San Ildefonso roundabout: peak volume and capacity

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Right: Partial schematic showing notation used for traffic volume data below. Each lane is represented by a letter (A-D) and a direction (in or out of circle).

The traffic volumes below are derived from video-tapes I made during the morning commute on 4/20/2011.
Above: Traffic volume for the various components of the roundabout. Above: Traffic volumes for the circle (A-in + B-in + C-in + D-in) and for the circle plus Bypass-DA. To compare these volumes with other roundabouts, make sure to understand what traffic conditions apply and what components are included.

The capacity estimated from the simple model discussed previously is about 1500 cars per hour. The peak seen here for the circle (excluding the bypass) is about 1100 cars/hr, so the utilization is roughly 70%, which seems plausible, given the qualitative features of the roundabout's actual performance.


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