Free Flow Speed Analysis of Two Lane Inter Urban Highways

Increasing vehicular traffic which demands development of road network length has been observed for the past many decades on Indian roads. In addition to this, improper road maintenance strategy has resulted in pavement failure causing disintegration and deterioration before the design life of pavement. This deterioration of pavement results in reduced Free-Flow Speed (FFS) and loss of roadway capacity. United States Highway Capacity Manual (US-HCM 2010) defined Free Flow Speed is the theoretical speed when density and flow rate on a study segment are both zero. One of the objectives of this study is to review various factors influencing FFS and various methods of estimation of Free Flow speed for Inter Urban two lane roads. Based on the literature review, it was found that the five principle parameters influencing the free flow speed are driver, vehicle, roadway, environmental related parameters, traffic operation and control related parameters. This study also reviewed various methodologies adopted for determining FFS considering these influencing parameters. This study developed a relationship between free flow speed and pavement distress parameters. In this regard, traffic data was collected by using video for 8 hours on a identified trap length (60mts) covering Two lane bidirectional inter-urban road sections in Haryana and Andhra Pradesh states. The study period encompassed 4 hours in the morning and 4 hours in the evening hours. Classified Traffic volume count coupled with entry and exit time of different vehicles was extracted on identified trap length at every five minute interval. The pavement distress data collected for the study sections was collected using Automated Road Survey System(ARSS). Based on the above collected data appropriate relationships between Roughness and Free Flow speed were formulated. Linear models were considered to develop the Free Flow Speed Equations for the study sections and these equations were validated on statistical grounds too. (C) 2016 The Authors. Published by Elsevier B.V.