Fuzzy cellular model for on-line traffic simulation

This paper introduces a fuzzy cellular model of road traffic that was intended for on-line applications in traffic control. The presented model uses fuzzy sets theory to deal with uncertainty of both input data and simulation results. Vehicles are modelled individually, thus various classes of them can be taken into consideration. In the proposed approach, all parameters of vehicles are described by means of fuzzy numbers. The model was implemented in a simulation of vehicles queue discharge process. Changes of the queue length were analysed in this experiment and compared to the results of NaSch cellular automata model.Comment: The original publication is available at http://www.springerlink.co

A Simplified Cellular Automaton Model for City Traffic

We systematically investigate the effect of blockage sites in a cellular automaton model for traffic flow. Different scheduling schemes for the blockage sites are considered. None of them returns a linear relationship between the fraction of ``green'' time and the throughput. We use this information for a fast implementation of traffic in Dallas.Comment: 12 pages, 18 figures. submitted to Phys Rev

A realistic two-lane traffic model for highway traffic

A two-lane extension of a recently proposed cellular automaton model for traffic flow is discussed. The analysis focuses on the reproduction of the lane usage inversion and the density dependence of the number of lane changes. It is shown that the single-lane dynamics can be extended to the two-lane case without changing the basic properties of the model which are known to be in good agreement with empirical single-vehicle data. Therefore it is possible to reproduce various empirically observed two-lane phenomena, like the synchronization of the lanes, without fine-tuning of the model parameters

Two-lane traffic rules for cellular automata: A systematic approach

Microscopic modeling of multi-lane traffic is usually done by applying heuristic lane changing rules, and often with unsatisfying results. Recently, a cellular automaton model for two-lane traffic was able to overcome some of these problems and to produce a correct density inversion at densities somewhat below the maximum flow density. In this paper, we summarize different approaches to lane changing and their results, and propose a general scheme, according to which realistic lane changing rules can be developed. We test this scheme by applying it to several different lane changing rules, which, in spite of their differences, generate similar and realistic results. We thus conclude that, for producing realistic results, the logical structure of the lane changing rules, as proposed here, is at least as important as the microscopic details of the rules

Effect of a consultation teaching behaviour modification on sleep performance in infants: a randomised controlled trial

The document attached has been archived with permission from the editor of the Medical Journal of Australia (09 January 2008). An external link to the publisher’s copy is included.Objective: To evaluate the effect of a behaviour modification program, taught to parents in a single visit to a trained nurse, in improving sleep performance in newborn infants. Design: Randomised controlled trial. Setting and participants: 268 families with normal newborn infants in the community, recruited between October 1996 and March 1997 from birth notices published in a South Australian daily newspaper. Intervention: A 45-minute consultation with a nurse 2–3 weeks after the birth, including a tutorial discussion on normal sleep patterns in newborn infants, supported by retained written material and, for infants with weight gain < 30 g daily, referral to their usual postnatal care provider. Main outcome measures: Hours of daytime sleep (0600–1800), night sleep (1800–0600) and total sleep per 24 h; and number of daily records with total sleep ≥ 15 h per 24 h, assessed by 7-day sleep diary at ages 6 and 12 weeks. Results: 268 families returned at least one sleep diary (137/171 intervention, 131/175 control), recording 3273 days. Two intervention infants were referred for low weight gain. Total sleep time was 15 h or more per 24 h on 62% of recorded days in the intervention group, compared with 36% in the control group (P < 0.001). At 6 weeks of age, intervention infants slept a mean 1.3 h per day more than control infants (95% CI, 0.95–1.65), comprising a mean 0.5 h more night sleep (95% CI, 0.32–0.69) and 0.8 h more daytime sleep (95% CI, 0.56–1.07). At 12 weeks, intervention infants slept a mean 1.2 h per day more (95% CI, 0.94–2.14), comprising 0.64 h more night sleep (95% CI, 0.19–0.89) and 0.58 h more daytime sleep (95% CI, 0.39–1.03). There was no significant difference in crying time between the groups. Conclusions: A single consultation supported by written material in the first 3 weeks of a child’s life improves sleep performance at 6 weeks of age. This improvement is maintained at 3 months.Brian G Symon, John E Marley, A James Martin and Emily R Norma

Generalized Force Model of Traffic Dynamics

Floating car data of car-following behavior in cities were compared to existing microsimulation models, after their parameters had been calibrated to the experimental data. With these parameter values, additional simulations have been carried out, e.g. of a moving car which approaches a stopped car. It turned out that, in order to manage such kinds of situations without producing accidents, improved traffic models are needed. Good results have been obtained with the proposed generalized force model.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm

Coherent Moving States in Highway Traffic (Originally: Moving Like a Solid Block)

Recent advances in multiagent simulations have made possible the study of realistic traffic patterns and allow to test theories based on driver behaviour. Such simulations also display various empirical features of traffic flows, and are used to design traffic controls that maximise the throughput of vehicles in heavily transited highways. In addition to its intrinsic economic value, vehicular traffic is of interest because it may throw light on some social phenomena where diverse individuals competitively try to maximise their own utilities under certain constraints. In this paper, we present simulation results that point to the existence of cooperative, coherent states arising from competitive interactions that lead to a new phenomenon in heterogeneous highway traffic. As the density of vehicles increases, their interactions cause a transition into a highly correlated state in which all vehicles practically move with the same speed, analogous to the motion of a solid block. This state is associated with a reduced lane changing rate and a safe, high and stable flow. It disappears as the vehicle density exceeds a critical value. The effect is observed in recent evaluations of Dutch traffic data.Comment: Submitted on April 21, 1998. For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.html and http://www.parc.xerox.com/dynamics

Modeling and Simulation of Multi-Lane Traffic Flow

A most important aspect in the field of traffic modeling is the simulation of bottleneck situations. For their realistic description a macroscopic multi-lane model for uni-directional freeways including acceleration, deceleration, velocity fluctuations, overtaking and lane-changing maneuvers is systematically deduced from a gas-kinetic (Boltzmann-like) approach. The resulting equations contain corrections with respect to previous models. For efficient computer simulations, a reduced model delineating the coarse-grained temporal behavior is derived and applied to bottleneck situations.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm

Macroscopic Dynamics of Multi-Lane Traffic

We present a macroscopic model of mixed multi-lane freeway traffic that can be easily calibrated to empirical traffic data, as is shown for Dutch highway data. The model is derived from a gas-kinetic level of description, including effects of vehicular space requirements and velocity correlations between successive vehicles. We also give a derivation of the lane-changing rates. The resulting dynamic velocity equations contain non-local and anisotropic interaction terms which allow a robust and efficient numerical simulation of multi-lane traffic. As demonstrated by various examples, this facilitates the investigation of synchronization patterns among lanes and effects of on-ramps, off-ramps, lane closures, or accidents.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm