Study on the Effects of Pavement Condition on Level of Service of the Road Segments

The study was conducted to investigate effects of pavement condition index on level of service of the road segments in Mbeya region Tanzania. Field measurements of vehicle speeds, vehicle volume, lane width, should width, vertical grades and side clearance, were conducted for the purpose of determining level of services (LOS) of the road segments. Pavement defects were identified and defects quantities and severity were measured and analyzed for the purpose of determining pavement condition indices (PCI). For this study five two-lane class III highway road segments were analyzed to determine LOS and PCI.  The results indicated that LOS for the road segments ranged from C to E. LOS C was for Mwahala–Igawilo road segment, LOS D was for Kabwe–Isanga and Uyole–Nanenane and LOS E was for Mbalizi–Ifisi and Iwambi–Mbalizi. The LOS C is characterized by restricted flow and level of comfort and convenience are noticeably declining and LOS E is unstable flow at or near capacity with poor levels of comfort and convenience. In order the vehicles to operate at high level of comfort and convenience the road geometric features of the road segments for this study needs to be upgraded to meet minimum requirements but also introduction of climbing lanes in areas with steep slopes. For pavement condition, the current PCI rating for Mwahala–Igawilo was determined to be good, for Kabwe–Isanga and Uyole–Nanenane was fair and for Mbalizi–Ifisi and Iwambi–Mbalizi was very poor. From the PCI rating it was investigated that, Mwahala–Igawilo road segment requires preventive maintenance, for Kabwe – Isanga and Nanenane – Uyole requires rehabilitation and for Mbalizi–Ifisi and Iwambi–Mbalizi requires major rehabilitation or reconstruction.   The effect of pavement condition on LOS for this study is expressed in equation as PFFS = 0.243PCI + 55.5 where percentage free flow speed (PFFS) is the measure of LOS for two lane class III highways. From the equation it is indicated that as pavement condition deteriorate, the LOS is also deteriorate. It is important to incorporate pavement condition in the determination of LOS of the road segments