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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Performance Assessment of Vehicle Headlamps</title>
      <link>https://trid.trb.org/View/840456</link>
      <description><![CDATA[A joint CIE technical committee (TC4-45) and GTB Front Lighting Working Group activity was established in August 2005 as a continuation of the GTB taskforce that had been working for two years with the objective of developing a headlamp performance rating system to be used by EuroNCAP. When EuroNCAP decided not to continue to introduce a headlamp rating system the work undertaken by GTB was transferred into the CIE structure with a view to completing the study, publishing the conclusions and establishing a technical standard. During the GTB activity a total of 48 organizations from the GTB global national delegations had contributed and 18 meetings had been held between August 2003 and April 2005. A weeklong testing event had taken place in Spain in May 2005 with the successful validation of a number of the performance parameters but further work was indicated with regard to the algorithms for the assessment of range and glare. Since its formation, the joint CIE TC4-45/GTB Technical Committee has continued to work on the refinement of the assessment of the assessment of range and glare. A second validation test event took place in Germany in March 2006 and this contributed to a revised algorithm for the calculation of passing beam and driving beam range. A test event to concentrate on the validation of the glare assessment algorithms took place in February 2007 and a further event will take place to validate the range calculations in Italy in May. This paper, presenting the status of the work of the TC4-45 overviews the assessment method being developed and provides a summary of the results of the validation testing so far completed. The full procedure and the algorithms to be used will be contained in the CIE report and consequently it is not possible to provide the detail in this paper. The objective is to complete the work and develop a CIE technical report and draft standard by the end of 2008.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
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      <title>Development of the Human Factors Guidelines (HFG) for Road Systems</title>
      <link>https://trid.trb.org/View/840594</link>
      <description><![CDATA[Although traffic safety reflects the consideration and integration of three components – the roadway, the vehicle, and the roadway user – the information needs of roadway users are often neglected in traditional reference materials used by practitioners. In response to this problem, the National Cooperative Highway Research Program (NCHRP) initiated a project to develop human factors guidelines (HFG) for road systems. The purpose of the project has been to provide the best factual information and insight on road users’ characteristics to facilitate safe roadway design and operational decisions. This paper describes the conduct and results from phase 2 of the HFG effort. Key objectives have been to review and revise HFG materials from phase 1 and to develop three new HFG chapters. The HFG currently consists of an introduction, 23 guidelines on topics such as sight distance, unsignalized intersections, signalized intersections, and construction and work zones, as well as two tutorials. A key to the success of the effort has been the involvement of a number of representative end-users, as part of both the NCHRP project panel and a separate project working group. Future efforts are needed to finish the remaining chapters planned for the HFG. When completed, the guidelines will be available in electronic format and possibly integrated with other efforts like the Highway Safety Manual and the Interactive Highway Safety Design Model. In the meantime, groups like the National Committee on Uniform Traffic Control Devices, American Association of State Highway and Transportation Officials, and Transportation Research Board committees can help in the development of the HFG by identifying candidate topics or guides needed for inclusion in the final HFG.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840594</guid>
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    <item>
      <title>Revealing Power and Road Lighting Design</title>
      <link>https://trid.trb.org/View/840616</link>
      <description><![CDATA[Since around the 1930s, lighting engineers have been trying to improve visibility and energy efficiency for road lighting. To meet the global demand for road lighting at present, however, lighting engineers are still required to improve visibility and efficiency of road lighting. In the following, applying the results on the luminance difference threshold under dynamic conditions, under which the adaptation luminance and the background luminance are not necessary the same, one of the ways to improve visibility without increasing the energy consumption for road lighting will be discussed.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840616</guid>
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      <title>Comparing Data Collection Scenarios Used for Examining Drivers' Sign Viewing Behavior: Closed Course Versus Open Road Environments</title>
      <link>https://trid.trb.org/View/840592</link>
      <description><![CDATA[This study was aimed at comparing nighttime driver sign viewing behavior on a closed course versus their sign viewing behavior on public roads. Sixteen subjects wearing eye-tracking equipment drove a route consisting of both a closed course portion and an open road portion viewing road signs. All data was collected after dark. Subjects viewed six signs, three placed on public roads and three on the closed course. The closed course signs were speed limit signs with both standard and non-standard legends and the open road signs were test signs with alphanumeric legends designed to look like speed limit signs. The three measures used to quantify driver sign viewing behavior were the number of glances to a sign, the total time a driver was looking at a given sign, and the legibility distance of the sign legend. During the entire analysis region of 900 feet, the total number of glances made to a sign did not change. When the data were broken up into the regions before and after the reported legibility distance, however, closed course signs consistently had a higher number of looks, especially before the reported legibility. Conversely, the signs on the open road were viewed for significantly longer durations during the 900-foot approach than the signs on the closed course. Finally, the legibility distances were longer for signs viewed while on the closed course.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840592</guid>
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    <item>
      <title>I-95 Corridor Mile Marker and Ramp Designation Signing</title>
      <link>https://trid.trb.org/View/840568</link>
      <description><![CDATA[Mile marker signs on interstates are both a convenience and a safety measure in that they provide travel progress information to motorists and essential location information for 911 emergency procedures. Motorists who report accidents need to be able to identify the location of a crash, so that first responders will be able to deploy help from the appropriate facility as fast as possible. Providing crash location information becomes more difficult on complex urban highway interchanges. Inadequate ramp designation signing may lead to incorrect locations being called into the 911 dispatcher. This may cause delays in providing aid. The goal of the research performed in this study was to determine mile marker and ramp designation sign effectiveness using Tarvip and a computer based sign comprehension study. Tarvip provided the letter height and the legibility distance of the mile marker and ramp signs, while the comprehension study provided the design, content, and layout of the signs.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840568</guid>
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      <title>Pavement Marking Visibility: Brighter Versus Wider</title>
      <link>https://trid.trb.org/View/840593</link>
      <description><![CDATA[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. The key focus of this paper is to present and compare the results of two different aspects from the full study. First, while it is generally accepted that pavement marking detection distances increase as the markings become brighter, an empirically derived relationship between average detection distances of pavement markings and luminance measurements of the same is presented. Second, results of detection distances using pairs of markings 4-inch and 6-inch wide are presented. The findings from these two aspects of the study are compared and used to support conclusions regarding the benefits of brighter versus wider pavement markings. Additional research is also suggested that could be used to further enhance the data presented in this paper.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840593</guid>
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      <title>Recommendations for Minimum Pavement Marking Retroreflectivity Values Based on Tarvip Analyses</title>
      <link>https://trid.trb.org/View/840590</link>
      <description><![CDATA[As traffic control devices, pavement markings relay a wide variety of information to drivers. They are unique in that drivers do not have to shift their attention away from the roadway in order to receive continuous information. Properly  implemented pavement markings convey the following information: directional information; location of the road center and edges; the presence of passing or no-passing zones, and indication that a driver is occupying the correct lane.  Pavement markings become the only means of conveying this information to the driver at night, so their proper placement and maintenance are critical for safe driving. However, in order for pavement markings to be seen by drivers at night, they must be retroreflective. Retroreflectivity is a measure of an object’s ability to reflect light back towards a light source along the same axis from which it strikes the object. In the case of retroreflective pavement markings, incoming light from vehicle headlamps is reflected back towards the headlamps, and more importantly, the driver’s eyes. This retroreflectivity in pavement marking materials is accomplished with thousands of glass or ceramic beads per square foot embedded in the marking material. Rather than scattering light, as the pavement marking material would do without the glass beads, the beads refract the incoming light in such a way that it is returned back towards the headlamps. The most common measurement of retroreflectivity in the Coefficient of Retroreflected Luminance and can be described as “ratio of the luminance of a projected surface of retroreflective material to the normal illuminance at the surface on a plane normal to the incident light”. Retroreflective measurements can be used to assess the efficiency of pavement markings in terms of their ability to retroreflect headlamp illumination. Pavement markings, like many other roadway materials, deteriorate over time. As pavement markings deteriorate, they lose their ability to retroreflect headlamp illumination. As a result, retroreflective measurements of pavement markings decrease over time. Some believe that this reduced performance is a causative agent in the rate and severity of nighttime crashes, although research has not yet quantified the relationship. While the Manual on Uniform Traffic Control Devices requires that all signs and pavement markings be illuminated or made of a reflective material, it contains no minimum in-service retroreflective requirements that these devices must meet. In 1992, Congress mandated that such standards for signs and pavement markings be developed, and research to develop these standards has been undertaken separately. The research for minimum in-service retroreflective requirements for traffic signs was accelerated, leading to a Notice of Proposed Rulemaking that was posted in the Federal Register in July of 2004. This notice also states the Federal Highway Administration’s intent to initiate minimum pavement marking retroreflectivity requirements after the final publication of the sign retroreflectivity standards. While previous research has been undertaken to recommend minimum pavement marking retroreflectivity levels, the need exists to update the earlier research in light of changes in roadway user characteristics, vehicle preferences, and headlamp performance.]]></description>
      <pubDate>Wed, 28 Nov 2007 07:41:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/840590</guid>
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    <item>
      <title>Analysis of Modeled Versus On-the-Road Field Luminance of Retroreflective Signs</title>
      <link>https://trid.trb.org/View/840434</link>
      <description><![CDATA[In an effort to obtain field luminance values provided by different sign sheeting materials, a set of white retroreflective traffic sign sheetings from various ASTM D4956 sheeting types and a newer micro full-cube microsprismatic sheeting were obtained, and white and green blank signs were constructed for each sheeting type. Blank white signs were positioned in typical right and left shoulder positions, and green signs were positioned in typical overhead mounted positions in the field. Field measurements of luminance were conducted using a CCD photometer for each mounting position for each material from inside a 2006 model year Chevrolet Trailblazer sports utility vehicle at varying distances to the signs. In general, the micro full-cube retroreflective sheeting provided the highest luminances, whereas the beaded Type III sheeting provided the lowest luminances in all sign locations. The observed luminances were below the optimal luminance levels suggested in relevant human factors literature, suggesting further room for improvement. In a parallel effort, smaller samples were cut out from the same rolls of sheeting as the signs. These samples were characterized in their retroreflective properties using a CCD-based retroreflectometer in the laboratory. These retroreflectivity data matrices were then incorporated into a computer model known as the Tarvip model, and scenarios were generated to simulate the field condition using the Tarvip model. Luminances obtained in the field are compared to the luminances calculated with the Tarvip model. In Tarvip, a median US headlamp beam pattern was used. Results show systematic differences between field luminances and model-provided luminances especially at long and short distances in absolute terms, where field luminances were generally lower than the luminances suggested by Tarvip. However, in relative ranking of materials, the model findings notably agree with the field data. The agreement in relative ranking suggests that models such as Tarvip can be used reliably in determining relative performance of sheetings, but more headlamp data are needed to determine the general distribution of actual field luminances.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/840434</guid>
    </item>
    <item>
      <title>A Review of Disability and Discomfort Glare Research and Future Direction</title>
      <link>https://trid.trb.org/View/840453</link>
      <description><![CDATA[Disability and discomfort in the nighttime driving environment have long been a topic of research. Disability glare has been fairly well defined based on the physiology of the human eye and the behavior of light as it enters the ocular media. However, discomfort glare has been less defined. Discomfort glare is not based on a physical response but rather a psychological response. Some research has shown that a person’s response to a glare source is based more on his or her emotional state than on the light source itself. Several organizations and researchers have tried to establish a requirement which must be adhered to in order to reduce the influence of glare from opposing headlamps and overhead roadway lighting on the drivers. This remains an ongoing issue with both the Commision Internationale d’Eclairage and the Illuminating Engineering Society of North America. This paper is a summary of these research attempts and a discussion of the potential of achieving this goal with future investigations.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/840453</guid>
    </item>
    <item>
      <title>Challenges to Implementation of Work Zone Lighting Guidelines</title>
      <link>https://trid.trb.org/View/840436</link>
      <description><![CDATA[Lighting is one of the most important factors for nighttime construction. Motorist and worker safety, quality of work, productivity, and worker morale are all directly related to work zone lighting. Although lighting requirements for nighttime construction have been established, there are several key impediments to the application of these requirements. In this paper, researchers identify several of the key issues that appear to constrain further improvement in work zone lighting, and discuss several high-leverage research and development opportunities available to address these issues,]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/840436</guid>
    </item>
    <item>
      <title>The Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalk</title>
      <link>https://trid.trb.org/View/840455</link>
      <description><![CDATA[Twenty-six participants evaluated a series of crosswalk lighting designs by visually detecting objects within each crosswalk location. The research was performed on a closed test track under nighttime conditions while driving a sport utility vehicle (SUV) with regular halogen headlamps. The conditions presented to each participant included varying illuminance levels (6, 10, 20, and 30 lux), varied luminaires (high pressure sodium [HPS], metal halide [MH]) and different object types (pedestrian and surrogate objects). The participant was asked to detect objects within each crosswalk location when they were confident there was an object present. The presentation of objects was varied to diminish expectation effects. The results indicated that object detection distances varied based on illuminance level, luminaire type, and object type. Object detection distance for the HPS was greatest at 30 lux and for MH at 20 lux. However, these results were moderated based on clothing color of the object. When object color was taken into consideration, pedestrians in white clothing were identified earlier under the HPS lighting condition at 20 lux. Under the MH configuration, denim-clothed objects were detected earlier compared to black-clothed objects, especially at a 20 lux lighting level. The results indicate crosswalk lighting levels provide adequate object lighting at 20 lux. Furthermore, pedestrians dressed in white clothing have superior detection distances compared to other object types.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/840455</guid>
    </item>
    <item>
      <title>Evaluation of Road-Sign Geometry Parameter Space</title>
      <link>https://trid.trb.org/View/840452</link>
      <description><![CDATA[Current retroreflective sheeting retroreflective efficiency is a function of the reflective geometry. Most sheeting specifications, such as ASTM D4956, only sample a limited number of test geometries. These geometries were chosen primarily to simplify the process in the quality control lab while having some relevance to the roadway. They were also developed when the only retroreflective sheeting used glass-bead retroreflectors, whose retroreflective performance is insensitive to changes in rotation angle (ε) or orientation angle (ω). Prismatic sheetings use a very non-rotationally symmetric optical element, the corner-cube prism and the resulting retroreflective performance can be very sensitive to small changes in geometry. Prismatic retroreflective specifications must now be more accurate in testing relevant geometries to insure that the material is providing performance on the road and not just in the laboratory. In trying to capture roadway performance, prismatic specifications can follow two approaches. One is to identify reference scenarios that occur commonly and then adding enough variation that, hopefully, other roadway scenarios are reasonably included. Another approach is to identify the limits of the geometric parameter space and then sample this area during testing. Roadway simulation software, such as the Exact Roadway Geometry (ERGO) (1) program can be used to determine the limits of roadway geometry parameters. This would allow the creation of a specification with comprehensive testing. In this paper the authors discuss the basis for the complexity of testing: namely the prismatic response to certain test angles, and how parameter space can be analyzed, and finally how the simulations compare with data collected from a real-world examination of test angles.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/840452</guid>
    </item>
    <item>
      <title>Driver Understanding of the Purpose of Red Retroreflective Raised Pavement Markings</title>
      <link>https://trid.trb.org/View/840438</link>
      <description><![CDATA[Research was conducted to evaluate drivers’ understanding of red retroreflective raised pavement markings (RRPMs) on two-lane and four-lane undivided roadways and divided roadways. The research was conducted using an innovative laptop video survey that was administered to volunteer survey participants recruited at the Honolulu International Airport. Using various pavement marking patterns, the following five roadway configurations were tested: (1) two-lane, two-way undivided roadway marked for no-passing, (2) two-lane, two-way undivided roadway marked for passing, (3) four-lane, two-way undivided roadway, (4) two-lane, one-way roadway with travel in the correct direction, and (5) two-lane, one-way roadway with travel in the wrong direction (going against the flow of traffic). For each roadway configuration, typical pavement markings were shown as a baseline condition, and then, there were three alternate marking patterns. Two of the alternative marking patterns consisted of two different combinations of supplemental RRPMs, and the third alternate pattern consisted of supplemental pavement marking arrows without RRPMs. Almost 200 survey participants completed the study, equally divided between three participant groups: drivers from left-hand drive countries, drivers from Hawaii, and drivers from the continental United States (U.S.). The general findings were: red RRPMs on one-way divided roadways used to indicate the wrong direction of travel helped drivers realize when they were going the wrong direction; red RRPMs on undivided roadways can improve driver understanding for drivers from lefthand drive countries without negatively impacting the driver understanding of drivers from Hawaii and the continental U.S.; replacing supplemental RRPMs with supplemental arrows always improved the correct response rates for all roadway configurations and for all participant groups.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/840438</guid>
    </item>
    <item>
      <title>Driver-Focused Design of Retroreflective Sheeting for Traffic Signs</title>
      <link>https://trid.trb.org/View/840437</link>
      <description><![CDATA[Typical types of retroreflective sheeting for use in most traffic signs include enclosed and encapsulated glass bead products, micro truncated cube corner prismatic products and, most recently, micro full cube corner prismatic products. These different sheeting types exhibit correspondingly different levels of sheeting performance. Historically sheeting retroreflectivity has been measured at specific photometric angle combinations, most notably 0.2 degree observation and –4 degree entrance angles. However, such measurements generally fail to correlate with on the road performance experienced by drivers in real nighttime driving scenarios. This paper discusses driver-focused design of the latest generation of retroreflective sheeting products. Of critical importance are the fractional retroreflectance or total amount of light returned to the vehicle and the distribution of that light with respect to observation angle (divergence). Fractional retroreflectance of typical retroreflective sheeting types is summarized and contrasted, as are the technologies used to increase total light return. Micro full cube corner sheeting is shown to provide the highest total light return, especially for the moderate entrance angles common in driving scenarios. Controlling the divergence of the retroreflected light (e.g. the distribution of that light with respect to observation angle) equates to controlling the appearance of signs as a function of vehicle-to-sign distance. Hence consideration of divergence during product design is critical for meeting driver needs. The importance of increased light return especially in the range of 0.5 to 1.0 degree observation angles is highlighted. Observation angles in this range correspond to the critical distances at which actual acquisition of information from signs occurs for a range of vehicle types. These critical distances are about 50 to 150 meters (164 to 492 feet). A variety of methods for controlling divergence are reviewed. Micro full cube corner sheeting is shown to provide significantly greater fractional retroreflectance and to concentrate the extra light return at critical sign distances.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/840437</guid>
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    <item>
      <title>Effect of Outdoor Lighting on Perception and Appreciation of End-Users</title>
      <link>https://trid.trb.org/View/840444</link>
      <description><![CDATA[Artificial outdoor lighting plays several important roles. In addition to functional roles such as improving visibility and providing orientation, outdoor lighting is increasingly required to contribute to the lifestyle and feeling of emotional well-being of people outside at night. In this regard, outdoor lighting can help to increase the feeling of safety and security among pedestrians, as well as to enhance the attractiveness, ambience and appearance of an illuminated area. Environmentally, it is desirable to use efficient light sources with good optical control so that the targeted area is efficiently illuminated while sky glow and unwanted stray light are minimized. At present, high-pressure sodium (HPS) lamps are widely used in outdoor applications due to their high efficacy and long, reliable lifetime. The use of these lamps however, comes at the expense of good color rendering and accurate color appearance of outdoor spaces. Recently developed ceramic metal halide lamps can solve this dilemma by providing many of the advantages of HPS along with additional key features such as more natural white light and significantly better color rendering. Related benefits of these lamps for the residents and pedestrians in the areas illuminated by them might include greater ease of facial recognition and color identification. Color provides important visual information. Color differentiation and identification can contribute to one’s ability to recognize faces or identify one’s car, for example. Moreover, in the case of reporting a criminal act, accurate color naming can provide key information about the color of the suspected person’s clothing or automobile. Indeed, an earlier laboratory study conducted by Raynham et al concluded that twice the illuminance level of HPS is required to achieve the same facial recognition distance as with white light compact fluorescent sources at typical nighttime outdoor lighting levels. The advantages of high quality white light for facial recognition is already taken advantage of in the British standard for road lighting, BS5489:2003, which allows a lower lighting level to be used in residential areas if the color rendering index of the source used is over 60. Previous investigations have suggested that people want to be able to recognize strangers from a distance of 4 m in order to feel comfortable. However it is extremely likely that this “comfort zone” distance varies significantly from one person to another and also depending on the familiarity of the environment. Improving the distance for and ease of facial recognition might contribute to increasing the feeling of safety and security of pedestrians and especially for those who feel most vulnerable. Furthermore, there are numerous papers that discuss other benefits of white light, including improved peripheral visibility at mesopic lighting levels as a result of the higher scotopic/photopic ratio compared to HPS. Peripheral (off-axis) vision is important, for example, to enable pedestrians to detect a stranger approaching from the side, before the stranger can be seen or recognized in the direct (on-axis) field of view. Off-axis vision also enables drivers who are looking straight ahead to detect persons or objects before they unexpectedly move onto the driving lane. Previous laboratory studies, supported by theoretical models, have indicated that the reaction times for detection of off-axis targets are shorter under illumination by sources with higher short wavelength emission (i.e. white vs yellow) at mesopic light levels (0.001 - ~0.3cd/m2). In this paper, the authors present results from two independent field studies of the effect of lamp spectrum on visual performance at low lighting levels found outdoors at night. These studies were performed under more realistic conditions than the previous laboratory investigations referenced above. The first study focuses on benefits for pedestrians such as facial recognition and identification of colors in their residential neighborhood. The second study addresses the detection of targets in the peripheral field of view in an actual driving test outdoor at night.]]></description>
      <pubDate>Mon, 26 Nov 2007 09:55:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/840444</guid>
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