Auxiliary Lane Research Articles

An approach for evaluating traffic safety of expressway weaving segments: Investigating risk patterns of lane-changing conflicts

Weaving segments, integral to expressway systems, face safety challenges due to frequent lane changes. While previous research has leveraged pre– and post–lane-changing (LC) data for risk estimation, few efforts have assessed time-series characteristics of LC conflict risks. This study proposes an approach to evaluate safety performance of weaving segments by investigating conflict risk patterns during the LC process using vehicle trajectory data. First, risk profiles are generated based on driving safety field theory for detected LC conflicts. These profiles are then categorized into distinct time-series patterns using k-shape clustering. Finally, determinants of these patterns are identified by enhanced random forest, which provides valuable insights into their relationship with risk severity. Analysis of trajectory data from 12 weaving segments in China reveals three main risk patterns (ascent, descent, and stabilization with a peak) for both rear-end and sideswipe conflicts. Ascending risk patterns signify more severe conflicts compared to descending ones. Increasing auxiliary lanes at weaving segments results in a more evenly distributed acceleration, potentially leading to a more severe LC conflict. The lowest risk is observed at the weaving segments with two auxiliary lanes. This study offers a novel perspective for mitigating LC crashes and enhancing traffic safety in weaving segments.

Connected Automated and Human-Driven Vehicle Mixed Traffic in Urban Freeway Interchanges: Safety Analysis and Design Assumptions

The introduction of connected automated vehicles (CAVs) on freeways raises significant challenges, particularly in interactions with human-driven vehicles, impacting traffic flow and safety. This study employs traffic microsimulation and surrogate safety assessment measures software to delve into CAV–human driver interactions, estimating potential conflicts. While previous research acknowledges that human drivers adjust their behavior when sharing the road with CAVs, the underlying reasons and the extent of associated risks are not fully understood yet. The study focuses on how CAV presence can diminish conflicts, employing surrogate safety measures and real-world mixed traffic data, and assesses the safety and performance of freeway interchange configurations in Italy and the US across diverse urban contexts. This research proposes tools for optimizing urban layouts to minimize conflicts in mixed traffic environments. Results reveal that adding auxiliary lanes enhances safety, particularly for CAVs and rear-end collisions. Along interchange ramps, an exclusive CAV stream performs similarly to human-driven ones in terms of longitudinal conflicts, but mixed traffic flows, consisting of both CAVs and human-driven vehicles, may result in more conflicts. Notably, when CAVs follow human-driven vehicles in near-identical conditions, more conflicts arise, emphasizing the complexity of CAV integration and the need for careful safety measures and roadway design considerations.

Study on the Rationality of Lane Imbalance Design in Freeway Diverging Areas

Currently, a lane imbalance design scheme without auxiliary lanes for two-lane exits is increasing. To study the rationality of this exit scheme, the relationship between lane balance and traffic efficiency in the diverging area is investigated using a drone and image recognition software. The Kalman filter is used to optimize the original data and simplify the process of extracting the traffic volume, density and speed by Frenet coordinate transformation. Under the three states of free flow, saturated flow and supersaturated flow, lane balanced exit and lane imbalanced exit simulation models were constructed by using VISSIM. Based on the traffic flow theory, the curve of the relationship between traffic volume and density was fitted. The traffic volume corresponding to the difference between two schemes at the same density not exceeding 5% or 10% is calculated, and this traffic volume is defined as the scheme selection limit value. The results show that the traffic efficiency of lane imbalance scheme is consistently lower than that of lane balance scheme under all traffic conditions at the freeway exits. However, the difference in traffic efficiency between the two schemes is not fixed but increases as the upstream input traffic volume increases. When the exit forecast service traffic volume is lower than the “ scheme selection limit value ” (SSLV), the difference in traffic efficiency between the two schemes will not exceed 5% or 10%. In conclusion, the lane imbalance scheme can be used in the diverging area under certain traffic volume conditions, thus reducing the land, engineering volume and cost requirements. It also provides ideas for the study of three-lane exit ramp design schemes.

A surrogate safety analysis at sharp gore areas of diverging freeway ramps using micro simulation under congested traffic conditions

Safety at the gore areas near diverging ramps is very crucial during planning and implementation of highway safety improvement programs. Limited research has been conducted on safety at the gore areas on arterial roads. This study aims at investigating the impact of improving a sharp gore area in Lincoln, Nebraska by performing a micro simulation before-and-after study with respect to its underlying state of safety and congestion. Data on travel times and traffic volumes for peak hours are incorporated after successful calibration to find out how a geometric intervention can decrease mobility issues as well as the likelihood of crash involvement. This study has utilized VISSIM software package to run the simulation however, to perform safety analysis, Surrogate Safety Assessment Model (SSAM) is used which is developed by the Federal Highway Administration (FHWA). During the model calibration, custom driving behaviors are created to represent driving tendencies of familiar drivers. The simulation results indicated that by adding an auxiliary lane near the gore area, the mobility issues such as bottle necks, lane changing dilemmas and queue lengths are substantially decreased. However, geometric interventions such as provision of a separate lane, increasing ramp spacing, nose spacing, deceleration area and queue storage area considerably reduced the likelihood of rear-end and lane changing crashes. Surrogate safety assessment in diverging ramps, particularly for sharp gores, has not previously been studied, and this study can serve as a primary footmark for future research on ramp-gores safety.

On gap matching for lane-changing vehicles: Coordinated strategies to improve traffic flow at weave bottlenecks

The weaving section on the freeway will be an active bottleneck due to vehicles’ mandatory or discretionary lane-changing (LC) conflicts. In the early stages of the development of intelligent connected transportation, destination information collection of weaving vehicles is possible, which provides an opportunity to improve performance in weaving traffic. In this paper, a simulation system with coordinated strategies embedded to satisfy the LC needs is presented under the weaving traffic flow. First, an algorithm is proposed to evaluate the balance between the demand for LC vehicles and the available gaps provided in weaving traffic, which can be adjusted by variable speed limit (VSL) and ramp metering strategies. Second, to validate the proposed algorithm, a typical weave section with a merge and a diverge connected through a single auxiliary lane is researched, and a simulation platform based on cellular automata has been developed. The optimal control strategies are obtained by model predictive control (MPC) and taking the minimum travel time as an objective. Third, the advantages of coordinated control strategies are studied and discussed in traffic efficiency improvement and the success of LC proportions under different combinations of weaving ratios and large vehicle traffic mix.

Speed behaviour and mental workload of small-spacing expressway interchanges based on field driving test

Many small-spacing interchanges (SSI) appear with the improvement of the expressway network. To investigate the speed and mental workload characteristics in the SSI and acquire the mechanism of the influence of speed on the drivers’ workload, 37 participants were recruited to perform a field driving test. Each driver performed four driving conditions (i.e. ramp-mainline, mainline-ramp, mainline driving, and auxiliary lane driving). The speed and drivers’ electrocardiogram (ECG) data were collected using SpeedBox speed acquisition equipment and PhysioLAB physiological instrument. The heart rate increase (HRI) index was used to analyse the drivers’ mental workload regularity. The relationship model between speed and HRI was developed to examine the impact of speed on HRI. The results show that the speed variation in the SSI displayed two patterns: ‘decrease - increase and continuous decrease.’ The drivers’ HRI variation presented four patterns: ‘convex curve, continuously increasing, continuously decreasing and concave curve’. SSI's influenced area length is given based on the speed and HRI variation regularity. HRI is significantly higher when driving in the ramp-mainline condition in the SSI than when driving in other conditions, indicating that drivers are more nervous when merging with the mainline traffic. HRI increases significantly in the first 50% of the weaving area in four driving conditions, indicating that vehicle weaving greatly influences the drivers’ mental workload. A positive correlation exists between vehicle speed and drivers’ HRI without interference from other vehicles and road alignment.

Research on Efficient Operation for Compound Interchange in China from an Auxiliary Lanes Configuration Aspect

Interchanges are the key nodes of the freeway. Due to the existence of weaving behavior, the traffic flow situation is more complicated for small spacing interchanges. Continuous auxiliary lanes are usually used to connect the entrance and exit to form a compound interchange to reduce the interference of weaving behavior. However, when it comes to the design of auxiliary lane forms, China lacks relevant design specifications and research in this area. As a result, there often exists the phenomenon of mismatch between the design form and the traffic volume. In this paper, we took a compound interchange in Xi’an as the research object, proposing four auxiliary lane design schemes and using VISSIM (2022 student) software to establish the simulation model. Additionally, various traffic conditions were simulated through sensitivity analysis. Finally, using the factor analysis method and entropy method, we comprehensively assigned weights to the indexes. By obtaining the weighted scores for various schemes, it became possible to determine the applicability of each scheme under different traffic conditions. The results indicate that the gradient auxiliary lane can be applied to most traffic conditions and has a smaller land occupation than the traditional design, which is an optimization and improvement for the traditional design form.

TBM Rapid Tunneling Roadway Support Parameters Design and Process Research

Taking the specific production geological conditions of the auxiliary transportation lane in the west area of Gaojiabao coal mine of Shaanxi Zhengtong Coal Industry as the research background, based on the anchorage support theory and the characteristics of the TBM digging process, numerical simulation, theoretical analysis, and other research methods were used to investigate the depth of the destruction of the plastic zone of the surrounding rock of the roadway to form the reasonable support parameters of a large cross-section of hard rock roadway suitable for TBM digging and to propose an intelligent digging and support process of the TBM corresponding to the on-site practice. The proposed intelligent tunneling support technology corresponds to a field practice of TBM. The study shows that: combined with the field industrial test and adjusted by the peripheral rock deformation and damage law, the anchor diameter of 20 mm, the length of 2500 mm left-hand threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm, and the anchor diameter of Φ21.8 mm, the length of 6200 mm left-handed threaded steel anchors, row spacing of 1100 mm, spacing of 1200 mm are the most reasonable solutions, which can ensure the control of the tunnel peripheral rock. The program is the most economically efficient in ensuring the control of deformation of the roadway perimeter rock and maintaining normal use.

Operational Analysis to Establish Guidelines for Designing Auxiliary Lanes on Frontage Roads

Auxiliary lanes (ALs) provide significant operational benefits by spreading merging or weaving movements over a long distance or by providing an extra lane of capacity through a freeway bottleneck or signalized intersection. However, if ALs are not long enough, they may produce merge bottlenecks and queue spillbacks onto the main lanes of the freeway or arterial, creating operational and safety concerns. While there is literature or guidance for ALs on freeways, there is minimal design guidance for ALs on frontage roads. This study systematically examines various design elements of ALs on frontage roads and the design parameters that influence these design elements by leveraging microsimulation. The key purpose of this study is to develop recommendations for the length of ALs in six common frontage road design configurations based on the selected nine design parameters. More than 3,000 simulation runs were performed to develop and compare guidance with the existing design manuals. The results reveal new insights that would complement existing design guidance.

The Largest Space-Asymmetric-Curved-Single Tower Twisted-Cable-Plane Cable-Stayed Bridge—Tuojiang Bridge of Jinjianren Expressway Phase II

PDF HTML XML Export Cite reminder The Largest Space-Asymmetric-Curved-Single Tower Twisted-Cable-Plane Cable-Stayed Bridge—Tuojiang Bridge of Jinjianren Expressway Phase II DOI: 10.59238/j.pt.2023.01.008 Author: Affiliation: (Tongji Architectural Design (Group) Co., Ltd., Shanghai 200092, China) Clc Number: Fund Project: Article | Figures | Metrics | Reference | Related | Cited by | Materials | Comments Abstract:The Tuojiang Bridge of Jinjianren Expressway Phase II is located in Jianyang City and the Eastern New District of Chengdu, all the section length is 4.3 km with a total construction and installation cost of about 1.74 billion yuan. The road is classed as both a first-class highway and an urban expressway, with a design speed of 80 km/h for the main line and 40 km/h for the auxiliary lanes. Tongji University Architectural Design (Group) Co., LTD designed the main bridge which is an urban landscape bridge with a length of 963 m. The main bridge adopts 45+185+238+45m single-tower double-cable-plane cable-stayed span layout, and the approach bridge adopts prestressed small box girder structure. Reference Related Cited by

Hazard-based duration modelling of merging time interval on freeway on-ramps

Abstract Freeway on-ramps suffer high crash risks due to frequent merging behaviours. This study developed hazard-based duration models to investigate the merging time interval on freeway on-ramps based on microscopic trajectory data. Fixed effect, random effect and random parameters Weibull distributed accelerated failure time models were developed to capture merging time as a function of various dynamic variables. The random parameters model was found to outperform the two counterparts since the unobserved heterogeneity of individual drivers was captured. Modelling estimation results indicate that drivers along the merging section with an auxiliary lane perform a smooth merging process and are easily affected by speed variables. Dynamics of leading and following vehicles on the merging and target lanes are found to influence the merging time interval for merging without an auxiliary lane, whereas the influence of surrounding vehicles is marginal for those with an auxiliary lane. The findings of this study identify potential countermeasures for improving safety during the merging process.

Safety Analysis of Merging Vehicles Based on the Speed Difference between on-Ramp and Following Mainstream Vehicles Using NGSIM Data

Highway merging points are critical elements due to the interactions between merging vehicles and following vehicles on the outermost lane of the highway stream. Such interactions could have significant implications for safety and capacity at ramp locations. The aim of this study was to investigate the spacing adjustment behavior by the interacting drivers at merging locations. In this regard, we relied on the NGSIM trajectory dataset to investigate the impacts of the speed difference between the following and merging vehicles on a space headway, considering different geometric designs and vehicle classes. Nonlinear regression models were estimated to analyze the interactions. The results showed a significant and exponential tendency for headway reduction, particularly when the difference in speed was higher than 30 km/h. In addition, the findings revealed that the highway with an auxiliary lane performed better in terms of headway reduction. Furthermore, the space headway reduction trend was higher when the following vehicle was a truck rather than a car. Policymakers and practitioners aiming to improve road safety at merging locations could use this study’s findings. The resulting parameters can also be utilized in microsimulation models, e.g., for headway adjustment behavior in car-following models.

Learning to Predict 3D Lane Shape and Camera Pose from a Single Image via Geometry Constraints

Detecting 3D lanes from the camera is a rising problem for autonomous vehicles. In this task, the correct camera pose is the key to generating accurate lanes, which can transform an image from perspective-view to the top-view. With this transformation, we can get rid of the perspective effects so that 3D lanes would look similar and can accurately be fitted by low-order polynomials. However, mainstream 3D lane detectors rely on perfect camera poses provided by other sensors, which is expensive and encounters multi-sensor calibration issues. To overcome this problem, we propose to predict 3D lanes by estimating camera pose from a single image with a two-stage framework. The first stage aims at the camera pose task from perspective-view images. To improve pose estimation, we introduce an auxiliary 3D lane task and geometry constraints to benefit from multi-task learning, which enhances consistencies between 3D and 2D, as well as compatibility in the above two tasks. The second stage targets the 3D lane task. It uses previously estimated pose to generate top-view images containing distance-invariant lane appearances for predicting accurate 3D lanes. Experiments demonstrate that, without ground truth camera pose, our method outperforms the state-of-the-art perfect-camera-pose-based methods and has the fewest parameters and computations. Codes are available at https://github.com/liuruijin17/CLGo.

Modelling the driving speed on expressway ramps based on floating car data

Driving speed is one of the key concepts and risk factors in transportation research. The insights into operational and safety aspects of driving can be provided by floating car data (FCD), collecting information about speed, position and time by vehicles themselves. FCD are often recorded at high frequency, representing a continuous phenomenon. As such, convenient approach can be functional data analysis (FDA). Speed trajectories are investigated, identifying sections with rapid changes of speed and sections where drives in central and auxiliary lanes cannot be distinguished in terms of their speed. The effect of curvature and auxiliary lanes on driving speed was shown by functional regression models. Significant influence of road shape on speed was found for ramps with complex shape. The accuracy of regression models was assessed by RMSE, NRMSE, and precision of estimators by point-wise confidence intervals. The analysis was performed on an expressway interchange in Brno, Czech Republic.

Examination of an Effective Sign Arrangement in an Auxiliary Lane Section of Multilane Expressways

Examination of an Effective Sign Arrangement in an Auxiliary Lane Section of Multilane Expressways

Research on Truck Traffic Volume Conditions of Auxiliary Lanes on Two-Lane Highways

The larger the proportion of truck traffic volume, the greater the impact on traffic efficiency, and overtaking behavior will also have an impact. Therefore, in order to clarify the truck traffic volume of the freight two-lane highway due to the difficulty of overtaking, an actual vehicle test is carried out. This involves selecting the appropriate two-lane test section, recording each moment and speed in the driver’s overtaking behavior, performing multiple regression analysis to examine the relationship between the overtaking conflict time and design speed and traffic volume, determining a reasonable evaluation series of two-lane road overtaking risk and the corresponding overtaking conflict time threshold by the Fisher optimal segmentation method, and giving an overtaking behavior risk evaluation method based on conflict time. Finally, according to the overtaking conflict time model, different truck traffic conditions are obtained. The research results show that overtaking conflict time is negatively correlated with the traffic volume and design speed of the lane. Through the risk assessment of the corresponding overtaking behavior, the three levels of serious conflict, general conflict and non-conflict are determined, and the freight traffic volume corresponding to different conflict levels at different speeds is calculated, which provides a reference for setting auxiliary lanes for the two-lane freight highway.

Alternatives to enhance traffic conditions at U-turn sites

Traffic simulation models play a major role in allowing traffic engineers to assess complex traffic situations such as U-turn section. Such models help in proposing solutions and proposing alternative scenarios without committing too many expensive resources and this models are necessary to implement alternative strategies in the field. Simulation traffic models can significantly improve the quality of road network planning and design in urban areas. According to filed observation, the U-turn movement cause traffic congestion at both origin and distention (opposite) roads. This study introduces many alternatives to enhance the movement at U-turn section. These alternatives have been tested by using simulation models. The PTV VISSIM software is used to development the models. This development model has been calibrated and validated by using filed data collected from Al-Diwaniyah city, Iraq.
 References
 [1] Combinido, J.S.L. and Lim, M.T., "Modeling U-turn traffic flow", Physica A: Statistical Mechanics and its Applications, Vol. 389, No. 17, (2010), 3640-3647.
 [2] Della, R. H., Hanafiah, Arliansyah, J., & Artiansyah, R. (2015). Traffic Performance Analysis of U-turn and Fly Over U-turn Scenario; A Case Study at Soekarno Hatta Road, Palembang, Indonesia. Procedia Engineering, 125, 461–466. doi: 10.1016/j.proeng.2015.11.123
 [3] Al-Obaedi, J., "Investigation the effect of speed humps on merging time of u-turn traffic", Ain Shams Engineering Journal, Vol. 10, No. 1, (2019), 1-4.
 [4] Al-Obaedi, J., " Simulating the Effect of Speed Humps on the U-Turn Traffic", international Journal of Engineering, Vol. 32, (2019), Pages 1773-1780.
 [5] Meel I, Satirasetthavee D, Kanitpong K, Brannolte U. The Optimal Design of UTurns on Thai Highways. Acta Technica Jaurinensis 2014;7(1):21–32.
 [6] Meel I, Brannolte U, Satirasetthavee D, Kanitpong K. Safety impact of application of auxiliary lanes at downstream locations of Thai U-turns. IATSS Research 2017;41(1):1–11.
 [7] Meel, I., "The optimal design of u-turns on thai highways", Acta Technica Jaurinensis, Vol. 7, No. 1, (2014), 21-32.
 [8] Yang, X. (2001),” CORSIM-Based Simulation Approach to Evaluation of Direct Left Turn Versus Right Turn Plus U Turn from Driveways. (Ph.D dissertation), University of South Florida, Tampa.
 [9] Detemple, J., Garcia, R., & Rindisbacher, M. (2007). Chapter 21 Simulation Methods for Optimal Portfolios. Handbooks in Operations Research and Management Science, 867–923. doi:10.1016/s0927-0507(07)15021-0.
 [10] Vaitkus, Audrius, et al. "Traffic Calming Measures: An Evaluation of the Effect on Driving Speed." PROMET –Traffic &Transportation 29.3 (2017): 275-285.doi: 10.7307/ptt. v29i3.2265.
 [11] World Health Organization. Global status report on road safety 2015. World Health Organization, 2015
 [12] AL-Jameel H. A. E (2014). Contribution to the U-turn design at median opening in Iraq: Al-Najaf city as a case study, Kufa Journal of Engineering (K.J.E).
 [13] Della, R. H., Hanafiah, Arliansyah, J., & Artiansyah, R. (2015). Traffic Performance Analysis of u-turn and Fly Over u-turn Scenario; A Case Study at Soekarno Hatta Road, Palembang, Indonesia. Procedia Engineering, 125, 461–466. doi: 10.1016/j.proeng.2015.11.123 
 [14] Zainab A T Al-Kareawi and Jalal T S Al-Obaedi (2021). Simulation of U-turn traffic based on VISSIM and PARAMICS micro simulation, J. Phys.: Conf. Ser. 1895 012030 doi:10.1088/1742-6596/1895/1/012030.

Optimizing operations at freeway weaves with connected and automated vehicles

In this research, we propose novel mathematical models and algorithms for optimizing connected and automated vehicles’ (CAVs) trajectories at freeway weaving segments assuming 100 percent CAV market penetration. The proposed system receives vehicle arrival information and generates optimal trajectories that are relayed to the CAVs. The algorithm simulates vehicle arrivals and develops optimal vehicle trajectories on a 2-lane weaving section (one mainline and one auxiliary lane). We test the optimization algorithm under a variety of demand scenarios and using real-world arrival data. Results suggest that the proposed algorithm increases the average travel speed and capacity by 12 to 16% and up to 11%, respectively when compared to HCM estimates. Also, our case study shows the algorithm increases the average speed by 17%, 30%, and 38% for minimum time headways of 1.7 s, 1.4 s, and 1 s, respectively, compared to conventional vehicles.

Modeling of Merging Decision during Execution Period Based on Random Forest

This study aims to investigate the key feature variables and build an accurate decision model for merging behavior during the execution period by using a data-driven method called random forest (RF). To comprehensively explore the feature variables during merging execution period, nineteen candidate variables including speeds, relative speeds, gaps, time-to-collisions (TTCs), and locations are extracted from a dataset including 375 noise-filtered vehicle trajectories. After the variable selection process, an RF model with 9 key feature variables is finally built. Results show that the gap between the merging vehicle and its putative following vehicle and the ration of this gap to the total accepted gap are the two most important feature variables. It is because merging vehicle drivers can easily observe the putative leading vehicles and control the relative speeds and positions to the putative leading vehicles and they tend to leave more space for their putative following vehicles. Relative speed between the merging vehicle and its following vehicle in the auxiliary lane is the only variable related to the vehicles in the auxiliary lane, which means merging vehicles mainly focus on the traffic condition in the adjacent main lane. Evaluation of the performance in comparison with the state-of-the-art method reveals that the proposed method can obtain much more accurate results in both training and testing datasets, which means RF is practical for predicting the merging decision behavior during execution period and has better transferability.

Evaluating Designs of a Three-Lane Exit Ramp Based on the Entropy Method

The interchange diverging area is a bottleneck section of the freeway. If the capacity of a two-lane exit cannot meet the traffic demand, it will lead to a reduction in the overall operational efficiency of the freeway. To fundamentally improve the capacity of the diverging area, designers have considered expanding the two-lane exit to a three-lane exit. However, the existing Chinese design specifications do not include a design for a three-lane exit, and the method of increasing the number of ramp lanes by setting up auxiliary lanes according to traditional design concepts leads to the mainline widening section being too long, thus increasing the construction land use and project cost. Therefore, this paper proposes an innovative three-lane exit design based on a specific two-lane exit at an interchange in Xi’an. According to the different traffic organization methods, three microscopic simulation models of diverging areas were constructed by using VISSIM. The entropy method was used to objectively calculate the weights of the four selected evaluation indexes, and a comprehensive evaluation and applicability analysis of the current situation and the three-lane exit design schemes were conducted. The results show that the optimal combination of the schemes calculated by the entropy method increases the traffic volume by up to 40% and reduces delays by 50-88%.