<?xml version="1.0" encoding="utf-8"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>TRB Publications Index</title><link>http://pubsindex.trb.org/</link><atom:link href="http://pubsindex.trb.org/common/TRIS Suite/feeds/rss.aspx?tc=NN%3AQtbe%2A" rel="self" type="application/rss+xml" /><description></description><language>en-us</language><copyright>Copyright © 2015. National Academy of Sciences. All rights reserved.</copyright><docs>http://blogs.law.harvard.edu/tech/rss</docs><managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor><webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster><image><title>TRB Publications Index</title><url>http://pubsindex.trb.org/Images/PageHeader-wTitle.png</url><link>http://pubsindex.trb.org/</link></image><item><title>Driver Response to a Slippery Curve Warning System during Winter Weather Conditions</title><link>http://pubsindex.trb.org/view/2622032</link><description><![CDATA[This study assessed the effectiveness of a slippery curve warning system (SCWS) as a speed reduction countermeasure during winter weather conditions. A field evaluation was conducted during the winter of 2024 at two horizontal curves located on a rural highway in northern Michigan. The SCWS that existed at each curve included a pair of slippery when wet warning signs and a curve warning sign. Each SCWS sign included a series of LEDs along the border that flash during potentially slippery pavement surface conditions and are activated based on current weather and road surface data collected from onsite sensors. The evaluation was conducted during consistent daytime weather conditions that included temperatures in the upper 20°F to low 30°F and wet pavement surfaces. The flashing LED sign borders were manually activated and deactivated every 30?min during data collection periods. Light detection and ranging was utilized to track the speeds of free-flowing vehicles beginning upstream of the SCWS and continuing into the curve. The results showed that the SCWS had a significant speed reduction effect for drivers approaching the curve during winter weather conditions. With the LED sign borders flashing, on entering the curve, drivers were 65% less likely to exceed the curve advisory speed and average speeds were 0.9 to 1.5?mph lower compared with when the LED borders were not flashing. In addition, the speed reduction effect of the flashing LED borders was greatest for the fastest group of drivers, who are the most vulnerable from a crash severity risk standpoint.]]></description><pubDate>Thu, 13 Nov 2025 09:06:17 GMT</pubDate><guid>http://pubsindex.trb.org/view/2622032</guid></item><item><title>Leveraging Existing Traffic Signal Assets to Obtain Quality Traffic Counts: A Guide</title><link>http://pubsindex.trb.org/view/2582398</link><description><![CDATA[The scope of this guide is to provide transportation agencies with information about extracting motorized and non-motorized traffic volume data from existing signal assets. For completeness, the guide covers both commonly used signal assets and less commonly used but promising types of signal equipment. The guide is organized as follows: Chapter 1—Introduction;  Chapter 2—Inductive Loop Detectors; Chapter 3—Video-Based Systems; Chapter 4—Microwave Radar Sensors; Chapter 5—Light Detection and Ranging (LiDAR) Sensors; Chapter 6—Infrared Sensors; Chapter 7—Magnetic Sensors; Chapter 8—Ultrasonic Sensors; Chapter 9—Other Technologies; and Chapter 10—Data Management. For each type of equipment, the guide offers information about its operation, strengths, weaknesses, count accuracy, cost, and recommended practices for improving the accuracy of traffic volume data. Each chapter provides information on how the respective technology applies to motorized and non-motorized traffic so that users focused on a specific mode can easily find the relevant details. For clarity, the strengths and weaknesses of each technology are presented for both traffic modes combined, as well as separately for motorized and non-motorized traffic where distinctions exist. Additionally, recommendations specific to non-motorized traffic are provided separately to highlight key considerations for accurate data collection. The guide also provides recommendations for obtaining, storing, transmitting, and managing count data for traffic monitoring purposes in Chapter 10.]]></description><pubDate>Wed, 30 Jul 2025 16:56:06 GMT</pubDate><guid>http://pubsindex.trb.org/view/2582398</guid></item><item><title>Feasibility and Reliability Assessment of Inexpensive Solid-State Lidar for Rutting Measurement in Asphalt Pavement</title><link>http://pubsindex.trb.org/view/2559116</link><description><![CDATA[Rutting in asphalt pavements, characterized by longitudinal surface depressions in wheel paths, poses significant safety concerns. Accurate identification and measurement of rutting are crucial for maintaining road safety, ensuring ride quality, and reducing fuel consumption. Traditional methods, such as manual assessments, are labor-intensive, time-consuming, and prone to human error. High-frequency laser systems, while precise for pavement monitoring, are expensive, require specialized training for operation, and involve substantial maintenance costs, making them less accessible and convenient for many highway agencies and municipalities, underscoring the need for more affordable and practical solutions. This article introduces an accurate, efficient, and cost-effective alternative for rut depth measurement using inexpensive, commercial solid-state lidar (SSL) technology. The study is an investigation of the feasibility and reliability of SSL technology for measuring rutting distress in asphalt pavement. Measurements obtained using SSL technology were compared with measurements obtained using a laser rut bar system, as well as manual measurements. Specifically, for a specified road test section, the SSL system achieved a coefficient of determination (R2) of 0.81, a mean absolute error of 0.07?in., and a root mean square error of 0.08?in. Additionally, comparing SSL performance with manual measurements, the error in rut depth measurement was less than 20%. A network-level survey in Columbia, Missouri, demonstrated the SSL system’s capability for extensive pavement condition monitoring at highway speeds.]]></description><pubDate>Fri, 30 May 2025 14:15:48 GMT</pubDate><guid>http://pubsindex.trb.org/view/2559116</guid></item><item><title>Parameter Adaptive Research of Automatic Train Control Algorithm Based on Sliding Mode PID</title><link>http://pubsindex.trb.org/view/2215933</link><description><![CDATA[In existing urban rail systems, most trains are operated by automatic control, which places high demands on the control effectiveness of automatic train operation (ATO). In this study, a train operation model considering the response delay is firstly constructed. Subsequently, by analyzing and comparing the existing mainstream research methods, neural network and sliding mode control techniques were selected and incorporated into the speed control of the train. Among them, the dynamic sliding mode technique, is used to optimize the PID control effect of ATO. Single neuron and back propagation (BP) neural network algorithms are applied to the selection of PID control parameters. The study selects the difference between the actual speed of the control train and the target speed as the control objective. Through continuous optimization and iteration of the control parameters, the control accuracy of the train operation was improved. Finally, this study validates and simulates different model control methods using the actual operation data of urban rail transit. The results show that the sliding mode PID control model optimized with BP neural network performs better in terms of error distribution, average error value, and control effect variance under different simulation scenarios, showing good tracking ability and robustness. The related research results are expected to be applied to the initial selection of rail vehicle control parameters, dynamic adaptive operation control, and other fields, providing practical help to rail operators and rail signaling companies.]]></description><pubDate>Fri, 21 Jul 2023 15:07:26 GMT</pubDate><guid>http://pubsindex.trb.org/view/2215933</guid></item><item><title>Departments of Transportation Efforts to Digitize Ancillary Transportation Asset Data: A Step Toward Digital Twins</title><link>http://pubsindex.trb.org/view/2173225</link><description><![CDATA[The mission of state Departments of Transportation (DOTs) has evolved, and their perception has shifted from focusing on constructing new assets to managing and maintaining existing transportation assets and optimizing asset performance. In response to this change, state DOTs began adopting a “transportation asset management” approach, an intensive data-driven decision-making process to maintain and extend the serviceability of transportation assets throughout their lifecycle. However, state DOTs continue to face challenges in conducting cross-asset system analysis and integrating data across systems throughout the asset lifecycle. Conversely, emerging technologies, namely Digital Twins, have the potential to leverage the value of asset data and transform data into valuable insights to inform decision-making. The definition of Digital Twins in the infrastructure industry is inconsistent, and the transition toward a digitized built environment—a preliminary step required for a successful implementation of Digital Twins—has not been investigated. Thus, this paper presents the burning platform for the need for Digital Twins and defines the concept. Additionally, this study investigates the current practices of state DOTs toward the digital transition of their transportation asset data and contextualizes the DOTs’ maturity in the advancement of digital processes. This paper focuses on ancillary asset systems, particularly Roadside, Electronic, and Drainage Asset systems. A web-based survey was developed and distributed to state DOTs for data collection. For each asset, the perceived timeline for digitization was investigated, and three variables related to data digitization were explored: data format, data level of detail, and data collection technique.]]></description><pubDate>Mon, 15 May 2023 18:38:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/2173225</guid></item><item><title>Self-de-icing LED Signals for Railroads and Highway Intersections</title><link>http://pubsindex.trb.org/view/2037231</link><description><![CDATA[This Innovations Deserving Exploratory Analysis (IDEA) project was aimed at developing and demonstrating a new type of self-de-icing light emitting diode (LED) signals for highway and railroad intersections as a replacement for existing LED signal lights that remain too cold to de-ice or melt snow and could cause accidents in snowy conditions.]]></description><pubDate>Wed, 12 Oct 2022 16:35:37 GMT</pubDate><guid>http://pubsindex.trb.org/view/2037231</guid></item><item><title>NCHRP Research Report 968: Does LED Roadway Lighting Affect Driver Sleep Health?</title><link>http://pubsindex.trb.org/view/1949501</link><description><![CDATA[Traditional high-intensity discharge (HID) light sources are being replaced by light emitting diode (LED) technology, but do we know the impact of these replacements? Do LEDs with high blue content influence alertness or human health? Blue light in the wavelengths common in consumer electronics, such as tablets and monitors, is known to influence the circadian system and melatonin regulation.  National Cooperative Highway Research Program (NCHRP) Research Report 968: LED Roadway Lighting—Impact on Driver Sleep Health and Alertness documented the effects of different lighting types and their corneal illuminances on measures of drivers’ sleep health and alertness. Overall, the study results show that LED roadway lighting does not not affect salivary melatonin suppression or alertness in drivers.]]></description><pubDate>Fri, 13 May 2022 10:50:10 GMT</pubDate><guid>http://pubsindex.trb.org/view/1949501</guid></item><item><title>LED Roadway Lighting: Impact on Driver Sleep Health and Alertness</title><link>http://pubsindex.trb.org/view/1846319</link><description><![CDATA[The broad goal of this project was to determine the impact of the light emitting diode (LED) roadway lighting on driver sleep health and alertness. Sleep health was evaluated based on melatonin levels in saliva. Driver alertness was measured objectively using driver detection and color recognition distances, percentage of time that a driver’s eyelids are closed over a three-minute segment (PERCLOS) and standard deviation in lane position (SDLP) as well as subjectively using the Karolinska Sleepiness Scale (KSS). Ten healthy participants between the ages of 18 and 30 years with steady sleep-wake cycle participated in the study. Each participant encountered one light type and level in each of the five experimental sessions, which were separated by a minimum of one week. At the start of each experimental session, participants were exposed to 200 lux from 11:00 PM to 1:00 AM, which is typical of indoor residential lighting. The following findings are based on the results of the study: (1) LED roadway lighting even at light levels that are higher than those specified in the Illuminating Engineering Society (IES) RP-8-18 does not significantly suppress salivary melatonin between 1:00 AM to 3:00 AM in healthy drivers; (2) There are no statistical differences in between salivary melatonin suppression between LED and high-pressure sodium (HPS) roadway lighting when measured at the same light level (roadway luminance of 1.5 cd/m² or a corneal illuminance of 1.9 lux); (3) There were no statistical differences between salivary melatonin suppression between any LED and HPS roadway lighting condition and the roadway without electrical lighting; (4) No statistically significant differences between any of the roadway lighting conditions (LED or HPS) or no roadway lighting condition were observed for objective measures of driver alertness as measured by detection and color recognition distances (reaction times), PERCLOS, and SDLP; (5) Increase in the exposure time of HPS roadway lighting resulted in a statistically significant decrease in the detection and color recognition distances. Such differences were not observed for LED or the no roadway lighting conditions; and (6) There were no statistical differences between the HPS, LED, and the no roadway lighting conditions for the subjective driver alertness as measured by KSS. Based on these findings, it can be concluded that at the light levels specified in the IES RP-8- 18, LED roadway lighting does not affect drivers’ salivary melatonin or alertness between 1:00 AM through 3:00 AM. The results from this study do not support the need to modify the guidelines for LED roadway lighting for affecting human melatonin suppression and alertness.]]></description><pubDate>Tue, 13 Apr 2021 16:42:36 GMT</pubDate><guid>http://pubsindex.trb.org/view/1846319</guid></item><item><title>Rational Basis for Light Emitting Diode Street Lighting Retrofit Luminaire Selection</title><link>http://pubsindex.trb.org/view/1760041</link><description><![CDATA[Many municipalities are beginning to undertake efforts to retrofit their existing high pressure sodium (HPS) street lighting with LED (light emitting diode) luminaires. Unlike HPS lighting systems, which are available in a limited range of standard wattages and configurations, LED street lighting systems vary widely in wattage and physical configuration. Moreover, the technological performance of LED lighting continues to improve, whereas HPS is a mature technology with substantial improvements unlikely in the future. To develop a sound basis for selecting LED lighting systems for retrofit street lighting, photometric simulation calculations under a range of pole spacing, road width and luminaire wattage were performed. The results indicated that LED luminaires can have substantially lower wattage than HPS luminaires to produce the same light levels on the road. Further, LED luminaires tend to direct more of their output onto the road compared with HPS luminaires. As a result, LED luminaires can be used that produce substantially fewer lumens overall than HPS systems. Because the white light from LED sources makes illuminated street scenes appear brighter than the yellowish light from HPS lamps, even further reductions in light output can be accomplished with LED street lighting systems to match the same visual effect under HPS.]]></description><pubDate>Tue, 16 Feb 2021 16:00:42 GMT</pubDate><guid>http://pubsindex.trb.org/view/1760041</guid></item><item><title>Evaluation of LED Roadway Lighting Upgrades on a Major Arterial</title><link>http://pubsindex.trb.org/view/1759820</link><description><![CDATA[The use of light emitting diode roadway lighting is growing throughout the U.S., because of the benefits of longer effective life and reduced energy compared to high pressure sodium (HPS) lighting systems. The technological feasibility of LED roadway lighting systems has been established, but the impacts of LEDs on the economics of roadway lighting are situationally dependent. In many municipalities, roadway lighting is owned and maintained by the local electric utility. Numerous entities suggest that substantial cost savings can be achieved if municipalities own their roadway lighting systems. Utility-owned roadway lighting is still attractive, however, for many municipalities who are not prepared to purchase and maintain their lighting network. Following a pedestrian safety study indicating that improved lighting could result in reductions in pedestrian collisions along a particular major arterial, several LED luminaire types were installed along that roadway by the local utility. The LED lighting was selected to improve the visual conditions while using less energy. Over 30% energy savings were realized, although total utility costs were reduced by less than 5%. Subjective evaluations of the previous and LED lighting revealed that the LED lighting was judged to be a substantial improvement over the HPS lighting conditions.]]></description><pubDate>Thu, 04 Feb 2021 11:00:46 GMT</pubDate><guid>http://pubsindex.trb.org/view/1759820</guid></item><item><title>Estimating Fatality and Injury Savings Because of Deployment of Advanced Wrong-Way Driving Countermeasures on a Toll Road Network</title><link>http://pubsindex.trb.org/view/1763482</link><description><![CDATA[Limited access facility wrong-way driving (WWD) crashes are typically more severe than other crashes. Deploying advanced WWD countermeasures, such as rectangular flashing beacon (RFB) and light-emitting diode (LED) technologies, at exit ramps can reduce WWD crashes, injuries, and fatalities. No previous research has developed a methodology to quantify the potential fatality and injury savings because of future countermeasure deployments. This paper developed such a methodology and applied it to Florida’s Turnpike Enterprise (FTE) toll road network. From 2011–2016, there were 53 FTE WWD crashes, resulting in 16 fatalities and annual injury costs of $37 million. The proportion of these crashes occurring during night-time was 87%. RFB and LED life-cycle injury savings and costs were determined for all 216 FTE exits. The total savings were $424 million for RFBs (benefit–cost [B/C] ratio of 23.20) and $144 million for LEDs (B/C ratio of 13.13). Deploying countermeasures at the 103 exits with the highest B/C ratios would provide 70% of the total possible savings by equipping 40% of the ramps. For the same capital investment, RFBs provide more savings than LEDs. Spending $1 million to deploy RFBs will provide similar savings as spending $3.4 million to deploy LEDs. Evaluating the existing FTE RFB and LED ramps shows that RFBs are more effective at night-time and can provide three times the savings of LEDs. The results of this paper show the improved performance of RFBs over LEDs and provide an example that other agencies could follow to identify savings and cost-effectively deploy advanced WWD countermeasures.]]></description><pubDate>Sun, 17 Jan 2021 15:33:39 GMT</pubDate><guid>http://pubsindex.trb.org/view/1763482</guid></item><item><title>Comparison of LED-Embedded Pedestrian Crossing Signs with Rectangular Rapid Flashing Beacons and Pedestrian Hybrid Beacons</title><link>http://pubsindex.trb.org/view/1739344</link><description><![CDATA[To date, the effectiveness of light emitting diode (LED)-embedded pedestrian crossing signs is not understood, despite such signs being installed and used at pedestrian crossings. A recent study by Texas Department of Transportation focused on examining driver yield rates, a surrogate safety measure, for signs installed across the state. A total of 13 sites were sampled and field observations and video footage were recorded at each site for a total of 681 staged crossings. The driver yield rate ranged from 5% to 88%, with an average of 40%, indicating that other factors affect the effectiveness of the signs. Statistical modeling results supported this finding with the main contributors to driver yield rates being vehicle volume, measured at 1 min before the staged pedestrian crossing (converted to an hourly volume for the model), operational speed (85th percentile), deviation from 12-ft lane width, and presence of sidewalk. High hourly volume, speeds 45?mph and greater, lack of sidewalks, and 12-ft lanes (no deviation from baseline 12-ft lane width) were found to affect yield probability adversely. Based on the findings from this study, LED-embedded signs would be a suitable candidate treatment at sites with sidewalks, lower operating speeds and traffic volumes, and narrow lanes. Lastly, a comparison between driver yield rates for rectangular rapid flashing beacons, pedestrian hybrid beacons, and LED-embedded signs for various posted speed limits demonstrated that, of the three treatments, LED-embedded signs have the lowest driver yield rates, especially for higher posted speed limits.]]></description><pubDate>Tue, 22 Sep 2020 14:26:50 GMT</pubDate><guid>http://pubsindex.trb.org/view/1739344</guid></item><item><title>Evaluation of Sequential Dynamic Chevron Warning Systems on Rural Two-Lane Curves</title><link>http://pubsindex.trb.org/view/1724839</link><description><![CDATA[Roadway departure crashes are a significant safety concern. The majority of these crashes occur on rural two-lane roadways, with a disproportionate number occurring on horizontal curves. The average crash rate for horizontal curves is about three times that of other highway segments. Curve-related crashes involve a number of roadway and driver causative factors, with speed being a preeminent factor. Implementing safety countermeasures on rural horizontal curves to address these crash types can improve the safety performance. Chevron alignment signs provide additional emphasis and guidance for drivers negotiating curves. To further emphasize the curve, some agencies have started using a sequential dynamic chevron warning system (SDCWS) which uses light emitting diode (LED) lights within each chevron sign to provide sequential lighted guidance through the curve. The research team evaluated 18 rural horizontal two-lane curves where a SDCWS had been implemented. Reference sites with similar characteristics were selected and included in the study. Models were developed using an empirical Bayes methodology for non-intersection (total) crashes and injury crashes. Additional countermeasures were present at some of the sites and were included in the model. Using these data, the study developed crash modification factors (CMFs) for SDCWS with a resulting CMF of 0.34 for total crashes (non-intersection) and 0.49 for injury crashes.]]></description><pubDate>Mon, 03 Aug 2020 13:33:21 GMT</pubDate><guid>http://pubsindex.trb.org/view/1724839</guid></item><item><title>Self- Deicing LED Signal for Railroads and Highway Intersections</title><link>http://pubsindex.trb.org/view/1695391</link><description><![CDATA[This project was aimed at developing and demonstrating a new type of self-deicing LED signals for highway and railroad intersections, as a replacement for the existing LED signal lights that remain too cold on the signal lens to deice or melt snow and could cause accidents in snowy conditions.  The work of this project was divided into three stages. Stage 1 work focused on laboratory development and testing of the new self-deicing LED signals.   Work in Stage 2 focused on closed-course performance and reliability tests of the fully working prototypes mounted on the roof of the research facility, and follow-up improvements on any identified issues. Work in the third and final stage involved field testing of the developed prototypes on identified highway signalized intersections and/or rail track sections. More field testing of the developed prototypes on highway intersection or railroad wayside or at-grade crossing signal lights is planned on identified test sites in six states.]]></description><pubDate>Tue, 31 Mar 2020 15:29:21 GMT</pubDate><guid>http://pubsindex.trb.org/view/1695391</guid></item><item><title>Solid-State Roadway Lighting Design Guide: Volume 2: Research Overview</title><link>http://pubsindex.trb.org/view/1681502</link><description><![CDATA[This report presents guidelines for the use of solid-state lighting (SSL) on roadways. The research for this project included a comprehensive literature review and survey of the practices of state and local transportation agencies, which was followed by a field experiment at Virginia Tech Transportation-Institute’s Virginia Smart Road. The Smart Road experiment was a series of driving tasks in the lighted test environment, where the ability of drivers to detect pedestrians and standard targets in and off the roadway was measured for SSL luminaires equipped with LED arrays of several correlated color temperatures and for high-pressure sodium (HPS) lamps used as a control.  The key outcome of this research is a proposed AASHTO guide on solid-state roadway lighting design intended to supplement the AASHTO Roadway Lighting Design Guide, 7th edition. This guide is presented as Volume 1: Guidance. Volume 2: Research Overview is the project final report, which provides experimental data and analysis supporting the contents of the guide.]]></description><pubDate>Tue, 25 Feb 2020 15:34:41 GMT</pubDate><guid>http://pubsindex.trb.org/view/1681502</guid></item></channel></rss>