Trends and Impacts of Traffic Loading on the Northern Corridor Athi River – City Cabanas Highway Section, Kenya

Abstract

Deterioration of roads is among the major challenges facing Kenya's infrastructure sector. Pavement deterioration is mainly caused by traffic overloading and erratic climatic conditions. The Mombasa-Nairobi Highway known as A109 / A8 is a section of the Northern Corridor that connects Kenya's three major cities: Mombasa, Nairobi, and Kisumu and links the port of Mombasa to the entire East and Central Africa region. The road plays a major role in the region's economy by facilitating transportation to landlocked countries from the port of Mombasa. It is prone to premature deterioration in most of its sections. Overloading of vehicles consisting of local trucks mostly supplying building materials and long-distance heavy goods vehicles from the port of Mombasa to other East African countries is suspected to be a major cause of the premature deterioration which increases the pavement maintenance costs. This study investigated the trends and impact of traffic loading along the Northern Corridor Athi River - City Cabanas highway road section. The impact of overloading was determined from the remaining service life of the pavement due to overloading. Axle load measurements were carried out using a static axle weighing machine and mobile weighing machine along with visual inspection of the study section. The remaining service life of the pavement when subjected to overloading was estimated and compared to the pavement design service life. The fourth power rule was used to obtain the vehicle damaging factor which is a factor used to assess the extent of pavement destruction by a vehicle. The behaviour of transporters along the road section was also assessed by the use of questionnaires. The questionnaire investigated the transporters' knowledge of axle load limits, penalties and why the transporters still overload despite the measures to curb overloading Mombasa bound traffic was found to be prone to overloading with mobile weighbridge having the highest overload case. This led to an average of two years on the remaining service life of the pavement designed to last for fifteen years. The reduction in pavement service life leads to increased maintenance costs as the road will require major rehabilitation before the projected service period elapses. This, therefore, calls for the government to conduct mass education to inform transporters of the limits and penalties of overloading. The government in conjunction with truck manufacturers should also come up with better guidelines and regulations for truck body designs and axle configuration and direct SACCOs and transport companies to provide truck weighing machines at loading points to help verify gross vehicle weight.