Bi-Level Coordinated Merging of Connected and Automated Vehicles at Roundabouts

Traditional uncoordinated traffic flows in a roundabout can lead to severe traffic congestion, travel delay, and the increased fuel consumption of vehicles. An interesting way to mitigate this would be through cooperative control of connected and automated vehicles (CAVs). In this paper, we propose a novel solution, which is a roundabout control system (RCS), for CAVs to attain smooth and safe traffic flows. The RCS is essentially a bi-level framework, consisting of higher and lower levels of control, where in the higher level, vehicles in the entry lane approaching the roundabout will be made to form clusters based on traffic flow volume, and in the lower level, the vehicles’ optimal sequences and roundabout merging times are calculated by solving a combinatorial optimization problem using a receding horizon control (RHC) approach. The proposed RCS aims to minimize the total time taken for all approaching vehicles to enter the roundabout, whilst minimally affecting the movement of circulating vehicles. Our developed strategy ensures fast optimization, and can be implemented in real-time. Using microscopic simulations, we demonstrate the effectiveness of the RCS, and compare it to the current traditional roundabout system (TRS) for various traffic flow scenarios. From the results, we can conclude that the proposed RCS produces significant improvement in traffic flow performance, in particular for the average velocity, average fuel consumption, and average travel time in the roundabout.

Evaluation of Road Safety for Roundabout and Signalized Intersection

Traditional intersections have always caused accidents. There are numerous geometric intersection designs that best fit each situation. This study performed an operational and safety comparison with different intersection like signalized, unsignalized and roundabout to decrease the overall travel delay & collision at intersection and increase the safety using case study. This dissertation describes the application of the traffic conflict technique to estimate, traffic safety at intersections. Using data collected from surveys, traffic frequency and severity standards for signalized and roundabout have been established. The methodologies are developed incorporating the relative importance of different severity of different safety indices at intersection. The relative importance (weights) of very low, low, medium and high severity condition is developed using data collection and expert opinions experience people which have knowledge in development/safety development at intersection were obtained by conducting a survey. A questionnaire was prepared to obtain the relative importance of different severity of different parameter performance. The weights are developed in such a way that their values lie between 0 and 1. In proposed work design safety parameter for intersection for enhancement of safety at intersections and all safety design is implemented on MATLAB and analysis of the geometrical design for vehicle system in the intersection by MATLAB, analyses, the status of confliction and desired value obtained by comparison of actual value with available geometric designs and to enhance the safety at intersection and explores methods to solve the problem of collision at intersections. In this paper evaluate safety parameter of roundabout.

Receding Horizon Cooperative Platoon Trajectory Planning on Corridors with Dynamic Traffic Signal

In this paper, a trajectory control approach using model predictive control is proposed for cooperative (automated) vehicles. This control approach optimizes accelerations of the controlled connected and automated vehicle (CAV) platoon along a corridor with signalized intersections. The objectives of the proposed approach are to maximize the throughput first and optimize comfort, travel delay, and fuel consumption simultaneously after that. The throughput is determined according to the maximal number of CAVs that can pass the intersection during the green phase. Safety is included by penalizing smaller gaps between CAVs in the running cost. The red phase is taken into account as a virtual vehicle at the stop-line during the red time, thus the safe gap penalty with the virtual vehicle causes the first-stopping vehicle to decelerate or even stop facing the red phase. The acceleration and speed are constrained within the upper and lower bounds. The proposed approach is flexible in dealing with platoon merging, splitting, stopping, and queue-discharging characteristics at signalized intersections. Finally, the proposed control approach is verified by simulation under a baseline scenario and four scenarios, which consider signal settings and the anticipation of the red phase. The simulation results demonstrate the benefits of the proposed control approach on fuel savings, compared with the state-of-art approach which used the virtual vehicle term without anticipation. The adjustments of signal parameters in Scenario 3 and Scenario 4 demonstrate the applicability of the control approach under actuated signal control.

TRAVEL DELAY OF VEHICLES QUEUE AT A TRAFFIC SIGNAL

Mathematical modeling assumes that the vehicle’s volume has a uniform pattern. Due to traffic lightssettings, the number of vehicles queue grows linearly. The reality, the stochastic arrivals of the vehiclescould be (1) in the randomized arrivals, (2) in the form of groups/ platoon, or (3) in the mixed arrivals. Itis observed that the arrival of the vehicles in the queue tends to have a normal pattern. The objective ofthis research is to study the implications of the arrival categories to the travel delay. For simulation, ituses the numerical method referring to the real state. The result indicates that the calculations of thetravel delay become precise for all vehicles.

Performance Evaluation of Chinese High-Speed Railway Bridges Under Seismic Loads

The multi-span simply supported (MSSS) box girder bridge is the most used structural form for the high-speed railway (HSR) in China. In structural design, it is required that the MSSS bridge system has high stiffness and low deflection under the operation loads. With the expansion of the HSR network to regions that are seismically active, the seismic performance of MSSS bridges in these regions is an issue of great concern. In this study, the performance-based earthquake engineering (PBEE) methodology originally developed to quantify the seismic performance of buildings and bridges has been adopted to quantify the seismic performance of the HSR MSSS bridges in China. Typically, a four-span MSSS bridge used in China’s Sichuan–Yunnan HSR lines has been extensively assessed by the PBEE approach. This study is the first of its kind to systematically identify and quantify the damage states, repair actions, repair costs and travel delay losses for China’s HSR MSSS bridge system. The results reveal that the financial loss from the MSSS bridge system is highly dependent on the anchorage capacity of the fixed bearings. Overall, the costs of travel delay outweigh those for structural repair. Most of the financial loss can be attributed to the functional loss of the track-slab components and bearings of the HSR MSSS bridge system.

Influence of Night Rainfall on Stopping Sight Distance on Dark Roadways

Aim: To investigate the influence of night rainfall on stopping sight distance on dark roadways. Background: This study fills the research gap in stopping sight distance by looking at night rainfall impact on stopping sight distance on dark roadways. Objectives: To determine stopping sight distance under night rainfall (light, moderate and heavy) on dark roadways and compare the results with stopping sight distance under dry night on dark roadways. Methods: In a ‘with and without’ night rainfall impact studies, traffic volume, speed, vehicle type and rainfall data were collected at selected sites. All surveyed sites had rain gauge within the catchment area of about 1km. Rainfall intensity was divided into three groups (light, moderate, and heavy). Dry weather data were used as a control parameter. Results: Results show that the average SSD decrease attributed to light rainfall is 15.2m (14%), moderate rainfall 18.3m (16.8%), and heavy rainfall 21.2m (19.2%). Conclusion: Based on the results and findings, it is correct to conclude that the effect of night rainfall on dark roadways stopping sight distance is somewhat aberrant. It is also correct to suggest that night rainfall on dark roadways will cause a decrease in perception distance travel delay, an increase in braking distance and stopping sight distance.

Platooning of Autonomous Public Transport Vehicles: The Influence of Ride Comfort on Travel Delay

The development of advanced technologies has led to the emergence of autonomous vehicles. Herein, autonomous public transport (APT) systems equipped with prioritization measures are being designed to operate at ever faster speeds compared to conventional buses. Innovative APT systems are configured to accommodate prevailing passenger demand for peak as well as non-peak periods, by electronic coupling and decoupling of platooned units along travel corridors, such as the dynamic autonomous road transit (DART) system being researched in Singapore. However, there is always the trade-off between high vehicle speed versus passenger ride comfort, especially lateral ride comfort. This study analyses a new APT system within the urban context and evaluates its performance using microscopic traffic simulation. The platooning protocol of autonomous vehicles was first developed for simulating the coupling/decoupling process. Platooning performance was then simulated on VISSIM platform for various scenarios to compare the performance of DART platooning under several ride comfort levels: three bus comfort and two railway criteria. The study revealed that it is feasible to operate the DART system following the bus standing comfort criterion (ay = 1.5 m/s2) without any significant impact on system travel time. For the DART system operating to maintain a ride comfort of the high-speed train (HST) and light rail transit (LRT), the delay can constitute up to ≈ 10% and ≈ 5% of travel time, respectively. This investigation is crucial for the system delay management towards precisely designed service frequency and improved passenger ride comfort.

Optimizing Strategies for the Urban Work Zone with Time Window Constraints

Work zones that move with road maintenance tasks are enclosing and have caused severe traffic jams and the significant decline of road capacity. This paper proposes an intelligent-based multi-objects road maintenance optimization strategy based on a practical origin–destination (OD) matrix and complicated work schedules over a real urban road network. It focuses on the optimization of multi short-term maintenance tasks and the minimization of average travel delay for vehicles passing through. By taking the driving characteristic into account, static and dynamic variable speed limit strategies provide access to ensure safety on the working road network. Through this view, the problem was formulated as a mixed multi-object nonlinear program (MNLP) model with respect to the time window of the related sub-maintenance task. By using actual OD distribution matrix data, a series of microscopic simulated cases were conducted to test the model’s validity. Moreover, sensitive analyses of types of parameters (e.g., traffic safety threshold, traffic flow and working efficiency) with an optimal solution were discussed considering five different scenarios.

Optimal Platoon Trajectory Planning Approach at Arterials

Cooperative (automated) vehicles have the potential to enhance traffic efficiency and fuel economy on urban roads, especially at signalized intersections. An optimal control approach to optimize the trajectories of cooperative vehicles at fixed-timing signalized intersections along an arterial is presented. The proposed approach aims to optimize throughput first, and then to maximize comfort while minimizing travel delay and fuel consumption. The proposed approach is flexible in dealing with both quadratic and more complex cost functions. Assuming fixed timing signal control in a cycle and vehicle-to-infrastructure communication, the red phase is taken into account in position constraints for vehicles that cannot pass the intersection in the green phase. Safety is guaranteed by constraining the inter-vehicle distance larger than some desired value. The approach is scalable and can be used for joint trajectory planning of one platoon approaching another stationary platoon. It can also be extended to multiple intersections with fixed signal plans. To verify the performances of the controlled platoon, simulation under three different traffic scenarios is conducted, namely: an isolated intersection with/without downstream vehicle queues, and platoon control at multiple intersections. Three baseline scenarios without control are also designed to compare performances in relation to both mobility and fuel consumption in each controlled scenario. The results demonstrate that the controlled vehicles generate plausible behavior under control objectives and constraints. Moreover, the consideration of downstream vehicle queues and the application at both an isolated signalized intersection and arterial corridors on urban roads verify the flexible characteristics of the control framework.