Calibration of Robertson’s Platoon Dispersion Model in Non-lane Based Mixed Traffic Operation

Abstract

Once released from a signalised stop-line, vehicles normally proceed to the next intersection in bunches (called as 'platoon'). While moving along a corridor, vehicle platoons disperses and therefore, the pattern of vehicle arrivals at a signal is different from the pattern of discharge from its upstream signal. Modelling of dispersion of vehicle platoon is an important consideration for coordinated operation of closely spaced traffic signals. In this regard, Robertson's dispersion model has significant contribution towards design of coordinated signal system. However, successful application of Robertson's model largely depends on calibration of the model for local roadway and traffic conditions. In this paper, calibration of Robertson's model is carried out for an urban roadway scenario in India giving due consideration to level of heterogeneity in vehicle mix, variation in travel demand and link travel time. Data are collected from an urban arterial in Kolkata metropolitan area using videography. Using Robertson's platoon dispersion model, downstream arrivals are predicted for observed upstream flow profiles at stop-line. Then, parameters of the Robertson's platoon dispersion model (a and b) were calibrated using best fit approach. An empirical model is developed to express platoon dispersion factor (a) as a function of vehicle composition, normalised flow (flow to capacity ratio at stop-line), link travel time and modelling step size.

A New Vehicle Arrival Prediction Model for Adaptive Signal Control in a Connected Vehicle Environment

“…Considering the impact of the number of lanes, Bie et al proposed a new method to calibrate the platoon dispersion parameter [10]. In mixed traffic flow, Paul et al developed a new method to estimate the parameter of Robertson's model [4], [5]. Therefore, these studies are platoon-dispersion-based vehicle arrival prediction models, which use the fixed loop detectors data to calibrate parameters, then predict vehicle arrivals.…”

“…In the past few decades, a multitude of methods have been proposed for vehicle arrival prediction. There are two main categories: One predicts vehicle arrivals based on platoon dispersion theory [4]- [12]. The platoon-dispersion-based model predicts vehicle arrivals based on the vehicle departure and arrival data from the fixed loop detectors, which locate at upstream and downstream intersections.…”

Dynamic platoon dispersion model based on real‐time link travel time

“…Most subsequent studies focused on calibrating the parameters of Robertson's model [5][6][7][8][9][10]. Day and Bullock [6] calibrated Robertson's model with high-resolution signal event data.…”

“…The statistical results verified that the platoon dispersion factor dependeds on the number of lanes. Paul et al [9,10] studied Robertson's platoon dispersion model in nonlane based mixed traffic operation and proposed a new approach for calibrating Robertson's model. However, in recent years with a gradual increase in the number of vehicles, urban traffic congestion increasingly aggravated.…”

“…Previous studies of platoon dispersion model mainly focus on two aspects: (i) new methods to calibrate Robertson's platoon dispersion model under different traffic condition [5][6][7][8][9][10] and (ii) new heterogeneous platoon dispersion models based on the mixed probability distribution [11][12][13][14]. However, all these studies [5][6][7][8][9][10][11][12][13][14] were based on historical data, which cannot effectively capture the dynamic characteristics of traffic flow. In urban roads, the real-time traffic flow changes due to complex conditions, such as weather, accident, time, work zone, and so on [15][16][17].…”