Developing performance models for treated gravel roads to evaluate the cost-effectiveness of using dust chemical treatments

The objective of this study is to develop a long-term performance model to predict the service life of treated gravel roads. Fugitive dust emissions from 11 recently treated gravel roads located in five different counties in the state of Wyoming were measured periodically for 12 months. Visual survey ratings of the 11 roads were taken each time. Surfacing moisture samples were collected. Traffic speeds and volumes by class were also collected using a two-tube traffic counting system. Surfacing aggregate samples were collected and their gradations were determined. Performance curves were developed for each of the selected 11 roads. A comprehensive long-term performance model was developed that predicts the service life of treatment on gravel roads. A life cycle cost analysis comparison study was also conducted to compare the cost of maintaining untreated gravel roads with the cost of maintaining treated gravel roads. Statistical analyses generated regression models that allowed the prediction of factors significant to the service life of treatment on gravel roads. It was found that the daily traffic, the percentage of fines in the soil and the annual rainfall had the highest contribution to road deteriorations and increase in dust generation. Dust treatment was found to have a service life of one year before dust emission rates went back to before treatment levels. The life cycle cost analysis indicates that the initial cost of applying dust suppressant treatment to gravel roads is expensive. However, it will increase the road service life and significantly reduce dust generation.