<?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%3AQb" 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>Pilot Studies to Compare Single- and Multi-Unit Recycling Trains on Partial-Depth (Cold In-Place) Recycling Projects</title><link>http://pubsindex.trb.org/view/2686276</link><description><![CDATA[The construction of two partial-depth (cold in-place) recycling projects was monitored and the quality control results were analyzed to compare gradations produced with single- and multi-unit recycling trains, to assess the effect of recycling train forward speed on gradation, and to compare differences between emulsified and foamed asphalt recycling agents in partial-depth recycling applications. The research highlighted the challenges with variability and small sample sizes associated with in-place recycling but provided representative and consistent results between projects. The results showed that there was no discernable difference in the density and strengths of partial-depth recycling layers produced with the single- and multi-unit recycling trains. The main benefit of the multi-unit train was better control of maximum aggregate size by the on-board screens and crushing unit, however, the crushing unit did not appear to change or improve the finer portion of the gradation (i.e., material passing the 5-mm sieve), which has a known larger influence on compaction density, air-void content reduction, strength, moisture resistance, and stiffness. The recycling train type and forward speed did influence the coarse portion of the gradation (i.e., &gt;5 mm), but did not appear to influence compaction density. Test results indicated that the sections treated with emulsified asphalt had higher densities than those treated with foamed asphalt. However, there was considerable variability in materials and pavement structure along the length of the project, which probably had an influence on all results. The findings permit agencies to specify that recycling train and recycling agent choice can be the contractor’s decision.]]></description><pubDate>Thu, 02 Apr 2026 15:23:59 GMT</pubDate><guid>http://pubsindex.trb.org/view/2686276</guid></item><item><title>Identifying Key Technologies and Cluster Patterns in Intelligent Transportation Systems</title><link>http://pubsindex.trb.org/view/2483206</link><description><![CDATA[Intelligent transportation systems (ITS) have made considerable progress along with the rapid development of technologies in recent decades. Nonetheless, a comprehensive understanding of the key technologies in the ITS domain remains elusive, and current studies have yet to systematically examine correlation patterns. To address the gap, an integrated methodology combining topic modeling and co-occurrence analysis is employed. By calculating the key index integrating with the frequency, betweenness centrality, and co-occurrence intensity, the key technologies and their basic correlations are found and analyzed. Moreover, a correlation pattern identification approach is proposed, leading to the recognition of three technology cluster patterns, namely chain clusters, cycle clusters, and star clusters. According to the service packages in the Architecture Reference for Cooperative and Intelligent Transportation, the 85 ITS-related key technologies and their cluster patterns are obtained from patent data. As a result, several primary technology clusters are uncovered, such as the chain cluster for electronic toll collection, the cycle cluster containing the person, vehicle, and road elements, and the star cluster used in the traffic state measurement and warning. The proposed methodology facilitates the recognition of ITS technologies’ relevance and structure pattern and holds potential for future applications in other technological domains.]]></description><pubDate>Sat, 28 Dec 2024 16:15:59 GMT</pubDate><guid>http://pubsindex.trb.org/view/2483206</guid></item><item><title>Physics-Informed Neural Network Model for Predictive Risk Assessment and Safety Analysis</title><link>http://pubsindex.trb.org/view/2483266</link><description><![CDATA[This paper presents a physics-informed neural network (PINN) designed to predict the future locations of both vehicles and pedestrians, providing critical insights into road safety risks. By forecasting potential trajectories of road users, the proposed model informs preemptive strategies to avoid accidents. The physics model incorporates the intelligent driver model for vehicles and the social force model for pedestrians. The stochastic nature of risk evaluation is addressed by probabilistically predicting future locations based on the expected distribution in a two-dimensional open space. The framework accurately assesses the risk by predicting the future locations of vehicles and pedestrians within a 2- to 4-s time frame with approximately 2% error rates. The risk evaluation performance of the proposed framework was tested by calculating the time to collision (TTC) between vehicles and pedestrians and analyzing traffic conflicts. Leveraging the probabilistic predictions, the TTC was evaluated stochastically using Monte Carlo simulations and the Kolmogorov–Smirnov test, enabling a more granular and effective traffic conflict analysis. The developed method demonstrated over 95% accuracy when evaluating potentially dangerous events occurring within 3?s or less, providing actionable insights for improving road safety. The framework was deployed in a real-world setting, demonstrating reliable and robust test results. This comprehensive approach is expected to pave the way for more effective risk evaluation and mitigation at intersections and on roads.]]></description><pubDate>Sat, 28 Dec 2024 16:15:59 GMT</pubDate><guid>http://pubsindex.trb.org/view/2483266</guid></item><item><title>Analysis of Retrofit and Scrappage Policies for the Indian Road Transport Sector in 2030</title><link>http://pubsindex.trb.org/view/1878443</link><description><![CDATA[In India, the road transport sector contributed around 90% of total transport CO2 emissions in 2018. Air pollution from the road transport sector has detrimental effects on both air quality and human health. The policies implemented have a long-term impact on the amount of vehicle emissions and characteristics of fleet vehicles. The present study analyzes emissions from India’s road transport sector using the bottom-up activity approach model. Future vehicle stocks in India are projected up to 2030 using a hybrid growth model approach. Vehicle emissions of CO2, CO, particulate matter (PM), and NOx are analyzed for India's reference (2020) and projected years fleet (2030). The emissions from the projected fleet are subjected to different mitigation scenarios such as retrofit and scrappage policies to estimate the emission reduction potentials of these scenarios from the future fleet of India. The analysis of the study indicates that the retrofit policies are more effective in reducing vehicle emissions than the scrappage policies. Retrofit policies such as the advancement in emission norms (shift to Bharat Stage (BS)-VI from BS-IV), the increased share of compressed natural gas (CNG) vehicles, and fuel efficiency (FE) improvements have reduced vehicle emissions significantly compared to the scrappage of old vehicles from the fleet. The low impact of scrappage policies is attributed to the projected fleet’s lower share of old vehicles (10–15%). While retrofit policies have a significant impact as they largely affect 85% to 90% of young vehicles (less than ten years of age) in 2030. A combination of both policies is suggested to control future fleet emissions. The study also conducts sensitivity analysis, which indicates a significant influence of the emission factors in the vehicle emission analysis and GDP growth rates in the vehicle fleet projection.]]></description><pubDate>Mon, 20 Sep 2021 16:58:35 GMT</pubDate><guid>http://pubsindex.trb.org/view/1878443</guid></item><item><title>Incorporating Vehicle Spray of Deicing Salts in the Estimation of Corrosion Initiation Time of Highway Bridges</title><link>http://pubsindex.trb.org/view/1759007</link><description><![CDATA[Reinforced-concrete bridges located in cold regions are typically exposed to a large amount of deicing salts during winter, which causes corrosion-related deterioration of those bridges. Vehicle spray is one of the major mechanisms of transporting deicing salts from the road surface to the exterior surface of a bridge. However, it is seldom considered in current corrosion analyses. This article proposes a method to incorporate the vehicle spray mechanism in the estimation of time to corrosion initiation in bridge piers. An empirical model considering the vehicle type, vehicle speed, traffic volume and distance to roadside is used to determine the surface chloride concentration, which in turn is used in the Fick’s second law of diffusion to estimate the corrosion initiation time. The effects of temperature and relative humidity are also considered in this estimation. The proposed method is demonstrated using an example bridge. The effects of vehicle speed, traffic volume, the number of heavy duty vehicles and distance of the bridge substructure to roadside on corrosion initiation time were investigated.]]></description><pubDate>Thu, 04 Feb 2021 10:54:23 GMT</pubDate><guid>http://pubsindex.trb.org/view/1759007</guid></item><item><title>Road Load Based Model for Vehicle Repair and Maintenance Cost Estimation</title><link>http://pubsindex.trb.org/view/1738727</link><description><![CDATA[A techno-economic model is developed based on road-load simulation results expressed in relation to slip energy (SE) at the tire–pavement interface and the repair and maintenance (R&amp;M) cost obtained from published sources and data from state agencies. Tire SE allows for the consideration of aggressive acceleration and deceleration, high torque conditions (for instance, driving an upslope grade), and roadway curvature. Tire SE data used in this effort were generated using physics-based simulation models of different vehicle types for arrays of road conditions (e.g., grades, curvatures) and driving cycles (i.e., vehicle speed profiles). R&amp;M costs were estimated for various vehicle categories and accumulated vehicle mileage. The approach is based on relating the probability density functions (PDFs) of SE and R&amp;M costs. Asymptotic series expansion for an incomplete gamma function was used to approximate the gamma functions and to determine the gamma ratio function that is used as the coefficient to SE to estimate R&amp;M costs. The average R&amp;M cost per mile results from the model compared with the arithmetic mean R&amp;M cost data from fleet operators and published data. The model can serve as a method for predicting R&amp;M cost as a function of road load to vehicle fleet.]]></description><pubDate>Tue, 15 Sep 2020 12:01:29 GMT</pubDate><guid>http://pubsindex.trb.org/view/1738727</guid></item><item><title>Vehicle and Pedestrian Level of Service in Street Designs with Elements of Shared Space</title><link>http://pubsindex.trb.org/view/1722161</link><description><![CDATA[Inspired by developments in urban planning, the concept of “shared space” has recently emerged as a way of creating a better public realm. This is achieved through a range of streetscape treatments aimed at asserting the function of streets as places by facilitating pedestrian movement and lowering vehicle traffic volumes and speeds. The characteristics of streets with elements of shared space point to the conjecture that traffic conditions and road user perceptions may be different to those on streets designed according to more conventional principles, and this is likely to have an impact on the quality of service. The aim of this paper is, therefore, to perform an analysis in relation to level of service (LOS) and to investigate how this may change as a result of the implementation of street layouts with elements of shared space. Using video data from the Exhibition Road site in London during periods before and after its conversion from a conventional dual carriageway to a layout featuring several elements of shared space, changes in relation to LOS for both vehicle traffic and pedestrians are investigated, by applying the corresponding methods from the 2010 Highway Capacity Manual. The results suggest that streets with elements of shared space provide a much improved pedestrian experience, as expressed by higher LOS ratings, but without compromising the quality of vehicle traffic flow, which, in fact, also sees slight improvements.]]></description><pubDate>Thu, 16 Jul 2020 11:02:23 GMT</pubDate><guid>http://pubsindex.trb.org/view/1722161</guid></item><item><title>Predicting Highway–Rail Grade Crossing Gate Violations</title><link>http://pubsindex.trb.org/view/1496707</link><description><![CDATA[This paper uses micro-level vehicle profile data extracted from radar-based sensors to: (1) identify the key variables associated with gate violations at highway-rail grade crossings (HRGCs), (2) develop prediction models for gate violations at HRGCs, and (3) examine the relationship between model accuracy and the key input variables. A data set of 256 vehicle-train events was collected at an HRGC test bed in Lincoln, Nebraska. Among them, 76 events are gate violations and 180 events are non-violations. The vehicle profiles, over a 300 foot distance from the HRGC stop line, were discretized at 10 foot increments. Each increment had 3 variables associated with it. Two tree-based ensemble techniques, the bootstrap forest, and the boosted tree, were applied to determine the relationship among the input variables and the occurrence of gate violation. It was found that once a vehicle is within 190 feet of the HRGC stop line, the model was approximately 80 percent accurate in predicting a gate violation. Influential factors that were identified include speed, time-to-gate, and acceleration over a distance to the stop line. It was found that as the vehicles came closer to the HRGC, and more information was contained in the vehicle profile, the prediction error decreased. It should be noted that with the advent of vehicle profile data collection, the tree-based ensemble techniques are ideal candidates for safety studies because they can utilize the highly non-linear vehicle profiles and relate these to safety surrogate metrics.]]></description><pubDate>Mon, 26 Mar 2018 09:17:17 GMT</pubDate><guid>http://pubsindex.trb.org/view/1496707</guid></item><item><title>Data Processing Framework for Development of Driving Cycles with Data from SHRP 2 Naturalistic Driving Study</title><link>http://pubsindex.trb.org/view/1438857</link><description><![CDATA[In the modeling of vehicle operation costs, a driving cycle is a representative speed–time profile to describe the speed–acceleration pattern of a specific road scenario. Driving cycles are important input for estimation of fuel consumption and polluting emissions. Existing driving cycles are either from out-of-date driving data or without detailed consideration of influencing road properties because of the limitations of available data sets. As part of a project sponsored by FHWA, this research developed a data processing framework for development of driving cycles with data from both the SHRP 2 Naturalistic Driving Study (NDS) and the SHRP 2 Roadway Information Database (RID). The framework included data processing of NDS and RID data and a new synthetic optimization method to generate optimized representative driving cycles. The documented data processing framework was applied to develop the driving cycles of light-duty vehicles for 395 road scenarios with consideration of 10 road properties that could have influenced traffic speed patterns. The 4,400 NDS trips, each of which was at least 20 min long, were used for the development of driving cycles. This data processing frame can be applied for development of driving cycles for more road scenarios with data similar to those in the SHRP 2 database.]]></description><pubDate>Thu, 30 Mar 2017 14:27:38 GMT</pubDate><guid>http://pubsindex.trb.org/view/1438857</guid></item><item><title>Copula-Based Joint Discrete–Continuous Model of Road Vehicle Type and Shipment Size</title><link>http://pubsindex.trb.org/view/1439345</link><description><![CDATA[A major issue in freight modeling is the interrelationship between logistics choices that can be seen as a learning process that shippers or carriers undertake to optimize their logistics process, with the aim of minimizing their cost, maximizing their level of service, or both. This study looked at the interrelated decisions of vehicle type choice and shipment size in urban freight transportation by formulating a model that considered (a) the nature of these two dependent variables via a joint discrete–continuous model, (b) the correlation between the two decisions via a copula-based approach, (c) the differences in decision making between carriers and shippers via the estimation of two models, and (d) the relaxation of the assumption of pure utility maximization via a hybrid utility–regret specification. Results show differences between shippers’ and carriers’ preferences. These differences were logical because many urban shippers owned an efficient fleet of commercial vehicles, whereas carriers evaluated alternatives to maximize their aggregated utility and minimize their direct costs. Results also show the importance of considering jointly the two decisions as well as the relevance of using a hybrid utility–regret formulation for the cost. Practical findings emerge from the model: (a) when faced with night delivery and intercity trips, carriers were more likely to use heavier vehicles and more voluminous shipments, whereas smaller shipments were preferred during the afternoon peak hour; (b) urban shippers tended to deliver larger shipments during night by light trucks but preferred trailers for longer distances; and (c) commodity types played a role in these joint decisions because some commodities were more likely to be transported by for-hire carriers and others were more likely to be transported by shippers.]]></description><pubDate>Mon, 27 Mar 2017 09:33:45 GMT</pubDate><guid>http://pubsindex.trb.org/view/1439345</guid></item><item><title>Real-Time Queue Length Estimation for Signalized Intersections Using Vehicle Trajectory Data</title><link>http://pubsindex.trb.org/view/1438006</link><description><![CDATA[Queue length is one of the most important performance measures for signalized intersections. Many methods for queue length estimation based on various data sources have been proposed in the literature. With the latest developments and applications of probe vehicle systems, cycle-by-cycle queue length estimation based only on probe data has become a promising research topic. However, most existing methods assume that information such as signal timing, arrival pattern, and penetration rate is known, an assumption that constrains their applicability in practice. The objective of this study was to propose a cycle-by-cycle queue length estimation method using only probe data without the foregoing assumption. Based on the shock wave theory, the proposed method is capable of reproducing the dynamic queue forming and dissipating process cycles at signalized intersections by using probe vehicle trajectories. To reproduce the queuing processes, the inflection points of probe vehicle trajectories representing the changes of arrival patterns are identified and extracted from the trajectory points of vehicles joining and leaving the queue. A piecewise linear function is then used to fit all the inflection points to estimate the stopping and discharging shock waves. Finally, signal timing data and queue lengths can be calculated on the basis of the estimated shock waves. Under both saturated and oversaturated traffic conditions, the performance of the method is comprehensively evaluated through 60 simulation scenarios, which cover sampling intervals from 5 s to 60 s and penetration rates ranging from 5% to 100%. Results show that compared with the method proposed by Ramezani and Geroliminis in 2015, the proposed method has more robustness for all the sampling intervals and displays more estimation accuracy of queue length and a higher success rate under conditions of low penetration rate.]]></description><pubDate>Thu, 02 Mar 2017 17:04:04 GMT</pubDate><guid>http://pubsindex.trb.org/view/1438006</guid></item><item><title>Compressed Natural Gas Vehicles: Financially Viable Option?</title><link>http://pubsindex.trb.org/view/1393593</link><description><![CDATA[Natural gas vehicles are being developed because of increasing concerns about energy dependence, air quality and emissions, and, more recently, climate change. The major advantage of natural gas vehicles is their lower fuel cost. Several economic and technical factors such as limited range and availability of relevant infrastructure prevent widespread adoption of natural gas vehicles. A model for the financial analysis of the possibility of compressed natural gas (CNG) vehicles being competitive with gasoline-powered vehicles is offered. The model evaluates the extent to which commuters find adoption of CNG vehicles to be economically viable in the United States. The results indicate that the percentage of commuters who would adopt CNG vehicles is small, even if fueling infrastructure were fully developed and CNG vehicles were widely available for purchase. A larger number of vehicle miles traveled and increased gasoline prices encourage commuters to adopt CNG vehicles, while higher fuel economy and purchase price differentials result in lower adoption rates. In some cases, which vary in accordance with the values of the model’s parameters, commuters purchase a CNG vehicle as their second car and keep a gasoline-powered car as their first.]]></description><pubDate>Mon, 07 Mar 2016 10:46:24 GMT</pubDate><guid>http://pubsindex.trb.org/view/1393593</guid></item><item><title>Estimating Vehicle Shadow Impacts on Solar Irradiation of Roadways</title><link>http://pubsindex.trb.org/view/1394026</link><description><![CDATA[Solar radiation has a significant effect on the snow melt rate in urban areas. The shadows of vehicles reduce the solar radiation on snow surface on streets. Right now, salt application procedures are based on temperature, precipitation and road surface condition without considering incoming solar radiation. In order to ensure quick melting, excess salt is frequently applied. However the price of salt has been rising rapidly. Additionally, salty water running into drains, culvert, streams and rivers can cause many environmental issues. This paper introduces a method to calculate the reduction caused by traffic on solar radiation on streets. Several cities in North America were selected. Based on the latitude and longitude of these cities, vehicles size and the azimuth and elevation of the sun, shadow area of single vehicle was calculated. Based upon the shadow area of single vehicle, traffic volume and traffic population on road, the total reduction on solar radiation on road was calculated. Based on the calculation, future work can be done to adjust the salt application rates to use salt efficiently and to mitigate the environmental issues.]]></description><pubDate>Mon, 29 Feb 2016 16:54:36 GMT</pubDate><guid>http://pubsindex.trb.org/view/1394026</guid></item><item><title>Use of Side Friction in Horizontal Curve Design: A Margin of Safety Assessment</title><link>http://pubsindex.trb.org/view/1393917</link><description><![CDATA[Current engineering practice uses a point-mass model to design horizontal curves on highways and streets. In this model, a maximum side friction factor is used, in combination with the selected design speed and maximum rate of superelevation, to determine the minimum radius of the curve for an alignment. The limiting value for side friction used in design was established in the 1940s and was based on driver comfort thresholds. The lateral friction available at the tire–roadway interface is a measure of friction supply and is dependent on the pavement surface type and condition, vehicle operating speed and deceleration characteristics, vehicle lane position, and tire type. The drivers’ selection of individual operating speeds on a roadway results in a side friction demand when traversing a horizontal curve. The purpose of this paper is threefold. First, key side friction concepts in horizontal curve design are described. This description includes the definitions of and the fundamental principles associated with the application of side friction factors in horizontal curve design policy. Second, the paper provides an analysis of the margin of safety in horizontal curve design policy. This analysis considers various vehicle types, pavement surface types, and operating speed distributions, and makes comparisons between friction supply, demand, and design side friction factors. Third, the paper describes a framework for more effective consideration of the current vehicle fleet, range of pavement conditions, and vehicle speed distribution in horizontal curve design policy.]]></description><pubDate>Thu, 25 Feb 2016 10:15:09 GMT</pubDate><guid>http://pubsindex.trb.org/view/1393917</guid></item><item><title>Synchronization of Public Transport Timetabling with Multiple Vehicle Types</title><link>http://pubsindex.trb.org/view/1392379</link><description><![CDATA[Public transport (PT) timetables play an important role in creating a bridge between the PT agency, the community–municipality, or both and the passengers who seek a reliable, comfortable, and attractive PT service. Inadequate–inaccurate PT timetables not only confuse passengers but also reinforce the unfavorable image of PT service as a whole. Therefore, a prudent timetable strategy can improve these conditions economically and imagewise. This work addresses the problem of PT timetable synchronization while taking into consideration fluctuating passenger demand and multisize vehicle types for better matching of supply and demand. This problem was formulated as an integer programming, two-objective optimization problem. A decomposition method that integrated the route’s headway, vehicle trip offset time, and vehicle type selection and assignment was developed to synchronize timetables of PT routes. The goal was to develop a maximally synchronized timetable that used a mixed-size fleet for a given PT network. The two-objective function was to minimize both the expected total passenger waiting time and the observed passenger load discrepancy at a desired occupancy level on vehicles at the maximum load points. The elaborated methodology was applied to a numerical PT network example and to a real-life PT network in Auckland, New Zealand. The results show that, compared with those of the current timetables, the total passenger waiting time and vehicle load discrepancy can be reduced by 68% to 72% and by 59% to 65%, respectively, by adopting the new timetabling strategy that synchronizes multiple types of vehicles.]]></description><pubDate>Mon, 01 Feb 2016 09:27:39 GMT</pubDate><guid>http://pubsindex.trb.org/view/1392379</guid></item></channel></rss>