Assessing AASHTO and UK road design standards for use in most economic road designs in Uganda (a case study on Bugiri - Malaba road).

Abstract

In order to improve Uganda’s road infrastructure, the government has over the past few years committed large portions of its budget to the development of country’s road network. Basing on the study analysis of the study it was recommended that the use of the AASHTO pavement design model was more economic since it was based on the results of the road tests and the use of the structural number gave the exact thickness of the pavement layers. Pavement designs in Uganda are currently based on the UK spec road design model which is based on the traffic counts, ESALs traffic class, subgrade class computed from the CBR to obtain the pavement layer thickness to improve on the cost of pavement designs a new method of pavement design will be developed to design pavement thickness. The AASHTO design is an American system and is a regression method based on the results of road tests and utilizes the structural number (SN) to indicate the required combined structural capacity of all pavement layers over laying the subgrade The two pavement design models are good for pavement design specifications however the AASHTO design has proved to be more economical as compared to the UK spec as the former considers the exact pavement thickness based on the structural number intended to be achieved as opposed to the later that estimates pavement layer thickness based on a standard chart system Key Words Pavement layer thickness, AASHTO design, UK spec pavement design