Comparative evaluation of roundabout capacities under heterogeneous traffic conditions

Abstract

In heterogeneous traffic conditions, roundabout capacity is described by vehicle and driver characteristics which are different from traffic conditions in homogeneous conditions. In the present study, the capacity of the roundabout is determined using various capacity formulas such as gap acceptance models given by Highway Capacity Manual 2010 (US), German model (2001); empirical regression models given by TRRL (UK) and weaving models given by IRC: 65-1976 (India). In addition, microscopic simulation model like VISSIM (PTV Germany) is also used to derive capacity values. Unlike the other capacity estimation models, VISSIM is helpful in estimating capacity values using geometric and driver characteristics and it can also simulate heterogeneous traffic condition accurately. Capacity is estimated after calibrating the simulation model (VISSIM) developed for the roundabout. This is achieved by incorporating different vehicle classes to represent the heterogeneous traffic environment, driver gap acceptance, and lane change parameters. All the required inputs were extracted from the video using semi-automatic data collection methods. Data are used for the estimation of capacity values from different methods mentioned above and for the calibration and validation of simulation model. The capacity values estimated form various formulas except German model are distinctly different from the field values and they are either overestimating or underestimating. Analysis of these observations reveals that the capacity values from VISSIM and German models are nearly matching with the field capacity.

Calibrating HCM model for roundabout entry capacity under heterogeneous traffic

“…The HCM 2000 is one of the popular models of roundabout entry capacity based on gap acceptance. In the 2010 version of the Highway Capacity Manual, a detailed procedure was developed for estimating the entry capacity of roundabouts in the USA [14]. HCM 2010 suggests use of Eq.…”

Using Analytical Models to Calibrate a Dual-Roundabout Intersection in Microsimulation

“…Most of these studies rely on the VISSIM simulation platform [5] while the rest use other available tools (such as Sidra [6] and cellular automata models [1]). The VISSIM-related studies mostly focus on three key parameters, including: 1) Priority Rules or Conflict Areas that define the operational logic within roundabout and control the critical gap acceptance behavior; 2) Reduced Speed Areas, that provide speed control for circulating and inbound traffic; 3) Wiedeman 74 and Wiedeman 99 car following models that emulate driver and car following behaviors [2], [4].…”

Exploring the uncertainty in capacity estimation at roundabouts

“…In transportation engineering, despite considerable information can be derived from new technologies and can be incorporated into the traditional performance measurements (see e.g. [2][3][4][5][6][7][8]), the effect of variability and uncertainty in input parameters on outputs is not often taken into account in the capacity analysis of roads and intersections. The assessment of the effects of a design choice on one or more parameters that are used when an operational analysis is being carried out, requests information on the sources of uncertainty that have affected them and the relation among them [9].…”