The combined bottleneck effect is investigated by modeling traffic systems with an on-ramp and a nearby bus stop in a two-lane cellular automaton model.Two cases,i.e.the bus stop locates in the downstream section of the on-ramp and the bus stop locates in the upstream section of the on-ramp,are considered separately.The upstream flux and downstream flux of the main road,as well as the on-ramp flux are analysed in detail,with respect to the entering probabilities and the distance between the on-ramp and the bus stop.It is found that the combination of the two bottlenecks causes the capacity to drop off,because the vehicles entering the main road from the on-ramp would interweave with the stopping (pulling-out) buses in the downstream (upstream) case.The traffic conflict in the former case is much heavier than that in the latter,causing the downstream main road to be utilized inefficiently.This suggests that the bus stop should be set in the upstream section of the on-ramp to enhance the capacity.The fluxes both on the main road and on the on-ramp vary with the distance between the two bottlenecks in both cases.However,the effects of distance disappear gradually at large distances.These findings might give some guidance to traffic optimization and management.
This paper uses the cellular automaton model to study the dynamics of traffic flow around an on-ramp with an acceleration lane.It adopts a parameter,which can reflect different lane-changing behaviour,to represent the diversity of driving behaviour.The refined cellular automaton model is used to describe the lower acceleration rate of a vehicle.The phase diagram and the capacity of the on-ramp system are investigated.The simulation results show that in the single cell model,the capacity of the on-ramp system will stay at the highest flow of a one lane system when the driver is moderate and careful;it will be reduced when the driver is aggressive.In the refined cellular automaton model,the capacity is always reduced even when the driver is careful.It proposes that the capacity drop of the on-ramp system is caused by aggressive lane-changing behaviour and lower acceleration rate.
In this paper,a new lattice hydrodynamic model based on Nagatani's model [Nagatani T 1998 Physica A 261 599] is presented by introducing the flow difference effect.The stability condition for the new model is obtained by using the linear stability theory.The result shows that considering the flow difference effect leads to stabilization of the system compared with the original lattice hydrodynamic model.The jamming transitions among the freely moving phase,the coexisting phase,and the uniform congested phase are studied by nonlinear analysis.The modified KdV equation near the critical point is derived to describe the traffic jam,and kink-antikink soliton solutions related to the traffic density waves are obtained.The simulation results are consistent with the theoretical analysis for the new model.
This paper modifies the weighted probabilistic cellular automaton model (Li X L,Kuang H,Song T,et al 2008 Chin.Phys.B 17 2366) which considered a diversity of traffic behaviors under real traffic situations induced by various driving characters and habits.In the new model,the effects of the velocity at the last time step and drivers' desire for acceleration are taken into account.The fundamental diagram,spatial-temporal diagram,and the time series of one-minute data are analyzed.The results show that this model reproduces synchronized flow.Finally,it simulates the on-ramp system with the proposed model.Some characteristics including the phase diagram are studied.
The full velocity difference model proposed by Jiang et al. [2001 Phys. Rev. E 64 017101] has been improved by introducing velocity anticipation. Velocity anticipation means the follower estimates the future velocity of the leader. The stability condition of the new model is obtained by using the linear stability theory. Theoretical results show that the stability region increases when we increase the anticipation time interval. The mKdV equation is derived to describe the kink-antikink soliton wave and obtain the coexisting stability line. The delay time of car motion and kinematic wave speed at jam density are obtained in this model. Numerical simulations exhibit that when we increase the anticipation time interval enough, the new model could avoid accidents under urgent braking cases. Also, the traffic jam could be suppressed by considering the anticipation velocity. All results demonstrate that this model is an improvement on the full velocity difference model.
