Weather-related crashes represent a significant concern in roadway safety. Wet collisions often resulted in injuries or fatalities, at a ratio higher than collisions that occur in dry roadway conditions. Therefore, it is of strong interest to identify and manage the locations where collisions are prone to happen under wet pavement surface or adverse weather conditions. This paper introduces a method to estimate precipitation exposure of roadway segments by linking weather station data to collision database. Subsequently, the corresponding crash rate for a subject location is calculated based on the concept of conditional probability. The method is then applied to quantify and compare the wet collision rates of some study sites before and after pavement projects of installing Open Graded Asphalt Concrete (OGAC), a pavement countermeasure commonly adopted for wet collision reduction. The findings demonstrated that OGAC offered the reduction of wet collisions at a large fraction of the study sites.