Relating the 2010 signalized intersection methodology to alternate approaches in the context of NYC conditions.

2013PDFTech Report49111-13-22Signalized intersectionsLevel of serviceHighway capacityManualsTraffic delaySaturation flowStarting (Driving)Field studiesResearch HubNew York Metropolitan AreaUnited StatesUniversity Transportation Research CenterPrassas, ElenaVin, ArthPolytechnic University (Brooklyn, New York, N.Y.)United States. Dept. of Transportation. Research and Innovative Technology AdministrationUS Transportation CollectionThe Highway Capacity Manual (HCM) has had a delay-based level of service methodology for signalized intersections since 1985. The 2010 HCM has revised the method for calculating delay. This happened concurrent with such jurisdictions as NYC reviewing the use of the HCM method in their environmental impact regulations (e.g. CEQR process), and concurrent with a dialog in the profession on when it is appropriate to use simulation models in lieu of HCM methods. This effort focused on providing guidance on how to use the 2010 HCM signalized intersection method in the context of the NYC urban environment. It was deemed important by NYCDOT to verify whether the delay and saturation flow estimates were consistent with what is found in the field in New York City, and specifically Manhattan. It was decided to measure and do analyses of the following measures of effectiveness: a. Saturation flow rate, b. Delay, and c. Start-up lost time. We began the process with meetings with NYCDOT staff to determine what data was available and what level of analysis they thought was needed. The HCM signalized intersection methodology is known to not work well in oversaturated conditions unless a multi-period analysis is done. Since the analysis that NYCDOT does with the HCM always uses a 15-minute period analysis and not a multi-period one, it was decided to only look at intersections that were not oversaturated when measuring and comparing delay results. The HCM 2010 arterial analysis methodology does consider queues and oversaturated conditions that should better reflect conditions in NYC, given that NYC is made up of arterial streets and not individual isolated intersections. However, the standard method used and required by CEQR is the signalized intersection methodology. This then was another factor in deciding not to use oversaturated intersections. It was found that the field data of saturation flow and delay were well correlated with the values computed using the 2010 Highway Capacity Manual methodologies, but that the start-up lost times that are defaulted and used in an HCM analysis are very different from the values measured in field data