Two interrelated aspects of the synthesis problem for regulated intersections of urban highways are considered. First, the question of determination of all possible distributions of the allowed ...intersection crossing trajectories between phases of the traffic light cycle (in other words, traffic separation schemes) is being resolved. An algorithm for solving this problem is described and illustrated. As a result, all feasible traffic separation schemes are being found, with a limit on the number of conflict points of merging tracks if needed. Secondly, the question of choosing the duration of phases for a specific traffic separation scheme is considered depending on the intensity of the incoming flows and their distributions among the permitted directions of intersection crossing. Methods are proposed for taking into account the transport demand and security requirements and a compromise between them.
The work analyses the conflict points between road andrailway traffic as points of collision. The growing frequency ofboth transport modes meeting at the same level results in thegrowing danger at ...these points resulting in turn in traffic accidentsat collision points requiring therefore implementation ofprotection measures.Since misreading of traffic signs, unadjusted driving of roadvehicles, passage of road vehicles when the barrier is lowered,and inattention of motorists and pedestrians are the most frequentcauses of traffic accidents at railroad crossings, adequateand economically optimal solutions need to be found.By solving the above-mentioned problems, using the signaland safety as well as construction measures, the authors suggestsolutions which would increase traffic safety at railroad crossings.
The objective of the railway is to offer high level of transportservices, i.e. the quality which is competitive to other transportmodes, but which minimises its internal costs at the same time.In ...order to increase the capacity of transport services andreduce the costs, splitting of trains between different categoriesof transport on separate railway lines will be more and more appliedin the 21" centtuy. Unfortunately, even in the developedcountries there will be lines or line sections where mixed trafficwill be cmTied, and in developing countries this will often be thecase even on the main trunk lines.Therefore, a topical issue is to establish the capacity andchoose the right solution. The problem becomes more complexin cases when two double-track lines with mixed traffic need tobe connected and the restructuring of traffic implemented. Atthe same time the exits to two new double-track lines with thespecific train categories have to be ensured and the requiredquality of transport services maintained.In this paper, the impact the capacity has on quality is discussedand some basic characteristics of a model, which enablesthe research of the conflict points capacity, i.e. of convergingand diverging points of two double-track lines is given. Although,there are some analytical elements in this model, it isessentially simulation which enables us to carry out tests underdifferent conditions, to study different variants and to systematisedifferent indicators and make conclusions.
Accidents at intersections in Queensland accounted for 45% of total accidents and 19% of fatal accidents on the State roads in 2002. The number of accidents at intersections is purported to be ...primarily correlated to the number of conflict points but geometric characteristics also influence intersection safety. Queensland Transport database of reported accidents over the past ten years has been used in this study to investigate the contribution of intersection design and characteristics on the relative safety of intersections. Queensland Transport’s road crash database, WebCrash2, has been used to analyse the accident records at intersections in the Townsville region. The detailed analysis has included road user, vehicle type, collision type, BAC, use of seat belt and intersection type. Considering the common variations in the number of approaches, entry and exit lanes, type of control, phase design for signalisation, the road environment and other features like flaring, channelisation and signage, each intersection is peculiar and unique in some way. However, research has been focussed on three main types of intersections. These include T junctions, cross intersections and roundabouts. Three levels of control are also considered. The objective is to relate the intersection safety to the number of conflict points, conflict types, and intersection geometry. The results show that roundabouts are the safest types of intersection while uncontrolled cross intersections are least safe. The level of safety decreases with the increase in the number of approaches and the number of conflict points.
In order to set left-turn prohibition measures rationally, left-turn prohibition measures installation warrants at unsignalized intersection are discussed. While the analyses on conflict ...characteristics generation mechanism and different detour types of left-turn traffic are also described in this paper. We define conflict points as the sum of the two convergent traffic volume and establish intersection conflict points calculation model before and after taking left-turn prohibition measures. Then the conflict points variation value is taken as left-turn prohibition evaluation standard. If the variation value decreases after setting left-turn prohibition measures, we believe the measure is feasible; Otherwise, it is not suitable. Then an example is presented as verification which showing good results. The research will provide a basis for the implementation of left-turn prohibition measures at unsignalized intersections and improve its traffic efficiency.
•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∗.
•Conflict-free routing algorithms for automated vehicles in dedicated zones.•Conflict-point networks with time occupations on conflict points.•Dynamic platoon strategy to reduce delay in heavy ...traffic.•Deep reinforcement learning for optimizing the platoon sizes.
With the fast development of automated vehicle (AV) technologies, scholars have proposed various innovative local traffic control schemes for more effective management of AV traffic, especially at intersections. However, due to computational intractability, the investigation of network-level AV control is still at the initial stage. This study proposes a space-time routing framework applicable in dedicated AV zones. To relieve the computational load, we establish a node-based conflict point network to model realistic road networks, and at each conflict point, we record the space-time occupations of AVs in continuous timelines. Then, based on the conflict point network, we develop two space-time routing algorithms for each AV once it enters the dedicated AV zone to minimize its trip travel time while maintaining the non-collision insurances; these two algorithms can trade-off between solution quality and computational load. Furthermore, to enhance the network throughput for handling heavy traffic, we develop a ”platoon strategy” that forces AVs to pass through conflict points in platoons, and we adopt Deep Q-learning (DQN) to optimize the platoon sizes at different spots dynamically. Numerical tests show that both proposed algorithms perform well in that they can execute the routing tasks with very limited computational time, and the average vehicle delay approaches zero when the traffic is relatively mild. Meanwhile, compared with the FCFS policy and the optimization-based approach, the platoon strategy can greatly reduce the average vehicle delay under congested scenarios and give a better balance between the optimality and real-time performance.
•Safety performance of two proposed service interchange designs were reviewed.•The DDI and the new Milwaukee B were introduced as the safest interchange in terms of conflict frequency.•The new ...synchronized had the best performance from the viewpoint of severity of the conflicts.•Synchronized and DDI can be considered as the safe alternatives for failing diamond interchanges.
Interchanges have high crash rates and large impacts on traffic operations. The main objective of this research is to analyze the safety performance of two new interchanges, the synchronized interchange and the Milwaukee B interchange. The primary method of study was microscopic simulation modeling using the Surrogate Safety Assessment Model (SSAM) program to estimate the quantity and type of conflicting interactions in each interchange. A comprehensive series of simulation scenarios were considered to include different conditions of traffic volumes, traffic turning ratios, traffic distribution, and heavy vehicles percentages. Afterward, outcomes were analyzed with two-way Analyses of Variance (ANOVAs) to compare the mean values of conflicts. Based on the results, the diverging diamond interchange (DDI) and Milwaukee B were the safest designs regarding observed conflicting interactions in the simulation models; however, the DDI did not seem as reliable from the viewpoint of wrong way movements. The new synchronized interchange, the parclo B, and the Milwaukee A (an existing interchange in Milwaukee, WI) showed the same rate of conflicts. The synchronized interchange may be advantageous because it was estimated to reduce the severity of crashes due to fewer crossing conflicts, a lower speed of conflicts, and a higher time to collision. The conventional diamond was the most dangerous design based on our measures. The DDI and the synchronized interchange look like plausible substitutes for reconstructing an unsafe diamond interchange due to the similarities in their required space.
Insufficient network capacity and conflicts between pedestrians and vehicles at roadway intersections can be critical obstacles to the operational efficiency of evacuation activities. Reducing ...pedestrian - vehicle conflict points and expanding network capacities are two possible approaches to improving operational efficiency, especially when network accessibility varies in different evacuation stages. This paper integrates two types of network reconfiguration strategies, namely, the use of contraflow lane reversal for road lanes and pedestrian walkways and time-dependent conflict point elimination by separating pedestrian and vehicle flows with physical barriers at road intersections, to strategize pedestrian and vehicle moving directions during a mass evacuation. A multiobjective optimization model is formulated to adaptively select the appropriate locations for barriers according to different evacuation phases, and the model is solved by a modified genetic algorithm-based heuristic approach. An experiment on optimizing an urban regional evacuation network configuration in the case of a toxic gas leak accident was carried out to validate the proposed model. The numerical results show an increase of approximately 15% in the maximum evacuee throughput and a reduction of approximately 65% in the average exposure risk of evacuees of the optimal plans compared with the uncontrolled plan.
The rapidly growing popularity of electric scooters in recent years has allowed the road user to choose another alternative mode of transportation. On the one hand, it is an ecological means of ...transportation in the city, allowing you to quickly reach your destination; on the other hand, it is a vehicle that causes risk to road safety. Although this is a fairly new mode of transport, it is already of great concern for road safety authorities. E-scooter accidents are recorded with all road users – pedestrians, bicyclists, motor vehicles, other e-scooter riders, or even alone. In this article, the analysis made according to the accident data of 2019–2020 showed that the highest number of accidents occurred between e-scooters and vehicles. Most e-scooter accidents with motor vehicles occur in the intersection zone or during a vehicle turning manoeuvre to (or from) side streets and exit lanes. A descriptive statistical analysis showed that the proportions of the distribution of road accidents between accident participants changed significantly during the analysis period – the number of road accidents between e-scooters and bicycles increased, while the number of accidents between e-scooters and pedestrians decreased. The road accidents between e-scooters and other vulnerable road users are usually caused by sudden, unexpected manoeuvring of road users. Identification of accident schemes and locations is an additional tool for traffic organisation specialists and road safety professionals to prevent accidents, injuries, and fatalities.
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