Modeling stochasticity of heterogeneous traffic
21 Sep 2003-pp 160-165
TL;DR: In this paper, a stochastic traffic-flow simulation model for urban highways with heterogeneous traffic is presented, based on the randomness inherent in road user (driver) and vehicular characteristics.
Abstract: The important aspect that makes the nature of traffic flow stochastic is the randomness inherent in road user (driver) and vehicular characteristics. We give an overview of the development, validation and use of a stochastic traffic-flow simulation model for urban highways with heterogeneous traffic. An appropriate methodology for the collection and extraction of headway data has been suggested. The headways of urban mixed-traffic dominated by smaller vehicles like motorized two-wheelers can be modeled using negative exponential distribution over a wider range of traffic flow. An attempt has also been made to model the traffic flow on a road stretch with bus stops. The random natures of the arrival pattern and dwell time of the buses have been suitably incorporated
Citations
More filters
20 Sep 2006
TL;DR: The development and validation of a stochastic heterogeneous traffic-flow simulation model for an urban single-lane two-way road, with controlled intersection, and the interaction between vehicle types during manoeuvres at the intersection are described.
Abstract: The characteristics of heterogeneous traffic (with variation in vehicle length) are significantly different from those for homogeneous traffic The present study describes an overview of the development and validation of a stochastic heterogeneous traffic-flow simulation model for an urban single-lane two-way road, with controlled intersection In this paper, the interaction between vehicle types during manoeuvres at the intersection are analysed in detail Two different motorised vehicle types are considered, namely cars and buses, (or similar length vehicles) A two-component cellular automata (CA) based model is used Traffic flow data, captured manually by Dublin City Council at a local intersection, are analysed to give a baseline on how the distribution of short and long vehicles affect throughput It is anticipated that such detailed studies will aid traffic management and optimisation strategies for traffic flow.
12 citations
References
More filters
TL;DR: In this article, four groups of capacity estimation methods, namely, headway distribution, bimodal distribution, selected maxima, direct probability and product limit, are compared.
Abstract: Capacity is a central concept in roadway design and traffic control. Estimation of empirical capacity values in practical circumstances is not a trivial problem; it is very difficult to define capacity in an unambiguous manner. Empirical capacity estimation for uninterrupted roadway sections has been studied. Headways, traffic volumes, speed, and density are traffic data types used to identify four groups of capacity estimation methods. Aspects such as data requirement, location choice, and observation period were investigated for each method. The principles of the different methods and the mathematical derivation of roadway capacity are studied and discussed. Among the methods studied are the headway distribution approaches, the bimodal distribution method, the selected maxima, and the direct probability method. Of the methods based on traffic volume counts, the product limit method is recommended for practical application because of sound underlying theory. An example of the application of this promisin...
162 citations
TL;DR: INTELSIM moved vehicles simultaneously and produces solutions for a continuous time frame and produced the best agreement with the field data and required the least amount of calibration effort.
Abstract: Presented in this paper are the car-following methods and algorithms of the NETSIM, INTRAS, FRESIM, CARSIM, and INTELSIM models. Moreover, the car-following performance of these models is compared with the field data. NETSIM, INTRAS, FRESIM, and CARSIM car-following models first move the leader and then update the follower in one simulation time step. Because of this approach, these car-following models cannot be used to command vehicles in real-time intelligent transportation systems applications. Moreover, brake reaction times are limited by the simulation time step because of this method of updating the vehicles. INTELSIM was developed to overcome these deficiencies. INTELSIM moves vehicles simultaneously and produces solutions for a continuous time frame. INTELSIM produced the best agreement with the field data and required the least amount of calibration effort.
128 citations
TL;DR: A comprehensive review is presented of the few studies on mixed, non-lane-based traffic in India, Bangladesh, and Indonesia and the unique characteristics of traffic composition, driver behavior, roadway geometry, maneuverability, and vehicular interactions are presented.
Abstract: The composition of traffic in developing countries is mixed, with a variety of vehicles, motorized and nonmotorized, using the same right-of-way. The motorized or fast-moving vehicles include passenger cars, buses, trucks, auto-rickshaws, scooters, and motorcycles; nonmotorized or slow-moving vehicles include bicycles, cycle-rickshaws, and animal-drawn carts. The proportion of slow-moving vehicles in the traffic stream may vary from 10 to 80 percent. Since the 1950s, considerable research has been done to develop traffic flow models for roadways with mainly motorized vehicles or homogenous traffic, representing the composition of traffic primarily in industrialized countries. A review of the literature has shown that limited studies have been done to develop an understanding of traffic flow for non-lane-based heterogeneous or mixed traffic conditions in developing countries. Some efforts have applied a variation of practices developed for homogenous traffic by converting heterogeneous traffic to equivalen...
121 citations
TL;DR: In this article, the authors evaluated the impact of traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on passenger car equivalents (PCEs) for different truck types for the full range of traffic conditions on freeways, two-lane highways and arterials.
Abstract: Passenger car equivalents (PCEs) have been used extensively in the Highway Capacity Manual to establish the impact of trucks, buses, and recreational vehicles on traffic operations. PCEs are currently being used for studying freeways, multilane highways, and two-lane highways. A heavy-vehicle factor is directly given for the impact of heavy vehicles at signalized intersections (and indirectly along arterials). These PCE values are typically based on a limited number of simulations and on older simulation models. In addition, the impact of variables such as traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on PCEs has not been evaluated in depth for all facility types. The methodology for developing PCEs for different truck types for the full range of traffic conditions on freeways, two-lane highways, and arterials is described. Given the scope of this research and the variability of traffic conditions to be examined, simulation was selected a...
119 citations
TL;DR: In this paper, the authors studied the headway between vehicles in a traffic stream and found that the Erlang distribution provided a good fit to the observed headways at sites with high traffic flows.
Abstract: The headway between vehicles in a traffic stream is of fundamental importance in traffic engineering applications. Previous research in this subject has focused on modeling theoretical distributions for low and medium traffic flow conditions. Yet little research has studied congested traffic conditions—that is, the high traffic flow state. In the same context, there appears to be a lack of clear-cut boundaries for the three flow states (low, medium, and high). This study attempts to determine such boundaries on the basis of traffic conditions observed at the study sites. Although observed headways at arterial sites follow a gamma distribution, distributions that fit freeway headways differ according to the traffic flow state. The Erlang distribution provided a good fit to the observed headways at sites with high traffic flows.
90 citations