Performance Modelling for Botswana Gravel Roadways: Outcomes and Conclusions

Performance modelling of gravel roadways is required to predict the conditions in the future and provide information for optimal maintenance interventions. Roads are expensive asset and should be properly maintained regardless of their class or function to enhance their performance. Optimal maintenance interventions at the appropriate time to preserve the asset value are required. As improvement over previous methodologies, this paper modifies the logistic regression model by incorporating the ordinal nature of a dependent variable through defining the probabilities differently to develop improved gravel road performance models based on site specific data. The models reflect the history of gravel loss conditions to predict future performance for gravel roads in Botswana as a threshold to trigger optimal maintenance interventions. The input data for the models were generated from the triennial condition survey for Botswana carried out in 2002, 2005, and 2008. The developed improved gravel road performance methodologies are long term plans for preservation and maintenance as gravel road management systems in Botswana.