| In all signalized intersection analyses performed with Highway Capacity Manual (HCM), the Pennsylvania Department of Transportation (PENNDOT) District 12-0 uses an ideal saturation flow rate of 1800 pcphgpl, which is less than the default value of 1900 pcphgpl provided by HCM. This is to account for the less aggressive characteristics of the local drivers. The purpose of this study is to field measure a sample of saturation flow rates, from which ideal saturation flow rates can be computed, in District 12-0 to determine the appropriateness of the lower ideal saturation flow rate. This study will scientifically test this hypothesis, along with measuring variations over the four-county District area, and variations during different weather conditions. Furthermore, it may be possible to provide anecdotal insight into potential shortcomings in the HCM saturation flow rate model, or the adjustment factors used therein.; In conclusion the use of an 1800 pcphgpl saturation flow rate was warranted when used district-wide, however a more localized usage of varying saturation flow rates would be recommended. In addition the HCM correction factors proved to be sufficient with the exception of the lane width correction factor which was determined to be inconclusive. Furthermore the rain study did show tendencies but was over all inconclusive. |
