Unique and innovative methodology for Roundabout Metering Signals

Eenie Creek Rd

We developed a unique method for modelling Roundabout Metering Signals for traffic and transport professionals around the world to solve complex problems for better roundabout operation.

SIDRA SOLUTIONS developed a unique method for modelling Roundabout Metering Signals for inclusion in its software as commissioned by VicRoads in Melbourne, Australia (equivalent of US Departments of Transportation). Innovation was essential to this major project as there was no analytical method available for practitioners to analyse metering signals.

Roundabouts with unbalanced flow patterns may have excessive delays and queuing on some approaches. Roundabout Metering Signals provide a practical and highly cost-effective technique that addresses this without the need for a fully-signalised intersection treatment. Large benefits are gained from this solution in terms of delay savings to the community with associated environmental savings, compared to fully-signalised intersections.

The project involved collection of survey data including video recordings of driver gap acceptance behavior, intersection turning movement volume counts, automated counting of circulating traffic, GPS-equipped floating car surveys, and metering signal timings. Using the survey data, the entering and circulating traffic characteristics were investigated at the controlling and metered roundabout approaches. These included queue lengths, delays and queue spacing on approach roads, critical gap and follow-up headways of entering drivers, bunching and headway distribution of circulating traffic as well as circulating vehicle speeds. This helped with the development of a complex analytical model by Dr Rahmi Akçelik combining roundabout and traffic signal capacity and timing analysis methodologies.

The Roundabout Metering Signals methodology developed was incorporated into SIDRA INTERSECTION. This software is now in use by over 2100 organizations with about 8700 licenses in 86 countries, including about 800 organizations with 2500 licenses in USA & Canada, helping practicing engineers and planners worldwide.

Based on a survey of US State Transportation Departments, Transportation Research Board document "Roundabout Practices" states that SIDRA INTERSECTION is the most widely-used software tool in the USA for roundabout capacity and performance analysis. Source:
Roundabout Practices, A Synthesis of Highway Practice, National Cooperative Highway Research Program, NCHRP SYNTHESIS 488, TRB, Washington, D.C., 2016


AKÇELIK, R. (2011). Roundabout Metering Signals: Capacity, Performance and Timing. Paper presented at the 6th International Symposium on Highway Capacity and Quality of Service, Transportation Research Board, Stockholm, Sweden, June 2011.

More innovative techniques in SIDRA INTERSECTION

SIDRA INTERSECTION includes a large number of innovative techniques representing one of the most advanced methodologies of any traffic design analysis package. This is based on 40+ years of award-winning research and development by the authors of the software, Dr Rahmi Akçelik and Mark Besley.

SIDRA INTERSECTION includes a full implementation of the roundabout capacity model described in HCM Edition 6. It offers powerful extensions to enhance roundabout design capabilities of the HCM model. These extensions are based on the innovative techniques developed by SIDRA SOLUTIONS over many years.