Two-lane Roads Research Articles

Estimating the Probability That a Vehicle Reaches a Near-Term Goal State Using Multiple Lane Changes

This paper proposes a model to estimate the probability of a vehicle reaching a near-term goal state using one or multiple lane changes based on parameters corresponding to traffic conditions and driving behavior. The proposed model not only has broad application in path planning and autonomous vehicle navigation, it can also be incorporated in advance warning systems to reduce traffic delay during recurrent and non-recurrent congestion. The model is first formulated for a two-lane road segment through systemic reduction of the number of parameters and transforming the problem into an abstract statistical form, for which the probability can be calculated numerically. It is then extended to cases with a higher number of lanes using the law of total probability. VISSIM simulations are used to validate the predictions of the model and study the effect of different parameters on the probability. For most cases, simulation results are within 4% of model predictions, and the effect of different parameters such as driving behavior and traffic density on the probability match our expectation. The model can be implemented with near real-time performance, with computation time increasing linearly with the number of lanes.

Right-of-way reallocation for mixed flow of autonomous vehicles and human driven vehicles

Autonomous Vehicles (AVs) are bringing challenges and opportunities to urban traffic systems. One of the crucial challenges for traffic managers and local authorities is to understand the nonlinear change in road capacity with increasing AV penetration rate, and to efficiently reallocate the Right-of-Way (RoW) for the mixed flow of AVs and Human Driven Vehicles (HDVs). Most of the existing research suggests that road capacity will significantly increase at high AV penetration rates or an all-AV scenario, when AVs are able to drive with smaller headways to the leading vehicle. However, this increase in road capacity might not be significant at a lower AV penetration rate due to the heterogeneity between AVs and HDVs. In order to investigate the impacts of mixed flow conditions (AVs and HDVs), this paper firstly proposes a theoretical model to demonstrate that road capacity can be increased with proper RoW reallocation. Secondly, four different RoW reallocation strategies are compared using a SUMO simulation to cross-validate the results in a numerical analysis. A range of scenarios with different AV penetration rates and traffic demands are used. The results show that road capacity on a two-lane road can be significantly improved with appropriate RoW reallocation strategies at low or medium AV penetration rates, compared with the do-nothing RoW strategy.

A hazard-based model of the motorcyclists’ overtaking duration

The overtaking maneuver performed by motorcyclists is one of the primary causes of motorcycle accidents. However, few studies in the literature deal with this topic and there are no studies modeling the total overtaking duration, i.e. the time during which extreme hazards are manifest. The present paper aims to analyze the motorcyclists’ behavior during overtaking and to model the total overtaking duration. A field experiment, using instrumented motorcycles, was performed to collect data and a survival analysis was carried out to model the total overtaking duration. Twenty young motorcyclists drove their own motorcycles, which were instrumented with a camera and a global positioning system device (GPS), onto a two-lane suburban road in Rome. A total of 101 overtaking maneuvers were recorded. A methodology, based on video and GPS analyses, was developed to obtain data describing the motorcyclists’ behavior. The obtained results showed that the mean values of the main parameters of the overtaking maneuver (total overtaking duration - 6.6 s - and distance - 109.7 m - lateral distance from the passed vehicle - 1.50 m) were consistent with the few data available in the revised literature. The total overtaking duration was modelled using a hazard-based duration model. The parametric accelerated failure time duration model with a log-logistic distribution, which was the best-fitted distribution, identified the covariates which affected, in a statistically significant way, the total overtaking duration. The obtained model revealed that the overtaking duration depends on several covariates. The greater average impact was found for the initial distance and speed difference, while the initial lateral distance and final distance produced a minor impact. When performing a multiple overtaking, the duration of the maneuver tended to increase by 31 %. This research can be considered as a pilot study and a starting point for future advances on motorcyclists’ behavior during overtaking maneuver and for modeling the total overtaking duration. In addition, the findings of this study could contribute to the development of advanced rider assistance systems for the overtaking maneuver based on current driving conditions.

Investigation of the overtaking and overtaken vehicles speeds on two-lane roads in the traffic conditions of the Russian Federation

The speeds investigation results of the overtaking, overtaken and moving on the opposite lane vehicles on two-lane roads in the conditions of the Russian Federation are presented in this paper. The investigations were carried out using unmanned aerial vehicles in compliance with generally accepted scientific methods. Based on the statistical processing of the measurement results, generalized vehicles speed data within the overtaking sections was obtained. It was noted that the presented investigations may be a rationale for improving the requirements for the design of roads on the territory of the Russian Federation. In addition, the obtained data may be used to develop measures to improve traffic safety on existing roads, which will have a generally beneficial effect on traffic safety.

Analysis of Road Safety in Poland after Accession to the European Union

The article presents an assessment of the state of safety on Polish roads in the period 2004-2018 in terms of changes that occurred after Poland’s accession to the EU. The number of vehicles in the period in question was analyzed and the annual growth of the number of vehicles of the main types was assessed. Analysis of changes in the length of the most important road types was carried out. The number of accidents and fatalities was analyzed and the changes in this area were assessed. The statistical decrease in the number of accidents and fatalities, as well as a very strong correlation between them, were confirmed. It was indicated in which groups of accidents the fatality risk is the highest. The paper presents a summary of the types of roads on which traffic accidents and fatal traffic accidents occurred. Shares of these roads were determined, indicating that the most dangerous roads in Poland are the two-way, two-lane roads.

Comparison of the highway safety manual predictive method with safety performance functions based on geometric design consistency

Road safety is a major public health concern in our society. Effective road design and accurate safety analyses must be a component of programs focused on reducing and eliminating roadway injuries and deaths. Various methodologies exist to determine the expected number of crashes on rural two-lane rural roads. This research compares different procedures which allow for the estimation of the number of crashes on homogeneous road segments. In this effort, a total of 27 two-lane rural road sections located in North Carolina were considered, resulting in 59 homogeneous road segments composed of 350 horizontal curves and 375 tangents along 150 km of road. Four methods were applied to the selected roadways: the Highway Safety Manual predictive method, two jurisdiction-specific Safety Performance Functions (SPFs), and a SPF which includes a consistency parameter. This research found that the use of SPFs which incorporate a consistency parameter allows highway engineers to consider human factor impacts on road safety assessment. The use of a consistency parameter can also simplify the crash estimation process. Analysis methods which only included local geometric variables provided unreliable results due to the calibration of only the specific road elements instead of their relationship with other road elements along homogeneous road segments.

The effect of anisotropy on the traffic flow behavior: Investigation of the correlation created by a single node on two-lane roads

In this paper, we have tried to point out the features of the correlation between the lanes of a two-lane road, created by the entry of this facility. For this purpose, we have adopted a quasi-one-dimensional system composed of a diverging node connecting two roads and where no lanes’ changing is allowed. Our study has highlighted the strong effect of a node. We have found that if we create a disturbance in one lane, a spontaneous symmetry breaking occurs in the whole system. In fact, a self-anisotropy is produced at the node, to which the system responds via a self-organization mechanism. Those results have urged us to investigate the anisotropy as an extrinsic parameter. By privileging one lane over the other at the node, we have been able to confirm that the system can always get self-organized and that three phases can be established: the symmetric high density phase, the asymmetric low density phase and the asymmetric phase of transition low density/high density. Finally, we have found that the system is strongly correlated when it is in a symmetric phase, and is not when in an asymmetric phase. This finding brought us to the assumption that the cross-correlation of the observables of a quasi-one-dimensional system can be considered as an order parameter that defines the phases’ transitions.

Investigation into passing behavior at passing zones to validate and extend the use of driving simulators in two-lane roads safety analysis

A passing maneuver allows drivers to maintain their desired speed on two-lane highways. However, it entails a high risk of collision with vehicles travelling in the opposite direction. Investigating drivers’ behavior while performing passing maneuvers could provide helpful information on the factors that influence this process. Driving simulators have become important tools for driving behavior research studies as they are safe, facilitate the controlled use of experimental variables, and generate detailed output data. It remains to be seen whether simulator results can be considered representative of real-life driving conditions. With respect to passing maneuvers, no study has made a comprehensive and direct comparison between drivers’ passing behavior in the field and driver behavior observed in a simulated environment.In this validation study, a fixed-base interactive simulator was used to collect data from fifty-four participants (eighteen Iranians and thirty-six Italians) involved in several traffic scenarios on a two-lane rural highway segment (obtained by varying the speed of opposing vehicles, lead vehicles and headways in the opposite direction). A 3D model and its environmental characteristics were realized from the real segment which had previously been surveyed with drones to collect videos and derive data on real passing maneuvers.The results for the two-sided K–S test revealed no statistically significant difference in the accepted gap, effective accepted gap, perception reaction time, and time to collision variables between the field and the simulator at the 95 % confidence level. However, when conducting a one-sided K–S test, some statistical directional differences were found in the cases of the accepted gap and perception reaction time variables, which exhibited lower values in the field compared to the simulator again at the 95 % confidence level. Although the passing duration was statistically higher in the simulator than in the field, the shape of the two distributions was not statistically different. Analysis showed that differences in the passing duration are due to the lower passing vehicle speed and lower speed difference with the simulator than in the field, which are caused by truncating headways in the subject direction in the simulator. The cultural background of participants did not result in any discernible difference in passing behavior. The results would support a more extensive use of driving simulators in future passing behavior studies.

IRI Performance Models for Flexible Pavements in Two-Lane Roads until First Maintenance and/or Rehabilitation Work

Pavement performance models play a vital role in any pavement management system. The Regional Government of Biscay (RGB) (Spain) manages a 1200 km road network and conducts pavement data collections, including the International Roughness Index (IRI) values. The aim of the paper is to develop an IRI performance model for two-lane roads with flexible pavement until the first maintenance and/or rehabilitation activity is performed. Due to the huge amount of available information, a deterministic model was selected. A literature review of deterministic models showed that, apart from age and traffic volumes, the pavement structure is a key factor. Therefore, it was decided to analyze the only road stretches whose entire pavement section was known (surface layer + base + subbase). Various variables related to age, traffic volumes and employed materials were introduced as possible factors. The multiple linear regression model with the highest coefficient of determination and all the variables significant included the real pavement age, the cumulated heavy traffic and the total thickness of bituminous layers. As the material employed in the surface layer could affect roughness progression, a qualitative variable was introduced to consider various surface materials. The model improved its accuracy, indicating that the surface layer material is also an influencing factor on IRI evolution.

Geometric Design Issues and Safety Analysis of Two-way Rural Road Tunnels

Rural road tunnels may pose specific issues from several perspectives: mainly environmental, geotechnical/structural (excavation methods), economical. Geometric road design is then an often arduous task, which should be conducted by trying to make trade-offs between the different issues, and at the same time, it should be compliant to relevant standards and regulations. Nevertheless, the safety of road tunnels should be preserved, not only considering technological systems (e.g. ventilation systems, emergency exits and paths), but also regarding traditional road-safety issues related to road geometric features. In fact, the analysis of recent accident data related to two-way two-lane rural road tunnels has revealed that accident frequencies/rates in two-way two-lane rural road tunnels are comparable with those on the corresponding open sections, even with some differences concerning the accident types. Since road safety issues may be exacerbated by geometric design inaccuracies, some relevant road tunnel geometric issues are discussed in this study. These issues, scarcely treated in previous research and not addressed in detail in technical documents, emerge from the match between different design needs. In detail, those relate to: 1) the possible need for variable road tunnel cross-sections in case of lane/shoulder widenings for the sake of improving visibility or for other reasons, or in case of lay-bys, 2) the possible need for climbing/overtaking lanes in case of steep downhill or uphill slopes. An attempt at addressing the mentioned problems is provided, based on relevant existing research and technical documents. In particular, the preliminary design stages leading to a “WES” (Without Enlargement Solution) solution are described. Hence, besides enlarging the research body in this specific field, the study is also potentially deemed useful for practitioners who have to face similar design problems.

Capacity estimation on two lane hilly roads under heterogeneous traffic condition in India

Most of Indian National and State Highway system comprises of two-lane highways. Two-third length of National Highways and more than 50 percent length of State Highways are still two-lane roads. Roadway factors that influence capacity of a two-lane road include lane width, gradient, lateral clearance, width and type and condition of shoulder. Realizing that grade magnitude (%) is one of the important and less researched roadway factor in India, the present study principally aims at estimating capacity on two-lane undivided hilly roads under prevailing heterogonous traffic conditions. In the present study, four different study sections with varying magnitude of gradient (2% to 7%) are selected between Saputara and Waghai town, area in the State of Gujarat, India. The magnitude of grades of selected roadway sections is found to be in the range of 2% to 7% Fundamental diagrams are developed employing Geenshield’s model for four different sections for estimating capacities using 5-minute flow rate values along with other macroscopic parameters. The study shows that capacity values developed are realistic and consistent with the values given in Highway Capacity manual (HCM) of developing countries like Indonesia and China. Capacity value and operational speeds of vehicles are significantly influenced by various factors like roadway geometry, roadway condition, traffic conditions, etc. Therefore, as an application of the study, the present study proposes a novel approach of developing relationships (i) capacity versus operating speed of cars, and (ii) capacity versus gradient magnitude (%) based on the observed traffic data sets. It is expected that the results may be very useful for the practitioners and for ongoing efforts of developing Indian Highway Capacity Manual.

Operational Evaluation of Climbing Lanes on Steep Grades and Heavy Trucks

Nearly 99% of Colombian roads have two lanes. In order to improve their level of service (LOS), they have been turned into multilane roads through the doubling of existing highways without technical criteria to justify such transformation, and without considering more appropriate alternatives such as auxiliary lanes. Due to Colombia’s mountainous topography and the high weight/power ratio of the vehicles in circulation, research on auxiliary lanes has been carried out to clarify their applicability. However, operational evaluation procedures such as the Highway Capacity Manual (HCM) may not be representative for the infrastructure and vehicles in Colombia.The hypothesis is that the operational benefits of climbing lanes on two-lane roads with Colombian infrastructures and trucks are higher than the HCM estimate. The objective is to carry out an operational evaluation of the effect of auxiliary lanes on traffic in 84.000 scenarios, and to determine threshold values of operational indicators in order to provide guidance for a better design of this kind of infrastructure.The operational analysis was performed on a virtual road with an auxiliary lane with Colombian trucks and a variety of road geometry and traffic features. Traffic operations were simulated with TWOPAS, part of the Interactive Highway Safety Design Model (IHSDM), for which the computational program PEMAT was created. The results demonstrate the benefits of auxiliary lanes on the improvement of Percent Time Spent Following (PTSF) and Average Travel Speed (ATS), and define criteria for geometric design.

Influence of Safety in Performance Assessment of Two-Lane Highways: A Critical Review

Traffic operations on two-lane roads are different from that of multilane roads because of the presence of opposing traffic. More often than not, faster vehicles get impedance from slower ones, entrapped inside platoons and delayed. The delay caused to these vehicles depends on both the flow of traffic and the proportion of slower vehicles in its composition. Drivers’ of delayed vehicles search for an acceptable gap to perform passing operations. At times, a part of drivers becomes reluctant to move in platoons, especially when such delay is long enough, and they start exhibiting risk-taking behaviour while passing impeding slower vehicles. Such attempts significantly affect operations and safety of traffic. The problem is, however, more acute when the prevailing traffic is heterogeneous with a sizable proportion of slower vehicles. The present study, thus, elucidates the need for considering both operation and safety in the performance assessment of two-lane two-way highways under such traffic situations.

Geometric and Operational Features of Horizontal Curves with Specific Regard to Skidding Proneness

(1) Run-off-road (ROR) crashes are a crucial issue worldwide, resulting in a disproportionate number of traffic deaths. In safety research, macro-level analysis on large datasets is usually conducted by linking explanatory variables to ROR crash frequency/severity. Micro-analysis approaches, like the one used in this study, are instead less frequent. (2) A comprehensive Italian Fatal + Injury (FI) crash dataset was filtered to identify two-way two-lane rural road curves on the national road network on which more than one ROR FI crash (i.e., at least two crashes) in the observation period of four years had occurred. The typical features of the ROR FI crashes and the recurrent geometric (characteristics of tangents and curves) and operational features (inferred speeds, acceleration/decelerations) of the crash sites were reconstructed. (3) The main contributory factors in ROR FI crashes are: wet pavements, speeding, and distraction. Sites with a relevant history of ROR FI crashes present recurrent safety issues such as inadequate horizontal curve coordination, an insufficient tangent length for decelerating, and inferred operating speeds comparable/higher than the inferred design speeds. (4) Based on findings, some practical suggestions for road safety management and maintenance are proposed through specific indicators and countermeasures (speed, perception, and friction related).

Manipulating constraints on driver-cyclist interactions in a fixed travel space: Effects of road configuration on drivers’ overtaking behavior

The effect of road configuration on drivers’ behavior when overtaking cyclists has mainly been investigated in the field by measuring the leeway left by motorists at the time of passing (i.e., lateral clearance) without controlling for the driver’s travel space (i.e., distance between the centerline and the cyclist). The aim of the present driving-simulator study was to determine whether manipulating the configuration of two-lane rural roads in a fixed travel space would affect driver overtaking on tangents. The lane width, shoulder width, and the cyclist’s position were manipulated. Driver overtaking behavior was analyzed by measuring lateral clearance, passing speed, and the frequency of near passes (<1 m) and centerline encroachments. The results showed that variations in the driver’s travel space brought about by different lane widths and cyclist positions had a significant impact on lateral clearance, highlighting the importance of controlling this factor to gain insight into the influence of road design on overtaking behavior. It was also found that shoulder widening in constant travel-space conditions was ineffective in altering driver-cyclist interactions. Finally, manipulating road configuration in a fixed travel space and pavement width did have an impact on lateral clearance, without affecting the passing speed or the frequency of centerline encroachments. Overall, these findings have implications at the methodological level for future studies on driver-overtaking behavior, and at the applied level for the design of shoulders and the configuration of two-lane rural roads suitable for cycle use.

Design Criteria for Improving Safety Performance of Rural Intersections

This paper, on the one hand, aims to identify significant crash risk factors at unsignalized three-leg intersections connecting rural two-lane two-way roads and minor roads with a STOP control on the approaches (3ST) and, on the other, to make adjustments to the Highway Safety Manual (HSM) procedure, fine-tuning its Safety Performance Function (SPF) based on observation of the local context. Over an 8-year period of study, a total of 240 crashes on 35 3ST intersections were observed, with no geometric-infrastructure adjustments or changes in the Annual Average Daily Traffic (AADT) and surrounding context noted at the intersections investigated. To obtain reliable results, the study period was divided into two groups: (a) 5 years to calibrate a new SPF, and (b) the remaining 3, not included in the first dataset, were used to validate the results. A negative binomial regression model was adopted to calibrate the new SPF. It was found that the AADT on the major and minor roads, the intersection skew angle, the co-occurrence of left and right-turn lanes on the major roads, and lighting seriously affect the crash scenario.

Outdoor Visible Light Communication in Intelligent Transportation Systems: Impact of Snow and Rain

A comprehensive study of outdoor visible light communication (VLC) under snow and rain effects has been conducted in this paper. This paper analyzes the expected rain attenuation of Marshal, Carbonneau, and Japan models at different precipitation levels. Snow attenuation is measured in wet and dry situations at various precipitation levels as well. Therefore, a full comparison is carried out for different attenuation effects on certain outdoor VLC design characteristics such as the maximum signal-to-noise ratio (SNR), optical power received, bit error rate (BER), and maximum coverage area. VLC with various modulation techniques is considered. The ON–OFF Keying (OOK), L-Pulse Position Modulation (L-PPM), Inverse L-Pulse Position Modulation (I-L-PPM), and Subcarrier Binary Phase-Shift Keying (SC-BPSK) are investigated. The simulation results show a considerable difference in the information received under different weather conditions depending on the type of modulation scheme used. The simulation has been done on a two-lane road, and a green traffic light-emitting diode (LED) with a wavelength of 505 nm is used as a transmitter. A non-imaging concentrator coupled with a photodetector is considered to be a cost-effective receiver.

Mixed flow of autonomous and human-driven vehicles: Analytical headway modeling and optimal lane management

Presence of autonomous vehicles (AVs) affects traffic flow characteristics of a mixed traffic stream comprising human-driven vehicles. To model the impact of AVs on the saturation flow of arterials and highways, we propose analytical models to derive the expected value and variance of headway of a traffic stream with mixed AVs and conventional human-driven (or normal) vehicles (NVs), given the expected penetration rate of AVs. The proposed model considers the arrangement (order) of AVs and NVs in the mixed stream and the expected, the lowest, and the highest achievable headways and their variability are analytically derived. Moreover, the total delay of a two-lane road with interrupted traffic flow is analytically modeled for various possible lane allocation policies: (a) dedicated lanes, (b) mixed-mixed lanes, (c) mixed-NV lanes, and (d) mixed-AV lanes. Microsimulation experiments demonstrate the validity of the developed models for the average headway and its variability, as well as the delay formulas.

Performance of a Low-Height Acoustic Screen for Urban Roads: Field Measurement and Numerical Study

Field measurements and numerical modelling were used to study the acoustic performance of a low screen in an urban road setting. The results show the usefulness of low screens as well as suggests improvements in screen design. For the measurements, an acoustic screen built up from concrete modules was temporarily installed beside a small park on the reservation between a two-lane road and a track for walking and cycling. A larger traffic system, of which the two-lane road is a part, determines the daytime equivalent noise level within the urban area. The screen height was about 1.4 m as measured from the level of the road surface and the width of the screen top was 0.3 m. Measurements were carried out both at 20 m distance from the road (within the park) and at 5 m distance from the road (at the cycle track). Insertion loss in maximum level, using controlled lightvehicle pass-by at 50 km/h, was measured to 10 dB at 5 m distance and to 6 dB at 20 m distance, at 1.5 m height. Insertion loss in equivalent level was measured within the park to 4 dB at 1.5 m height. A listening experiment confirmed a perceived improvement from installing the screen. The measured results were also compared with predicted results using a boundary element method (BEM) and a noise mapping software, the latter showing good agreement, overestimating the equivalent level insertion loss by 1 dB in the park. The BEM comparison showed reasonable agreement in maximum level insertion loss considering that facade reflections were excluded, with an overestimation of 5 dB at the cycle track, and good agreement in the park, overestimating by up to 1 dB the equivalent and maximum level insertion losses. BEM predictions were used to also investigate other screen designs, showing a positive effect of an acoustically soft screen top, significant for a screen width of 0.2 m and increasing for wider screens.

Traffic Simulation Analysis on Running Speed in a Connected Vehicles Environment

Connected vehicles (CVs) exchange a variety of information instantly with surrounding vehicles and traffic facilities, which could smooth traffic flow significantly. The objective of this paper is to analyze the effect of CVs on running speed. This study compared the delay time, travel time, and running speed in the normal and the connected states, respectively, through VISSIM (a traffic simulation software developed by PTV company in German). The optimization speed model was established to simulate the decision-makings of CVs in MATLAB, considering the parameters of vehicle distance, average speed, and acceleration, etc. After the simulation, the vehicle information including speed, travel time, and delay time under the normal and the connected states were compared and evaluated, and the influence of different CV rates on the results was analyzed. In a two-lane arterial road, running speed in the connected state increase by 4 km/h, and the total travel time and delay time decrease by 5.34% and 16.76%, respectively, compared to those in the normal state. The optimal CV market penetration rate related to running speed and delay time is 60%. This simulation-based study applies user-defined lane change and lateral behavior rules, and takes different CV rates into consideration, which is more reliable and practical to estimate the impact of CV on road traffic characteristics.