Performance Evaluation of Pedestrian facilities at Donholm Interchange along outer Ring Road Nairobi.

Abstract

Under Vision 2030, the Kenyan government recognized transportation infrastructure as enabling fast economic growth. The development of transport infrastructure is fundamental to socio-economic transformation. In order to make Nairobi a center of development, an integrated and cohesive socio-economic infrastructure is crucial for further development. Critical to solving Nairobi's congestion and the problem of pedestrian transport service is investing in new road equipment and traffic management measures. Because the pedestrian environment is multi-dimensional, there are several aspects that influence the pedestrian's perception of comfort, security and convenience on the sidewalk setting. The physical infrastructure comprises of sidewalks, parking lanes, landscaped buffers, sidewalk width among others. The operational feature includes the traffic volume, speed limits and travel patterns. Thus, the analysis of Level of Service (LOS) is paramount in evaluating the real potential towards more sustainable lives. The project was in line with the objectives of the Performance assessment of pedestrian facilities at Donholm interchange along Outer Ring Road Nairobi. Specifically, the study sought to find out the pedestrian space provided at the sideways and sidewalks of the overpass, establish the pedestrian travel speed and find out the Level of Service. The study adopted the Highway Capacity Manual (HCM)-based LOS Method and the Pedestrian Level Of Service (PLOS) Model. The study considered literature from foreign and local manuals, previous studies, journals, articles, government policies and regulations, and other related documents. The study earmarked a section of Outer Ring Road, this being the Manyanja and Donholm overpasses for its field data collection process. This study adopted direct observation (manual count) to collect data on pedestrian traffic on the sidewalks of the study areas. Observation took place from a fixed elevated position to get a general view of the area of study. Site survey and visual inspections involved visually inspecting the sidewalks and measuring the provided walking spaces in terms of width and length. The study found out that the overpass serves on average 14,000-16,000 pedestrian in a whole day both directions combined. From the study 14,012 pedestrians used the overpass on Monday which was the lowest tally while 16,431 pedestrians were counted on Thursday which was the highest tally. The average time taken to cross the overpass of 60 m long was one-minute meaning that the walking speed 1m/sec which is slightly lower than the normal walking speeds of pedestrians in walkways. The spaces provided per pedestrian was found to be 0.04m2 which according to Hcm Model 2010 is described as LOS F and whose score is less than 25. This score represents the worst pedestrian facility at peak hours. The interaction between pedestrians and the vehicles is at the shoulders which also serve as the sidewalks with no designated busstops. This study therefore recommends construction of two-foot bridges of minimum 2 meters width parallel to the overpasses on both directions which was serious design omission. The foot bridges will improve the performance of the overpasses to the desirable peak period pedestrian flow of LOS C or above (TRB,2003; Orlando et al.,2003) and to a greater extend improve pedestrian safety at the interchange. Further recommendations include provision of lighting and signage at the overpasses.