On-ramp Junctions Research Articles

Game Theoretic Merging Behavior Control for Autonomous Vehicle at Highway On-Ramp

In the most of previous studies, social interactions between vehicles are not considered explicitly when designing decision making and motion planning module. Nevertheless, the strong interaction exists in the most of driving scenarios, especially in highway junction. This paper presents a game theoretic merging behavior control system for autonomous vehicle at on-ramp junction considering the interaction between the merging vehicle and following vehicle in the main lane. In this work, a driving style estimation is proposed to deal with the heterogeneity of driving style. Then we adopt a model predictive control (MPC) method to plan the optimal merging trajectory based on the game theoretic decision making result. Finally, simulation and Human-in-the-loop (HIL) experiment result shows the effectiveness of our approach in on-ramp merging scenario.

How Connected and Automated Vehicle–Exclusive Lanes Affect On-Ramp Junctions

Connected and automated vehicle (CAV) exclusive lanes are an important application of intelligent transportation technologies on highways. However, current research on CAV exclusive lanes mainly focuses on basic road segments rather than on on-ramp junctions. This paper analyzed the impact of CAV exclusive lanes on the traffic capacity of on-ramp junctions through theoretical analysis and numerical simulation. This paper established a capacity model for heterogeneous traffic consisting of CAVs and manual vehicles (MVs) considering the CAV degradation mechanism. Three key parameters, namely the CAV penetration rate, the proportion of CAVs on regular lanes, and a CAV platoon coefficient, were introduced into the heterogeneous traffic capacity model. Based on this input, the relationship between traffic capacity and the three parameters was analyzed on regular lanes. The critical CAV penetration rate at which a CAV exclusive lane reaches saturation was expressed mathematically. An on-ramp junction scenario with a CAV exclusive lane was simulated numerically with microscopic heterogeneous traffic flow models. Experimental results showed that congestion at the junction area no longer spread upstream after the CAV penetration rate exceeded 70% without CAV exclusive lanes. However, for the case in which a CAV exclusive lane was used, CAVs on the exclusive lane traveled quickly through the junction and effectively relieved traffic congestion when the CAV penetration rate reached 40%. The results also showed that a long acceleration lane slightly reduced the CAV platoon coefficient. In addition, a CAV exclusive lane improved traffic capacity when the CAV penetration rate was higher than 30%, regardless of the length of the acceleration lane.

Capacity drop and traffic control for a second order traffic model

In this paper, we illustrate how second order traffic flow models, in our case the Aw-Rascle equations, can be used to reproduce empirical observations such as the capacity drop at merges and solve related optimal control problems. To this aim, we propose a model for on-ramp junctions and derive suitable coupling conditions. These are associated to the first order Godunov scheme to numerically study the well-known capacity drop effect, where the outflow of the system is significantly below the expected maximum. Control issues such as speed and ramp meter control are also addressed in a first-discretize-then-optimize framework.

A Study on Lane Operation Restriction (LOR) Policy at On-ramp Junctions

On-ramp junctions on freeways are subject to vehicle merging interactions between main travel lanes and ramp flows. The turbulence created by these interactions often causes congestion, and can lead to breakdown when the combined volume from the ramp and the mainline exceed the capacity of the downstream freeway segment. This study discusses a potential application for freeway control policy at the ramp junction – the Lane Operation Restriction (LOR) policy.This policy would provide particular attention to traffic operation improvements at on-ramp junctions with relatively high flow rates from the ramp. Principles of LOR policy would be based on empirical data and analysis findings. The empirical data are analyzed upstream and downstream of on-ramp junctions on six-lane freeways using a database for the National Cooperative Highway Research Program (NCHRP) 3-37. It was observed that lanes 2 (middle lane) and 3 (median side lane) show a higher density-speed relationship than the shoulder lane upstream of the junctions. In addition, the breakdown condition and congestion spread across all freeway travel lanes when the flow of lane 1 (shoulder side lane) is suddenly increased to near capacity at the ramp influence areas. A simulation analysis employing the LOR policy is introduced evaluating the ramp junction influence areas, its downstream and upstream areas. It concludes that traffic operations in the vicinity of on-ramp junctions can be significantly improved when upstream vehicles are guided to shift from lane 1 to lanes 2 and 3 before arriving at on-ramp junctions and restraint lane changes at the ramp influence area.

Safety Impacts of Auxiliary Lanes at Isolated Freeway On-Ramp Junctions

This article presents a two-part study to quantify the safety impacts of auxiliary lanes at isolated on-ramp junctions on freeways. In the first part of this study, the safety performance of on-ramp junctions with auxiliary lanes was compared with isolated on-ramp junctions without an auxiliary lane. Sixteen sites with auxiliary lanes and 19 sites without an auxiliary lane were selected in Texas. Two thousand and twenty-six crash records from 2003 to 2008 were analyzed in terms of total crash rate, crash severity, and major crash types. The results show that isolated freeway on-ramp junctions with auxiliary lanes have a significantly lower average total crash rate and average rear-end crash rate. In the second part of this study, regression models were developed to relate crash rate with influencing factors for on-ramp junctions with auxiliary lanes. The best regression model shows that the crash frequency is positively proportional to the number of lanes on the freeway and the average daily traffic per lane on the freeway, but negatively proportional to the length of the auxiliary lane and the percentage of heavy vehicles on the freeway.

The optimization of On-ramp Junction Capacity based on Zippered Control Strategy

Traffic congestion on on-ramp metered areas will increase the delay and reduce the capacity of urban elevated road dramatically. The method of alternate driving has the function of increasing the capacity of the on-ramp metered areas under the crowded conditions effectively. Focusing on the variation of metered proportion of the main-road and on-ramp road, a cellular automaton based model was proposed with respect to the optimal capacity, which is judged by the interflow numbers. The proposed capacity model is expected to be an improvement to the traditional model with the theory of cellular automation. The evaluation work was carried out by the VISSIM software, and the simulations show good corresponding results according to the optimal capacity model.

Operation reliability for on-ramp junction of urban freeway

A disorder situation of traffic operation always appears in on-ramp junction area of urban freeway, because the operation action for vehicles presents the weaving condition, especially for different vehicle types. Based on the analysis on the cellular automata theory, and combining with on-site survey data, several key parameters were defined, namely, cellular length, cellular speed, cellular acceleration, updating time interval. In addition, cellular acceleration rule, cellular deceleration rule, random rule, lane-changing rule and other micro-simulation rules were set, and cellular automaton micro-simulation model was set up. Further-more, a micro-simulation module was developed for traffic operation actions of on-ramp junction with Matlab toolbox. Finally, a simulation experiment for traffic operation reliability was done with this micro-simulation module, and the situation of change for on-ramp junction area was obtained under the conditions of different mainline design speed, acceleration lane length, vehicle generation probability and lane-changing probability. The results show that operation reliability for on-ramp junction is determined by the parameters of the probability of vehicle generation and the length of acceleration lane, especially for on-ramp.

Gap Acceptance Capacity Model for On-Ramp Junction of Urban Freeway

The commonly-used capacity calculation approaches for ramp junctions are mostly based on the American Highway Capacity Manual method. It had been approved that the headways for vehicles following the Weibull distribution function at on-ramp junctions in urban freeway system. The paper examined the critical headway and following time by the modified drew method and the survey traffic flow data on-site. The gap-acceptance capacity calculating model was developed for on-ramp junctions of urban freeway, and the numerical integration method was used to solve the model. Finally, the capacity values were obtained in condition of different mainline design speeds and different acceleration lane lengths. The results indicated that the capacity value would grow with the increase of the acceleration length and mainline design speed, and the capacity values for on-ramp junctions would approach basic freeway segments capacity values while the acceleration lengths beyond 400 meters.