Environmentally Optimized Design for Low-Volume District Roads in Tanzania

Abstract

A demonstration project was carried out on district roads in the Bagomoyo and Siha Districts of Tanzania. Funds available for upgrading the roads were not sufficient to provide bitumen or concrete surfacing over the full length, and traffic levels did not justify this level of investment. An environmentally optimized design approach, by which different solutions were applied to each section of road in response to local conditions, had to be adopted. This approach included earth- and gravel-surfaced options where the existing road was stable. The opportunity was taken to demonstrate a range of road surfacing options (bituminous and non-bituminous) so as to obtain data on their life-cycle costs, acceptability to road users, and likely durability over the life of the road. Pavement design was based on recent innovations for low-volume sealed roads in the region, including the use of the dynamic cone penetrometer method. Conclusions highlight a number of bituminous pavement options found to be more economical than regraveling. In addition, economic and social benefits, in lower maintenance and labor-based construction, result from using concrete paving blocks and concrete pavements.