Accumulation of stormwater on road surfaces causes pavement damage as well as traffic accidents. For these reasons, stormwater is removed from road surfaces using engineered drainage systems. The drained stormwater undergoes some form of treatment prior to discharge into the environment. Vehicles have been noted as a source of stormwater pollution due to the deposition of various pollutants by automobiles on roads and parking lots. These pollutants include chemicals that are present in automobile lubrication oils, antifreeze, gasoline, tire wear and automobile braking systems as well as particulates from the exhaust system. During rain fall events, these pollutants are washed from the road surface and are carried by stormwater runoff into soils, groundwater and surface water. Transportation agencies in the United States are required by the Environmental Protection Agency (U.S. EPA) to comply with the National Pollution Discharge Elimination Standard (NPDES), including planning and design permit requirements for the treatment of stormwater runoff to ensure that rainwater runoff from roads (including local, states, and federal roads) do not carry pollutants into waterways such as rivers, creeks, lakes, and streams. To comply with U.S. EPA requirements, transportation agencies must install stormwater BMPs to capture and treat stormwater runoff from road surfaces. One of the BMPs is the use of permeable pavements that allow stormwater to move through the pavement layers (away from the road surface) where it can either infiltrate into the soil and groundwater, or drain to the road shoulder where it is collected for treatment as needed. Concerns have been raised about structural strength of permeable pavement. With an abundance of reports on various types of permeable pavement, there is a need to classify permeable pavement in a uniform manner that will allow for easy identification of the key structural material and suitable application for various traffic requirements. Uniform classification and naming of permeable pavement is important, as the application of permeable pavement ranges from pavers that are used for pedestrian sidewalk and walkways to permeable “asphalt” friction course that is used as a thin top layer of highway pavement. The primary objective of this project is to conduct a review of the literature to determine the state of the art on (1) the effect of stormwater on defect of road surfaces (pavement), (2) traffic safety issues associated with highway stormwater, (3) the use of permeable pavement in the management of highway stormwater for various traffic requirements, and (4) the identification of gaps in the existing literature for further research. This research includes a review of the literature on the use of permeable pavement in highway stormwater management and traffic safety issues associated with highway stormwater, as well as recommendations for further investigations. The primary focus of the research was to conduct a comprehensive review of the literature on environmental pollutants in highway stormwater. The literature was also reviewed on the impact of road stormwater on traffic safety and on the management of roadway stormwater using permeable pavement, including the types of permeable pavement and their structural design components. The research was motivated by a report in the literature on adapting full-depth permeable pavement for highway shoulders for stormwater runoff management. The goal was to review the types of permeable pavement to identify their suitability for use in highway shoulders that are often used by heavy vehicles under relatively high speed. To this end, an extensive online literature search was conducted using the Google search engine. The literature search produced the following themes for the research report: 1. Environmental pollution associated with highway stormwater; 2. Stormwater removal from road surfaces; 3. Highway stormwater BMPs; 4. Stormwater impact on durability of pavements; 5. Road safety impact of accumulated stormwater on pavement surfaces; 6. Types of permeable pavements used in sustainable management of highway stormwater; 7. Permeable friction course in highway stormwater BMPs; and 8. Use of roadway shoulders in stormwater management and safety implication. Examples of key words and phrases used in the online searches include permeable pavement, types of permeable pavement, effect of stormwater on pavement durability, highway stormwater runoff, highway stormwater quality, highway stormwater management, highway stormwater infiltration, road cross-section and stormwater drainage system, asphalt pavement defects, concrete pavement defects, effect of stormwater on pavement skid resistance, hydroplaning, highway shoulder, sustainable highway stormwater management, and effect of stormwater and wet pavement on road safety. (Author/publisher)
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