Development and Application of Sustainability Models for Unsealed Road Pavements

Abstract

Sustainability is a priority for most transportation and road agencies. Its measurement has progressed from a narrow environmental focus to the assessment of social, environmental, and economic outcomes. Although sealed-road sustainability assessment measures are available, measures have not been developed for unsealed road pavements despite the large networks of unsealed roads in many countries. The objective of this study was to develop models to capture sustainability measures for unsealed road pavements. This was done by relating unsealed road pavement characteristics to social (accidents and surface friction), environmental (emissions, dust pollution, and loss of resources), and economic (vehicle operating, accident, travel time, and maintenance costs) sustainability outcomes. Existing unsealed road surface characteristic prediction relationships, information presented in life-cycle cost analyses, and emissions studies were used to develop these models for rural unsealed roads. The models that were developed can be used in conjunction with existing pavement performance prediction models in life-cycle assessments, comparison of wearing course types, review of maintenance strategies, climate change consequence predictions, overall network sustainability performance reviews, and in pavement management. This paper contains a brief description of the approach, presents the models developed, and provides a number of examples of the application of the models to produce sustainability outcomes. The applications show that the models can effectively be used to quantify and compare sustainability outcomes. The applications highlight the dominance of aspects such as aggregate hauling distance in sustainability outcomes and the limitations of cost–benefit assessment procedures in which carbon emissions are not considered.