This study evaluated psychometric properties of the Intersection Point Height, derived from ground-on-feet force characteristics, as a tool for assessing balance control. We compare this metric with ...traditional center of pressure (CP) measurements.
Data from a public dataset of 146 participants, divided into younger (<60 years old) and older (≥60 years old) adults, were analyzed. Clinical tests included the Short Falls Efficacy Scale-International, International Physical Activity Questionnaire-Short Form, Trail Making Tests A and B, and the Mini-Balance Evaluation Systems Test. Reliability and validity were assessed through the intra-class correlation coefficient (ICC3,1) for mean Intersection Point Height in each test condition and Spearman's rho between summative Intersection Point Height (the sum of intra-condition mean values across all test conditions within one subject) and other variables of interest, respectively.
Mean Intersection Point Height showed good to excellent reliability (ICC = 0.712–0.901), similar to that of CP velocity (ICC = 0.733–0.922) and greater than that of variance CPx (0.475–0.768). Summative Intersection Point Height exhibited strong convergent validity with Trail Making Tests A and B (rho = 0.49, p < 0.001) and the Mini-Balance Evaluation Systems Test (rho = −0.47, p < 0.001). At most, a weak to moderate association (rho = 0.39–0.49, p < 0.001) was found between intra-condition mean Intersection Point Height with CP metrics. Intra-condition mean Intersection Point Height demonstrated weak to moderate convergent validity with several clinical measures (rho = 0.32–0.52, p < 0.001). In contrast, at most, a weak to moderate association (rho = 0.39–0.49, p < 0.001) was found between intra-condition mean Intersection Point Height with CP metrics.
The Intersection Point Height is a reliable and valid balance measure. Further, we believe that it is a more comprehensive evaluation than CP metrics.
•Valid and reliable, the zIP metric provides a robust measure for evaluating balance.•The reliability and validity of zIP are comparable to or surpass center of pressure (CP) metrics.•zIP has the potential to provide a more comprehensive balance assessment than CP metrics.
Connected and autonomous vehicles (CAVs), unlike conventional cars, will utilise the whole space of intersections and cross in a lane-free order. This article formulates such a lane-free crossing of ...intersections as a multi-objective optimal control problem (OCP) that minimises the overall crossing time, as well as the energy consumption due to the acceleration of CAVs. The constraints that avoid collision of vehicles with each other and with road boundaries are smoothed by applying the dual problem theory of convex optimisation. The developed algorithm is capable of finding the lower boundary of the crossing time of a junction which can be used as a benchmark for comparing other intersection crossing algorithms. Simulation results show that the lane-free crossing time is better by an average of 40% as compared to the state-of-the-art reservation-based method, whilst consuming the same amount of energy. Furthermore, it is shown that the lane-free crossing time through intersections is fixed to a constant value regardless of the number of CAVs.
•This paper used a propensity scores-potential outcomes framework, with genetic matching, to estimate the safety effects of the continuous green T (CGT) intersection relative to a conventional ...signalized T intersection.•Crash modification factors (CMFs) for the CGT were developed for total, fatal and injury, and target (rear-end, angle, and sideswipe) crashes.•The results show that the CMFs for all crash types were less than 1.0, indicating that the CGT intersection offers safety benefits relative to the traditional signalized T intersection.
The continuous green T intersection is characterized by a channelized left-turn movement from the minor street approach onto the major street, along with a continuous through movement on the major street. The continuous flow through movement is not controlled by the three-phase traffic signal that is used to separate all other movements at the intersection. Rather, the continuous through movement typically has a green through arrow indicator to inform drivers that they do not have to stop. Past research has consistently shown that there are operational and environmental benefits to implementing this intersection form at three-leg locations, when compared to a conventional signalized intersection. These benefits include reduced delay, fuel consumption, and emissions. The safety effects of the conventional green T intersection are less clear. Past research has been limited to small sample sizes, or utilized only statistical comparisons reported crashes to evaluate the safety performance relative to similar intersection types. The present study overcomes past safety research evaluations by using a propensity scores-potential outcomes framework, with genetic matching, to compare the safety performance of the continuous green T to conventional signalized intersections, using treatment and comparison site data from Florida and South Carolina. The results show that the expected total, fatal and injury, and target crash (rear-end, angle, and sideswipe) frequencies are lower at the continuous green T intersection relative to the conventional signalized intersection (CMFs of 0.958 95% CI=0.772–1.189, 0.846 95% CI=0.651–1.099, and 0.920 95% CI=0.714–1.185, respectively).
Abstract
Based on microsimulation, this study analyses the performance and behavior of motorized vehicles at the signalized intersection between the railway line and Ahmad Yani road-Jemursari road. ...For the survey of the volume of motorized vehicles, this intersection is divided into four intersections with eight directions of traffic movement and one direction of combined traffic movement. Microsimulation was carried out using Vissim software with nine parameters calibrated according to actual conditions during the peak hour observation period. The maximum queue length and motor vehicle delays for the peak hour observation period occur at intersections one in the north and two in the east. Performance of the intersection of Jl. Ahmad Yani-Jl. Jemursari is included in category F. The indicator F are traffic jams, low vehicle speeds, long queues, and vehicle delays. The following study of this paper is to make a geometric model of the intersection into a Fly Over model.
Under the Connected Vehicles (CV) environment, it is possible to create a Cooperative Vehicle Intersection Control (CVIC) system that enables cooperation between vehicles and infrastructure for ...effective intersection operations and management when all vehicles are fully automated. Assuming such a CVIC environment, this paper proposed a CVIC algorithm that does not require a traffic signal. The CVIC algorithm was designed to manipulate individual vehicles' maneuvers so that vehicles can safely cross the intersection without colliding with other vehicles. By eliminating the potential overlaps of vehicular trajectories coming from all conflicting approaches at the intersection, the CVIC algorithm seeks a safe maneuver for every vehicle approaching the intersection and manipulates each of them. An additional algorithm was designed to deal with the system failure cases resulting from inevitable trajectory overlaps at the intersection and infeasible solutions. A simulation-based case study implemented on a hypothetical four-way single-lane approach intersection under varying congestion conditions showed that the CVIC algorithm significantly improved intersection performance compared with conventional actuated intersection control: 99% and 33% of stop delay and total travel time reductions, respectively, were achieved. In addition, the CVIC algorithm significantly improved air quality and energy savings: 44% reductions of CO 2 and 44% savings of fuel consumption.
•3D CAV trajectories are formulated in the combined temporal-spatial dimensions.•A DFROC algorithm is developed to minimize average control delays at intersections.•Simulation models are developed to ...examine the proposed algorithm.•The proposed DFROC algorithm is superior to the existing control algorithms.
Traffic congestion has become a serious issue worldwide due to the rapid increase in population and traffic demands. Advances in connected automated vehicle (CAV) technology demonstrate the potential to improve traffic mobility and safety performance at intersections. An advanced intersection control system is proposed in this study to coordinate vehicle trajectories and ensure safety and operation efficiency at intersections. A temporal-spatial dimension extension-based trajectory coordination model is developed by formulating all possible trajectories of vehicles at the intersection. Correspondingly, according to the trajectory coordination model, two signal-free control algorithms, including the priority-based algorithm and the Discrete Forward-Rolling Optimal Control (DFROC) algorithm are proposed in this study to manage vehicles at the intersection. These two algorithms, together with the FCFS policy, are compared with the conventional signal control method in a SUMO-based simulation platform. Experimental results indicate that the proposed algorithms outperform the signal control method in terms of reducing total traffic delays at intersections and increasing intersection capacity and operation efficiency.
•Development of a signal-head-free intersection control logic for connected and autonomous vehicles.•Dynamic optimization of acceleration rates to maximize intersection throughput with safe ...trajectories.•Development of a dynamic programming technique incorporating Monte Carlo tree search algorithm.•Travel time reductions of 59.4%–83.7% compared to fixed-time and fully-actuated control case studies.•Potential to eliminate the number of near-crash instances to zero in case studies.
Establishment of effective cooperation between vehicles and transportation infrastructure improves travel reliability in urban transportation networks. Lack of collaboration, however, exacerbates congestion due mainly to frequent stops at signalized intersections. It is beneficial to develop a control logic that collects basic safety message from approaching connected and autonomous vehicles and guarantees efficient intersection operations with safe and incident free vehicle maneuvers. In this paper, a signal-head-free intersection control logic is formulated into a dynamic programming model that aims to maximize the intersection throughput. A stochastic look-ahead technique is proposed based on Monte Carlo tree search algorithm to determine the near-optimal actions (i.e., acceleration rates) over time to prevent movement conflicts. Our numerical results confirm that the proposed technique can solve the problem efficiently and addresses the consequences of existing traffic signals. The proposed approach, while completely avoids incidents at intersections, significantly reduces travel time (ranging between 59.4% and 83.7% when compared to fixed-time and fully-actuated control strategies) at intersections under various demand patterns.
•New protocol for reservation-based intersection control that admits optimized trajectories.•Mixed integer linear programming formulation using conflict-point vehicle separation.•Rolling horizon ...solution approach that can be solved efficiently for large time periods.•Improves significantly over the widely-used first-come-first-served policy.
Reservation-based intersection controls, in which vehicles reserve space-time paths through the intersection, have the potential to make greater use of intersection capacity than traffic signals. However, the efficiency of previous microsimulations of reservations has been severely limited by a protocol that requires vehicles to request reservations and the intersection manager to accept or reject them. We propose a new protocol, AIM∗, in which the intersection manager assigns reservations to vehicles, to greatly increase the optimization possibilities. Then, we present a mixed integer linear program for optimally choosing vehicle reservations under AIM∗. The formulation is similar to conflict resolution models for aviation, and ensures separation at all points that vehicles might intersect. We therefore present a rolling-horizon algorithm to extend the method to larger numbers of vehicles. Results show that the optimal reservation assignments from AIM∗ significantly reduce delays over previous protocols. Furthermore, the rolling horizon solutions have similar delays to a fixed horizon, thereby providing an efficient method of implementing AIM∗.
•This paper proposes a network-wide method to identify intersection traffic congestion in a road network.•The proposed method is solely based on low-frequency probe vehicle data, i.e., ...map-independent.•It is able to rapidly and approximately detect intersection congestion along all turning directions.•It is a computer-aided method in the era of big data can greatly decrease traffic engineers’ workload.
Locating the bottlenecks in cities where traffic congestion usually occurs is essential prior to solving congestion problems. Therefore, this paper proposes a low-frequency probe vehicle data (PVD)-based method to identify turn-level intersection traffic congestion in an urban road network. This method initially divides an urban area into meter-scale square cells and maps PVD into those cells and then identifies the cells that correspond to road intersections by taking advantage of the fixed-location stop-and-go characteristics of traffic passing through intersections. With those rasterized road intersections, the proposed method recognizes probe vehicles’ turning directions and provides preliminary analysis of traffic conditions at all turning directions. The proposed method is map-independent (i.e., no digital map is needed) and computationally efficient and is able to rapidly screen most of the intersections for turn-level congestion in a road network. Thereby, this method is expected to greatly decrease traffic engineers’ workloads by providing information regarding where and when to investigate and solve traffic congestion problems.
•An effective traffic organization method is proposed for CAVs in road networks.•An effective iterative adjustment strategy is used to optimize trajectories.•A novel composite road planning strategy ...is designed for different demands.•The proposed method ensures safe, efficient, energy-saving, and comfortable trips.
Connected automated vehicles (CAVs) have been currently considered as promising solutions for realization of envisioned autonomous traffic management systems in the future. CAVs can achieve high desired traffic efficiency and provide safe, energy-saving, and comfortable ride experience for passengers. However, in order to practically implement such autonomous systems based on CAVs, there exist several significant challenges to be dealt with, such as coupled spatiotemporal constraints on CAVs’ trajectories at unsignalized intersections, multiple objectives for trajectory optimization in road segments, and heterogeneous decision-making behaviors of CAVs in road networks with highly dynamic traffic demand. In this paper, we propose a cooperative autonomous traffic organization method for CAVs in multi-intersection road networks. The methodological framework consists of threefold components: an autonomous crossing strategy based on a conflict resolution approach at unsignalized intersections, multi-objective trajectory optimization in road segments, and a composite strategy for route planning considering heterogeneous decision-making behaviors of CAVs based on social and individual benefit, respectively. Specifically, we first identify a set of potential conflict points of different CAVs’ spatial trajectories at the intersection, and then design different minimum safe time headways to resolve conflicts. Under the constraints of entry and exit conditions at adjacent intersections, we propose a multi-objective optimal control model by jointly considering vehicle safety, energy conservation, and ride comfort, and then analytically derive a closed-form solution for optimizing the CAVs’ trajectories. Furthermore, with the purpose to adapt dynamic traffic demand, we propose a composite strategy for route planning by coordinating heterogeneous decision-making behaviors of CAVs in road networks. Finally, extensive simulation experiments have been performed to validate our proposed method and to demonstrate its advantage over conventional baseline schemes in terms of global traffic efficiency. Additional numerical results are also provided to shed light on the impact of the proportion of CAVs with heterogeneous decision-making behaviors on the global system performance.
