Poor visual conditions in tunnels can easily cause traffic accidents, and it is difficult for emergency services to reach these areas. As an economical and effective visual guiding device, ...delineators have attracted wide attention. Based on the actual alignment of the Qinling Mountain No.1, No.2 and No.3 tunnels of the G5 Expressway in Xi'an City (Shaanxi Province, China), this paper designs a simulation experiment. Through a simulator study and a questionnaire survey, this paper discusses how delineators affect drivers' visual characteristics (including fixation area and pupil size) in different settings and with different road alignments. Twenty-five subjects participated in this research. The results show that setting delineators in tunnels can continuously guide drivers' vision and attract their attention to focus on the pavement. Compared with setting only pavement delineators, setting wall delineators and pavement delineators together can provide better guiding effects and ensure driving safety in both straight and curved sections. In addition, when driving in tunnels equipped with delineators, especially tunnels with both wall delineators and pavement delineators, the participants exhibited a smaller pupil diameter and lower pupil diameter change rate. In terms of the relationship between pupil size and road alignment, the results indicated that regardless of what type of delineator was used, the drivers exhibited the smallest pupil size and lowest pupil change rate when driving on the straight section compared with the curved sections.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
With the continuous construction of transportation infrastructure, intersection nodes have been increasing rapidly, bringing growing numbers of tunnel- and exit-adjacent sections (TEAS) in mountain ...expressways in China. With the complex variation in the surrounding environment, drivers always face congestion and confusion on tunnel and the exit connecting sections (TECS) without adequate length, meanwhile excessively long TECS create detours. To better provide a sustainable design strategy for TEAS, based on a certain section of expressway in Shaanxi, China, this paper establishes a theoretical calculation model through analysis. The characteristics of traffic flow and drivers' light adaptation at tunnel exit are obtained through data collection and driving tests, and the length requirements of the tunnel and exit connecting sections (TECS) are discussed. A VISSIM microscopic simulation model is also built under various design schemes and entropy-based multi-attribute decision making (EBMADM) is used to objectively calculate the weights of the four selected evaluation indexes. Then, the design schemes of the TECS with different lengths have been comprehensively evaluated. The results show the match between the evaluation results of EBMADM with theoretical calculations under existing traffic conditions, which proves the rationality of EBMADM in such problems. For more cases, the results of the EBMADM evaluation show a positive correlation between the length of TECS for the best performing design scheme with traffic volume and diverging ratio.
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Frequent consecutive lane changes and the barrier effect produced by trucks can always contribute to rapid access to the capacity bottleneck at expressway exits, thereby reducing operational ...performance. This paper proposes to retrofit the conventional interchange design to reduce lane changes and compares them with conventional design and passenger vehicle and truck separation (PVTS) design from multiple fields via VISSIM numerical simulation, which is developed and calibrated with traffic data collected on the eight-lane expressway in China at four levels of service (LOS). Comprehensive evaluation (CE) results reveal that the PVTS strategy improves operational performance by 10–20% at multilane expressway exits, while lane separation around interchanges also yields a similar gain. However, ramps on both the left and right sides show less effective improvement and are even negative at LOS-A and LOS-B. All PVTS and improved designs produce a better comprehensive improvement ratio with a LOS decrease, and improved designs achieve optimal performance below LOS-B with construction cost taken into consideration.
Given the rapid construction of freeways in developing countries such as China, land use is constantly under strict constraints, leading to challenges in adopting conventional layouts for ...interchanges. Implementing right-turn ramps on the left (RTRL) at interchanges can minimize land occupancy; however, the traffic safety level in this type of diversion area design requires extra attention. This study examines the decision sight distance for right-turn exit ramps on the left side. Utilizing unmanned aerial vehicle (UAV) video and the YOLOv3 target detection algorithm, the original trajectory data of vehicles in the diversion area is extracted. Employing Kalman filtering and Frenet coordinate system conversion reveals microscopic vehicle lane-change patterns, velocities, and time headways. Furthermore, the driving simulation experiment assesses driver behaviors in RTRL, with subjective, task performance, and physiological measure indicators. Ultimately, the range of the decision sight distance is defined, and establishing a calculation model involves determining relevant parameters based on measured data and simulation outcomes. The results indicate potential insufficiencies in the decision sight distance when standardized values are applied to RTRL.
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.
Owing to the challenges faced by two-lane entrance ramps in merging areas on expressways in handling the growing traffic volume, designers are considering implementing three-lane entrance ramps. This ...approach alleviates capacity bottlenecks and facilitates efficient, safe, and green operations. However, according to the traditional design strategy, the long auxiliary lanes will bring large land occupation and construction consumption, creating obstacles to the reconstruction. To address this issue, this study proposes two new strategies and discusses the applicability of each scheme. A VISSIM microsimulation model was developed and calibrated using the collected data, and five evaluation indicators assessing environmental protection, capacity, traffic efficiency, safety, and construction consumption were selected. This study also presents a comprehensive evaluation(CE) method that combines the CRITIC (Criteria Importance Through Intercriteria Correlation) method and TOPSIS(Technique for Order Preference by Similarity to an Ideal Solution), which considers the association between indicators and offers a more rational evaluation, aiming to recommend optimal designs for various traffic cases. The results indicate that two-lane ramps are still the preferred choice for lower traffic volumes and merging ratios, whereas three-lane ramps demonstrate excellent potential for application under heavy traffic conditions. The CE reveals substantial improvements in optimal designs, with capacity, delay, CO emissions, and conflicts showing maximum enhancements of approximately 20%, 45%, 5%, and 55%, respectively.
Due to the increasing demand for transportation, road renovation is inevitable, and the emergence of work zones has become the most common problem in traffic control. There are many research results ...on the impact of work zones on traffic operation, but most of them focus on various capacity theoretical models or traffic flow control strategies and are mostly concentrated in highway work areas and urban road subway construction work areas. The location of these work zones is often unable to be changed and is mostly considered reasonable. At present, there is still a gap in selecting and evaluating the location of the work zone. Therefore, this article studied a bidirectional six-lane intersection in Xi’an and investigated the situation of traffic flow distortion caused by the setting of work zones at the intersection. Two different positions and forms of work zones were designed for evaluation and analysis. Firstly, we used VISSIM (2022 student) to simulate the original and proposed work zone road-occupation schemes and analyzed six indicators. Finally, in order to determine the optimal work zone locations under different traffic situations, we applied the entropy weight method (EWM) to assign weights to multiple indicators, thereby achieving a comprehensive assessment of various schemes. The results showed that the highest improvement level among the six indicators was 50.2%, and different schemes adapted to different traffic situations. However, occupying two lanes of the median opposite the exit lane performed better under high traffic volume. Occupying the median and lanes on both sides of the median is suitable for low traffic volume. Occupying two lanes of the entrance lane and using the opposite lane as the left-turn entrance lane is suitable for situations with high traffic volume in the opposite lane.
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%.
As the number of vehicles continues to grow in China, the problem of urban traffic congestion gets more serious, particularly at intersections. As a new type of unconventional intersection, the ...displaced left-turn (DLT) intersection has been widely recognized to improve the efficiency of intersections with heavy left-turn traffic flows. Converting an existing intersection into an intersection with additional DLT lanes is a valuable solution. However, the studies on DLT intersections mainly focus on performance, applicability, and safety. The guidelines on the specific engineering design process mostly come from experience, and the study on the considering multifactor design method is still insufficient. Therefore, this paper proposed an evaluation and analysis model of the lengths of added DLT lanes based on the entropy evaluation method, in which VISSIM and Surrogate Safety Assessment Model (SSAM) software were adopted for simulation. A design process for the length of the added DLT lanes was proposed with this model. An urban intersection in Xi’an was taken as a case study, and the application of the model and the design process was studied in detail. After selecting four evaluation indicators, the model was applied to calculate and analyze the optimal length of the added DLT lanes under 45 different traffic volume combinations. The recommended lengths of different situations were within the range recommended in the guidebook published by Federal Highway Administration. The results of the case study proved that the model proposed in this paper was advanced, reasonable, and practical.
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CEKLJ, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Due to the rapid growth of traffic volume, some existing expressways are being transformed into two-way ten-lane configurations. The increased lane flexibility of two-way ten-lane expressways implies ...a more serious mixing of passenger and freight traffic, thus necessitating a focus on traffic organization, especially at bottleneck sections. This study, based on field-measured data and traffic simulation, investigates the traffic applicability of five expressway entrance forms: conventional interchange entrance ramp (CI), passenger vehicles and trucks separation (PVTS), lanes separation around interchange (LSI), both left-side and right-side entrance ramp (LRER) and the stacked composite cross-section expressway (CCE). Using a comprehensive evaluation method, it provides optimal design solutions for varying traffic volumes, truck ratios, and merging ratios. Comprehensive evaluation results indicate that for one-way total traffic volumes exceeding 9,000 veh/h and truck ratios above 25%, the PVTS form should be prioritized. The LSI scheme demonstrates significant advantages when the truck proportion is below 30% and the merging ratio is above 20%. Additionally, due to its relatively low construction cost, it can serve as a good substitute for the PVTS approach. The LRER plan is unsuitable for entrance sections due to poor traffic capacity, increased CO emissions, and foreseeable safety issues. The strengths and applicability of PVTS, LSI, and CCE can guide the choice of entrance forms for ten-lane expressways.
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