Research On The Complex Characteristics Of Road Traffic Flow Based On Cellular Automaton Models

The controversy between fundamental diagram approach and three-phase traffic theory has not been resolved yet.The paper does not concentrate on which side is correct completely or building models within the framework of one side but finds correct aspects between two sides and deepens the understanding of traffic flow by proposing three new models.In the paper,the random probability of the VE model is modified to obtain a modified VE model that changes with the sum of the spacing distance and the virtual velocity of the front vehicle.The simulation results show that the fundamental diagram of the modified VE model is much closer to the measurement result and the modified VE model can simulate real single-lane highway traffic flow on a macroscopic level.A two-dimensional region is not the unique feature of synchronized flow and other congested traffic state can also have a two-dimensional region.The intermediate state between free flow and jams can exist steadily in the road system and form the independent traffic state.The methods that confirm the existence of synchronized flow concluding time-space plots,interruption effect,correlation function analyses are not accurate completely.In addition,the modified VE model can reflect the typical feature of real car-following behaviors.In the paper,the rule of deceleration range and the influence of the velocity difference of front and rear vehicles are added into the VDR model to obtain a new slow-start model.The simulation results show that small jams of the new slow-start model can exist steadily in the road system and these small jams have the tendency of synchronization.If a lot of vehicles that do not consider the comfortable driving and tend to decelerate rapidly exist on the road,free flow can be transited into jams directly.In the paper,the modified VE model is extended to the two-lane system to obtain a new two-lane model.The simulation results show that the change of the lane-changing frequency is irregular before the maximum of the lane-changing frequency.The lane-changing frequency will reduce rapidly after the maximum of the lane-changing frequency.The lane-changing behavior of long vehicles can hardly form moving traffic bottlenecks.Considering that the single-lane modified VE model simulates real single-lane highway traffic flow on a macroscopic level,has the two-dimensional region covered by scattering data points,simulates the features closer to that of synchronized flow,reflects the typical feature of real car-following behaviors and the two-lane modified VE model can simulate synchronized flow defined in three-phase traffic theory,the paper concludes that what complex models within the framework of three-phase traffic theory can simulate can also be simulated by simple models within the framework of fundamental diagram approach.The velocity adaption effect is uncertain to be realized in the single-lane system and the lane-changing behavior of vehicles in the two-lane system that want to achieve the desired velocity under the promise of security can be regarded as the cause of the velocity adaption effect of the two-lane system.