural two-lane, two-way highway in Texas. The posted speed limit was 70 mph. Passing maneuvers were covertly recorded from the overtaken vehicle, which was driven at three specific study speeds: 55, 60, and 65 mph. A total of 105 single-vehicle daytime p...
The transportation profession is seeking to better understand the features that influence roadway speeds. Engineers need an appreciation of which roadway design features, or the values for the features, clearly relate to the speed performance on a facility. This Study utilized free-flow speed data collected at 79 tangent sites in Suburban/urban and...
Techniques to obtain horizontal curve radii were identified and tested in a controlled experimental study. Ten techniques were identified and pilot tested. Eight of those initial 10 were then used to measure 18 hori- zontal curves on two-lane rural highways in Texas to evaluate fully their accuracy, precision, cost, ease of use, and safety. Statist...
The human factors study being reported measured drivers' estimates of horizontal curvature as a function of the size and spacing characteristics of post-mounted delineators. The study also assessed drivers' understanding of delineator color applications. The main objective of this study was to provide support for simplifying delineator applications...
The chevron alignment sign is an important traffic control device used to warn drivers of the severity of a curve by delineating the alignment of the road around that curve. FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways provides the following guidance on the spacing of chevrons around a curve: "The Chevron Alignment sign...
A supply vs. demand luminance concept is currently employed to provide a metric to set minimum retroreflectivity levels. Supply luminance depends on reliable modeled estimates of luminance directed back toward the driver. A small pocket of literature shows inconsistent relationships between measured and modeled illuminance and luminance levels. One...
The legibility of full-scale guide signs was evaluated in a controlled field study. The objective was to determine how the legibility of unlit guide signs could be maximized with combinations of font and retroreflective sheeting. Two fonts were tested: Series E (Modified) and Clearview 5WR, a modified version of Clearview 5W. Five combinations of r...
The legibility of full-scale guide signs was evaluated in a controlled field study. The objective was to determine how the legibility of unlit guide signs could be maximized with combinations of font and retroreflective sheeting. Two fonts were tested: Series E (Modified) and Clearview 5WR, a modified version of Clearview 5W. Five combinations of r...
The human factors study being reported measured drivers’ estimates of horizontal curvature as a function of the size and spacing characteristics of post-mounted delineators. The study also assessed drivers’ understanding of delineator color applications. The main objective of this study was to provide support for simplifying delineator applications...
The chevron alignment sign is an important traffic control device used to warn drivers of the severity of a curve by delineating the alignment of the road around that curve. FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways provides the following guidance on the spacing of chevrons around a curve: “The Chevron Alignment sign...
Techniques to obtain horizontal curve radii were identified and tested in a controlled experimental study. Ten techniques were identified and pilot tested. Eight of those initial 10 were then used to measure 18 horizontal curves on two-lane rural highways in Texas to evaluate fully their accuracy, precision, cost, ease of use, and safety. Statistic...
A supply vs. demand luminance concept is currently employed to provide a metric to set minimum retroreflectivity levels. Supply luminance depends on reliable modeled estimates of luminance directed back toward the driver. A small pocket of literature shows inconsistent relationships between measured and modeled illuminance and luminance levels. One...
Recent research in the United States has focused on the development of minimum retroreflectivity levels for traffic signs. The engineered approach uses a supply luminance versus demand luminance concept to achieve a metric that can be used to set minimum retroreflectivity levels. The supply luminance depends on reliable modeled estimates of headlam...
Researchers examined the impacts of various sign conspicuity enhancements on traffic operations and driver behavior in Texas. Eight types of applications were evaluated: fluorescent yellow chevrons, fluorescent yellow chevron posts, fluorescent yellow curve signs, fluorescent yellow ramp advisory speed signs, fluorescent yellow stop ahead signs, fl...
Prepared for Transportation Research Board, Washington, D.C. 82nd Annual Meeting, January 2003 Paper #03-2642, Words: 4744 + 5*250 (tables) + 5*250 (figures) = 7244 TRB 2003 Annual Meeting CD-ROM Paper revised from original submittal.
Background and current status of the development of updated minimum in-service retroreflectivity levels for traffic signs in the United States are described. A summary of the earlier work, conducted from the late 1980s to the mid-1990s, is provided along with descriptions of the relevant validation work. Related events that occurred in the late 199...
A study was conducted to determine the legibility impacts of freeway guide signs when encapsulated retroreflective sheeting is replaced with microprismatic retroreflective sheeting. The study included freeway guide signs mounted in an overhead position and exclusively illuminated with vehicle headlamps. A total of 60 subjects divided into three age...
The legibility of the Clearview alphabet on freeway guide signs constructed with microprismatic retroreflective sheeting was studied. The Clearview legibility results were compared to the legibility of freeway guide signs constructed with the Series E (Modified) alphabet. A total of 60 subjects divided into three age groups participated in this nig...
Research and recommendations were produced on the basis of a study on the development of minimum retroreflectivity values for overhead guide signs And street name signs. The research reviewed the literature and available photometric models. A photometric model was created to develop minimum retroreflectivity values for overhead guide signs and stre...
A revised definition for design speed has been adopted by AASHTO and included in the 2001 Green Book. Although this revised definition addresses several concerns, it does not include guidance on how to select the most appropriate design speed value. A summary of AASHTO policy, state practices, and international practices with regard to design speed...
Photometric models can be used to estimate the sign luminance provided for different roadway scenarios. While photometric models provide specific luminance curves, no standards or design criteria exist that can be used to define how much luminance is needed by a driver. For instance, if one desired to design a sign based on an assumed design driver...
Rural roads with an average daily traffic (ADT) of less than 2000 vehicles per day represent more than half of all lane-miles of highway maintained by the Texas Department of Transportation (TxDOT). As the state's highway system continues to age, maintenance activities on these facilities are becoming increasingly common. The Texas Manual on Unifor...
An evaluation of the effectiveness of speed displays and portable rumble strips at reducing speeds in rural-maintenance work zones is described. Speed displays are radar-activated signs that dynamically display approaching vehicle speeds. The devices were tested on two-lane low-volume, high-speed rural roads where maintenance activities were comple...
In 1993, the Federal Highway Administration (FHWA) published research recommendations for minimum levels of retroreflectivity for traffic signs. These values were later revised in a 1998 FHWA report. The minimum values were developed as part of a process to add end-of-service life retroreflectivity values to the "Manual on Uniform Traffic Control D...
Many roadway factors have an effect on driver behavior. Geometric, roadside, and traffic control device variables that may affect driver behavior on four-lane suburban arterials were investigated. Traffic signals and traffic volume were considered within the study site selection and data collection criteria and, therefore, were not included in the...
This report documents the first year activities of a two-year project in which various work zone traffic control devices, treatments, and practices were implemented and evaluated. The focus has been on rural high-speed work zones. Nine work zones have been studied. Four work zones have been on two-lane highways with flagger operations and the remai...
This report documents the second year of a two-year project to evaluate the effectiveness of innovative work zone traffic control devices. Researchers evaluated these devices at short-term rural work zones. During the second year of the project, seven devices were tested at eight work zones. The devices evaluated included portable rumble strips, po...
Results of research conducted to investigate the short-term effects of the double-fine law in work zones implemented in Texas on January 1, 1998, are presented. Field studies of traffic speeds in several work zones were performed before and after the law was implemented. Traffic citation data for these same work zones were also obtained from the Te...
The objective of the current AASHTO criteria for horizontal curve design is to select the radius and superelevation so that the lateral acceleration perceived by the occupants of vehicles traversing horizontal curves is kept within comfortable limits. It is considered good design practice to provide roadways on which these comfortable lateral accel...
In 1995, legislation was passed by the 74th State Legislature of Texas requiring the Texas Department of Transportation to install and operate automated enforcement systems at up to 10 highway-railroad grade crossings as a demonstration project. An issue that arose early was determination of which gated crossings were best suited for automated enfo...
NCHRP Project 15-18 evaluated how speed is used within existing practices and developed recommended changes. The strongest statistical relationship between operating speed and roadway characteristics on suburban tangent sections was with posted speed limit. Other variables that showed potential influence on 85 th percentile free-flow operating spee...
In a recently completed study, researchers evaluated the performance of various pavement markings during wet and dry nighttime conditions to obtain a better understanding of how a wide range of markings perform, and how their performance can be assessed. The results of the full study are published elsewhere (1,2). The key focus of this paper is to...
TRB’s Transit Cooperative Research Program (TCRP) and National Cooperative Highway Research Program have jointly produced and published Improving Pedestrian Safety at Unsignalized Crossings. The product, which can be referred to as TCRP Report 112 or NCHRP Report 562, examines selected engineering treatments to improve safety for pedestrians crossi...
