Highway Segments Research Articles

Impact of CAV Truck Platooning on HCM-6 Capacity and Passenger Car Equivalent Values

Recently, there has been a significant amount of research related to heavy trucks operating as connected and autonomous vehicles (CAVs). As argued in this paper, to understand the potential impact on the freeway system of CAV technologies, analyses should be conducted using the standard US methodological framework. Consequently, this paper uses the exact Highway Capacity Manual, Sixth Edition (HCM-6) equal capacity passenger car equivalent (EC-PCE) methodology to estimate capacity and EC-PCEs for CAV truck platoons on freeway segments. It was found that EC-PCE values for CAV trucks are, on average, 34.3% lower compared to the values for non-CAV trucks, indicating that CAV platoons can have a positive effect on highway capacity. The amount of decrease is a function of a number of CAV operational assumptions, and these are studied through a sensitivity analysis. This paper demonstrates that the effect of CAV truck platoons can be modeled using the standard HCM-6 approach, and the methodology allows meaningful comparisons so that traffic agencies can better prepare for the adoption of CAV technologies.

Coordinated decisions of discretionary lane change between connected and automated vehicles on freeways: a game theory‐based lane change strategy

Discretionary lane change is an essential part of connected and automated vehicles (CAVs) on freeway segments. Most existing studies were conducted to optimise the individual decision of discretionary lane change of CAVs. However, the effects of motion states and discretionary lane change decisions from the surrounding vehicles via vehicle to vehicle communication were ignored. To address such a problem, a game theory-based lane change strategy is proposed to collaborate and optimise decisions of discretionary lane change between the CAVs. The payoff functions are formulated for three types of decision games and the payoff of each decision is quantitatively calculated considering the state information of surrounding vehicles. The Nash equilibrium is applied to find the optimal decision set for players. A simulation platform of a CAV environment built is used to conduct the simulation experiments. Various metrics are employed to evaluate the proposed strategy, such as total travel delay, surrogate safety measurement and wave number. The results show that the proposed lane change strategy using a game-theoretical approach can effectively improve traffic operation, safety and oscillations compared to the baseline strategy. The proposed lane change strategy can further benefit the implementations of the CAVs.

Lane Group–Based Traffic Model for Assessing On-Ramp Traffic Impact

AbstractOn-ramp merging areas are congestion-prone segments of freeways. Depending on the aggressiveness of the driving population and the congestion level, the speed variance among travel lanes du...

Highway Cost Analysis for Platooning of Connected and Autonomous Trucks

If connected and autonomous vehicles use highways under current lane management policy, only partial benefit can be reaped from the platooning of advanced vehicles. Agencies may have to update the existing policy in the near future because of the regular presence of connected and autonomous vehicles on the highways. The probable management approaches are likely to affect highway construction, rehabilitation, and fuel consumption cost. This paper studied a range of lane management approaches in terms of truck platooning and estimated construction and rehabilitation costs using existing models. It also developed a probabilistic approach of generating varying degrees of vehicle platooning to estimate fuel consumption in a simulated environment of highway segment. The results showed that, compared with a no-platoon approach, most of the approaches considered reduce construction cost but increase rehabilitation cost for a unit length of a highway. Fuel consumption cost decreases due to truck platooning with all possible approaches. If truck platooning is achieved by adding a separate truck-only lane, the fuel consumption benefits are considerably higher.

An efficiency-based capacity formulation: mathematical properties and practical implications

Traditional capacity approaches focus only on the vehicle-carrying ability of a facility; i.e. a freeway segment is characterized by higher speed and volume. Furthermore, these definitions lead to the two-capacity phenomenon which creates confusion among practitioners and researchers over which one is the appropriate value. To address these issues, this paper puts forth a new understanding of freeway capacity by considering the optimal traffic state idea where the infrastructure is operating in the most efficient way. This paper endeavors to explain the existence of the optimal traffic state that may lead to a substantial amelioration of traffic conditions on freeways. These analytical properties are transferable to different families of speed–density models. A simulation study is then undertaken to demonstrate how additional benefits can be achieved using the efficiency-based approach. Results show that the proposed methodology improves the overall traffic network performance in comparison to when conventional capacity is used.

Study of the degree of atmospheric air pollution on a segment of the city highway

The article presents the results of experimental and theoretical studies, as a result of which the impact of traffic organization on the level of air pollution from traffic flows was assessed. The studies were carried out on several sections of one segment of the city highway. The assessment of the state of atmospheric air pollution on a highway with heavy traffic (Mira Avenue, Omsk) was carried out on the basis of determining the content of carbon monoxide (CO) in the air, as one of the main components of the exhaust gases of the traffic flow. Calculations are graphically presented that confirm the unevenness of the amount of pollutant emissions by one passenger car that moves along a segment of a city highway, taking into account several options for traffic regime. Modes of movement are due to the organization of road traffic.

Factors influencing driver behaviour along curved merging interchange terminals

Problem statement. To promote safe and comfortable driving operations, design manuals and policies call for merging terminal ramps to be built along straight roadway sections. However, this prescription may need to be overlooked when there is no alternative to terminals being designed along curves. This study aims to assess the impact of design factors on driver behaviour along curved acceleration terminals with continue or reverse curvature prior to joining the motorway. Methodology. A driving simulation experiment was conducted to observe longitudinal and transversal driver behaviour when certain factors (i.e., radius, ramp length, motorway curve direction, and traffic conditions along the motorway segment) were manipulated. The forty-eight drivers involved were separated into groups based on age and gender. Results. The motorway radius has a significant impact on longitudinal performance, while traffic volume impacts on the merging point where vehicles enter the adjoining motorway lane. Compared to linear terminals, the merging abscissa need to be longer on curved ones so as to compensate for the blind spot and enable drivers to identify and accept gaps between vehicles in the traffic flow. The ramp-terminal connection type influences the speed at the beginning of the terminal, the position of the merging point and transversal driver behaviour. Conclusions. Although some limitations in the study were necessary to limit their impact on the experimental design, the results here may prove useful when considering the adoption of appropriate engineering countermeasures at the design stage of entry terminals along curved motorway segments.

Using PAVER Software to Evaluate Pavement Condition Index of Highway Segment in the North Sector of Najaf City (Case Study)

Current paper present part of comprehensive case study for urban highway networks of north sector of Najaf city located 161 km Southwest of Baghdad the capital of Iraq. The main goals of current paper are to evaluation pavement condition index denoted as (PCI). Values of PCI acting a main factor on depending maintenance of pavement, selecting economic alternative, increasing development of engineers and technician’s capabilities, in order to reach the best maintenance management process and achieve the best riding level with lowest costs and the shortest travel time. PAVER software uses surveying data to calculate pavement condition index which should be within rating from zero, which mean pavement in failed condition, to 100, that mean excellent pavement condition. Pavement’s condition is providing predicting its maintenance and Rehabilitation requirements. Free issue of PAVER 5.2 software was used to calculate values of PCI for a minor arterial urban highway in north sector of Najaf city, that is the Najaf-Karbala highway located from Al-Askarain Tunnel intersection to the end of Al-Nidaa district, with length (8011m). Manual geometric and types of distresses survey was depended instead of using assessment technologies to consider the type, degree of severity, of distresses for sample unites along the highway. As a results of implementing PAVER 5.2 software depending on field survey data collection, PCI value is equal to 80. That’s mean this part of the selected study section was in good situation.

Evaluating the Effect of Incidents on Freeway Facilities and Updating the Incident Capacity Adjustments for HCM

This paper investigates the effect of incidents on freeway segment capacity. Currently, the Highway Capacity Manual (HCM) provides a look-up table linking the remaining segment capacity fraction during an incident to the total and closed number of lanes on the segment. In reality, segment capacity during an incident will tend to vary over time, with the most severe effects felt early on before any type of response is initiated, with congestion progressively improving as the appropriate incident management actions are implemented. By applying a genetic algorithm calibration method on each incident day and calibrating the incident capacity adjustment factors (CAFs), optimal time-dependent CAFs were derived that best represented the effect of incidents on the freeway segment capacity. By analyzing the optimal CAFs, the strongest relationship was revealed to be between the optimal time-dependent CAF and the temporal progression of the incident. A regression model was developed to represent this behavior. This was formulated in a manner that can directly adjust the current HCM’s fixed CAF values (for a specific lane closure configuration) for modeling incidents both in single day, seed file application, or for an entire year reliability analysis. A portion of WB I-540 in Raleigh, NC was selected as the study area in which the proposed method was tested. Between January 2014 and December 2018, the team identified 22 isolated incidents (away from the recurring congestion period) that closed one or two lanes of traffic, creating a distinct congestion pattern.

Extremum Seeking for Traffic Congestion Control With a Downstream Bottleneck

Abstract This paper develops boundary control for freeway traffic with a downstream bottleneck. Traffic on a freeway segment with capacity drop at outlet of the segment is a common phenomenon that leads to traffic bottleneck problem. The capacity drop can be caused by lane-drop, hills, tunnel, bridge, or curvature on the road. If incoming traffic flow remains unchanged, traffic congestion forms upstream of the bottleneck since the upstream traffic demand exceeds its capacity. Therefore, it is important to regulate the incoming traffic flow of the segment to avoid overloading the bottleneck area. Traffic densities on the freeway segment are described with the Lighthill–Whitham–Richards (LWR) macroscopic partial differential equation (PDE) model. The incoming flow at the inlet of the freeway segment is controlled so that the optimal density that maximizes the outgoing flow is reached and the traffic congestion upstream of the bottleneck is mitigated. The density and traffic flow relation at the bottleneck area, usually described with fundamental diagram, is considered to be unknown. We tackle this problem using extremum seeking (ES) control with delay compensation for the LWR PDE. ES control, a nonmodel-based approach for real-time optimization, is adopted to find the optimal density for the unknown fundamental diagram. A predictor feedback control design is proposed to compensate the delay effect of traffic dynamics in the freeway segment. In the end, simulation results are obtained to validate a desired performance of the controller on the nonlinear LWR model with an unknown fundamental diagram.

Collective Risk Ranking of Highway Segments on the Basis of Severity-Weighted Crash Rates

This study is intended to focus on the major factors affecting traffic crash rates and severity levels, in addition to identifying crash-prone locations (i.e., black spots) based on the two indicators. The available crash data for different road segments used for the analysis were obtained from the Washington state database provided by the Highway Safety Information System (HSIS) for the years 2006 to 2011. A Random Forest (RF) classifier was used to predict the outcome level of crash severity, while crash rates were predicted by applying RF regressor. Certain features were selected for each model besides the abstraction of new features to check if there are unobserved correlations affecting the independent variables, such as accounting for the number and weight of crashes within 1 km2 area by implementing the Getis-Ord Gi∗ index. Moreover, to calculate the collective risk (CR) score, crash rates were adjusted to incorporate crash severity weights (cost per severity type) and regression-to-the-mean (RTM) bias via Empirical Bayes (EB) method. Finally, segments were ranked according to their CR score.

Analyzing intra-metropolitan variation in highway traffic performance in Los Angeles using archived real-time data

ABSTRACT We conduct a case study of highway system performance in Los Angeles County. We use the Los Angeles Archived Data Management System, a comprehensive archive of regional real-time multi-modal transportation system data, to analyze effects of systematic, functional, random, and land use factors on performance variation over different time periods of the day. To understand functional class effects, we use cluster analysis on geometric and demand parameters to identify functionally similar groups of highway segments. We compare performance between groups and across segments within groups. We perform regression analysis to test the influence of various factors on performance. We find that after controlling for time of day, accidents, and adjacent population density, group or peer effects have significant influence. This suggests that peer group level, as opposed to regional, performance measurement and monitoring is useful. Our research has significant implications for transportation system monitoring and planning.

Development of a Practical Method to Estimate the Eco-Level of Driver Performance

Motor vehicle’s fuel consumption is one of the main sources of energy consumption in road transportation and is highly influenced by driver performance in the process of driving. Eco-driving behavior has been proved to be an effective way to improve the fuel efficiency of vehicles. Essential to the efforts towards saving vehicle fuel is the need to estimate the eco-level of driver performance accurately and practically. Depending on on-board diagnostics and Global Position devices, individual vehicle’s instantaneous fuel consumption, engine revolution and torque, speed, acceleration, and dynamic location were collected. Back-propagation network was adopted to explore the relationship between vehicle fuel consumption and the parameters of driver performance. Taking 700 data samples in basic segments of urban expressways as our training set and 100 data samples as validation test, we found the optimal model structure and parameters through repeated simulation experiments. In addition to the average and standard deviation value, the fluctuation frequency of driver performance data was also viewed as influence factors in eco-level estimation model. The average estimation accuracy of our developed model has been tested to be 96.37%, which is quite higher than that of linear regression model. The study results provide a practical way to evaluate drivers’ performance from the perspective of fuel consumption and thus give basis for rewarding best drivers within eco-driving programs.

Effect of Distance between Ramp and Upstream Signal on Ramp Meter Operation

Ramp metering is typically proposed as a responsive strategy that takes freeway traffic parameters as control inputs to the ramp control logic. Such a strategy can be implemented in two ways; isolated ramp control or coordinated ramp control. Coordinated ramp control typically involves the cooperation between several ramp meters connected to a freeway segment to manage traffic on the freeway and traffic all ramps. Few studies also proposed the coordination between the on-ramp and the upstream traffic signal. Such coordination can help to mitigate congestion on the freeway and to avoid queue formation at the on-ramp. In this study, the authors' previous work on ramp metering and upstream signal coordination was extended to further evaluate the performance of such schemes by considering the impact of the distance between the upstream traffic signal and freeway. Extensive simulations in SUMO were performed to evaluate the benefit of the proposed coordinated strategy and the impact of ramp distance on the effectiveness of such coordination.

Producing the “Highway to Nowhere”: Social Understandings of Space in Baltimore, 1944-1974

The “highway to nowhere” is a 1.32 mile fragment of an arterial expressway located in Baltimore, Maryland. This segment was designed to contribute to a proposed limited access highway system that was never constructed after years of activism, debate, and lawsuits. This article examines the history of the construction of this highway segment to suggest that conflicts over the design, sitting, and construction of infrastructure are fundamentally struggles over the definition and production of space. This analysis utilizes Henri Lefebvre’s triad of spatial production as an analytical framework to identify distinct spatial forms that surface during the process of infrastructure building. Utilizing this analytical framework may enrich the STS-based infrastructure inquiries by bringing to the surface the multiple forms of spatial production that structure system-building activities. In conclusion, I suggest that utilizing Lefebvre’s triad within studies of infrastructure surfaces important, and potentially transformative, local claims to space. Such claims are of renewed importance as cities across the US confront the segregationist histories of the built environment.

Multivariate models to investigate the relationship between collision risk and reliability outcomes on horizontal curves

This paper proposes a reliability-based framework to address the risk associated with limitations in the Available Sight Distance (ASD) on curved highway segments considering a three-dimensional (3D) sight distance computation approach. To facilitate this assessment, the ASD on horizontal curves was evaluated and an accurate inventory of curve attribute information was generated using LiDAR (Light Detection and Ranging) data in an automated and efficient manner. These datasets were then used to estimate the risk (probability of noncompliance, Pnc) associated with sight distance insufficiencies. Full Bayes multivariate Poisson log-normal safety performance functions were developed to relate the Pnc to the expected number of collisions. The results show that there was a statistically significant relationship between Pnc and collision frequency. There was also a significant correlation of 0.444 to 0.452 across collision severity levels indicating that curves with high Property-Damage-Only (PDO) collisions could be associated with higher injury and fatal (I + F) collisions. It was also found that Pnc had a greater impact on increasing PDO collisions than I + F collisions, suggesting that collisions associated with insufficient sight distance are likely to be less severe. The results of this analysis are expected to improve our understanding of the risks associated with deviations from design guidelines and quantitatively assess the safety margins due to these variations. The framework presented in this paper can be used to compare different design alternatives and investigate the influence of design deficiencies on collision occurrence across various severity levels.

A land-use clustering approach to capturing the level-of-service of large urban corridors: A case study in downtown Los Angeles

Level-of-service has been widely used to measure the operational efficiency of existing highway systems categorically, based on certain ranges of traffic speeds. However, this existing method is generic for investigating urban traffic characteristics. Hence, there is a crucial knowledge gap in capturing the unique traffic speed conditions during a certain temporal duration, in a common spatial area that includes different land use clusters. This study fills this gap by modeling the link between traffic speeds and land use clusters during certain time periods, along with the given level-of-service criteria. As a case study, this study adopted the central business district in Los Angeles in the United States. A total of 1780 traffic sensor speed data on Interstate 10 East adjacent to the central business district of Los Angeles was collected and clustered by the land use designated by the zoning regulations of the city of Los Angeles. The proposed traffic time–speed curve model that integrates different land uses in a large urban core was then developed and validated statistically, using historical real-world traffic data. Finally, an illustrative example was presented to demonstrate how the proposed model can be implemented to measure critical time periods and corresponding speeds per land-use cluster, responding to the designated level-of-service criteria. This study focused on making recommendations for government transportation agencies to employ an appropriate method that can estimate critical time periods affecting the existing operational status of a highway segment in different land-use clusters within a common spatial area, while promoting an effective application of a set of traffic sensor speed data.

Design and Control Method of Switchable On- or Off-Ramp for Urban Highway

High volume of traffic is loaded on urban highway during peak hours as well as the ramp connecting main road and auxiliary road of highway. Once the demand exceeds the capacity of the ramp, congestion may happen on both main road and the auxiliary road. To deal with this problem, an new urban highway ramp, switchable ramp (SR) that can switch between on and off condition, is proposed in this paper. A macroscopic time-space discrete model is built in this paper to model this process by dividing the studied time period into short time periods and the studied road segment into small sections. The impact of the type of ramp on upstream and downstream traffic flow is analyzed. A segment of urban highway in Chengdu, China, is used as a case study. The traffic flow data in peak hours is collected and used. Mathematical analysis proves that the SR system proposed in this paper can reduce the total travel time (TTT) in the studied area. Results show that the SR system is more useful when the traffic volume is high.

Multiple correspondence analysis applied to the study of the relationship between traffic crashes and precipitation on a highway in Brazil

A incorporação de dados meteorológicos em pesquisas envolvendo o estudo de acidentes é considerada como essencial quando se objetiva analisar o comportamento de acidentes rodoviários. Neste contexto, o presente trabalho pretendeu explorar a existência de correlação entre ocorrência de acidentes rodoviários e condições climáticas, em específico a precipitação diária, num trecho selecionado da Rodovia BR- 376 (Paraná, Brasil). Uma análise de correspondência múltipla (ACM) foi aplicada (software Statigraphics) para determinar a relação existente entre as características dos acidentes e a precipitação. A ACM permitiu a criação de um mapa perceptual, agrupando as variáveis consideradas semelhantes de acordo com o método, o qual evidenciou que a intensidade da chuva não foi um fator significativo para alterar as características dos acidentes. Entretanto, a ocorrência de precipitação mostrou-se como uma circunstância condicionante. Com respeito à segurança da rodovia, a pesquisa indica aplicações práticas que podem ser aplicadas pelas agências de tráfego, como a implementação de sinalização de tráfego e educacional em pontos específicos da rodovia.

Factors associated with traffic crashes on urban freeways

The majority of earlier works suggested that traffic fatalities in a rural section of highways are relatively higher than those observed in urban areas. However, the recent report released by the National Highway Traffic Safety Administration (NHTSA) described the trend that the urban area highway fatalities in the last four years are higher than the crashes that occurred on a rural section of the highway segments. In the present work, the key factors influencing fatal, non-fatal injury and property damage only crash on four and six-lane urban interstate highway segments are analyzed. A negative binomial regression approach was used for the analyses of the three crash categories, and a meaningful statistical interpretation of the developed model estimates are provided in terms of the incident rate ratio. The results of the study suggest that traffic volume, median type, and the number of lanes were factors associated with fatal, non-fatal injury, and property damage only crashes. All the categories of the horizontal and vertical geometries of the roadway segment were found to be critical factors influencing property damage only crashes. The results also showed that the effect of drivers’ gender was insignificant across the three crash categories.