Ohio Department of Transportation Office of Research and Development
Queuing occurs at intersections mostly due to overflow or inadequacy of turn bays. The ODOT L&D Manual Volume 1 has storage requirements for both signalized and unsignalized intersections. Figures 401-9E and 401-10E of the L&D Manual provide the required turn lane storage lengths which should be compared with the real world conditions to check for adequacy of these lengths as a measure of ensuring that accesses to the left turn lanes are not blocked. In addition to the projected turn lane volume, ODOT’s methodology incorporates both deceleration (based on the speed of the roadway) and potential blockage from the adjacent through lane. Currently, however, there are no records whether these storage lengths computed by the methodology put forth in this manual are valid and accurately represent the actual conditions at intersections in Ohio. This study used real world traffic and queue storage data at some intersections and analyzed these data to validate the model ODOT is currently using. This study used the observed field data to evaluate the ODOT’s model of storage length at intersections. In addition, the queue storage lengths observed from field data were compared with the prediction results of HCS and SYNCHRO computer packages. The model evaluation task evaluated the level of precision of each of the three models (ODOT, HCS, and SYNCHRO) with respect to the field data observation. L&D Manual lead the way by accurately predicting the observed queues by about 81.6% and closely followed by HCS, which also had a 79.2% prediction accuracy. SYNCHRO was by far the lowest with a 46.0% prediction accuracy.
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Eustace, Deogratias and Ponnada, Sowjanya, "L&D Manual Turn Lane Storage Validation/Update" (2012). Civil and Environmental Engineering and Engineering Mechanics Faculty Publications. 66.