AROUND - Improving Capacity And Emission Models of Roundabouts
Overview
Background & policy context:
During the last three decades, roundabouts have gained increased popular and political acceptance and are now used worldwide. Roundabouts are known by their high performance levels in safety, traffic capacity and in atmospheric emissions, especially when compared with other at-grade intersections.
Objectives:
This research was focused on using appropriate modeling methodologies to understand the effects of turbo-roundabouts (innovative roundabout where lanes are bounded by traffic signs and raised curbs placed at entering and circulating lanes) on capacity, safety and emissions, in comparison with conventional single-lane and double-lane roundabouts.
Methodology:
AROUND focused on the demand for sound analytic and simulation roundabout models. On site work using an equipped vehicle, video cameras, pneumatic tube detectors and viacounts to measure speed and count vehicles was carreid out.
The work comprised five main parts:
- Collection of geometric, traffic and pedestrian data for a set of sites covering a wide range of geometric and operational characteristics;
- Comparative assessment and improvement of existing analytic capacity models, either regression or gap-acceptance based;
- Calibration of microscopic simulation models, with emphasis on the sub-models directly associated to driver behaviour at roundabouts (car-following and gap-acceptance);
- Association of a pollutant emission model with the microscopic models. The estimation of the pollutant emissions will be supported by the Vehicle Specific Power (VSP) concept, which correlates the vehicle speed profiles with the respective consumptions and emissions;
- Application of the improved capacity and pollutant models to test the efficacy of new solutions, such as the turbo-roundabout, now very popular in Netherlands.
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