In 2015, there were 6.3 million crashes reported across the nation, including 35,092 fatalities and 2.44 million injuries, according to NHTSA. More than half of the 2015 fatalities were roadway departure crashes.
Often, a small subset of the total highway network is responsible for a significant percentage of certain crashes types. In 2015 for example, 23 percent of fatal crashes occurred on horizontal curves, according to FARS, yet horizontal curves make up only 5 percent of our Nation's roadways.
A roadway must have an appropriate level of pavement friction to ensure that drivers are able to keep their vehicles safely in the lane. Poor pavement conditions, especially wet pavement, have been identified as one of the major contributing factors in roadway departure crashes. When a pavement surface is wet, the level of pavement friction is reduced, and this may lead to skidding or hydroplaning.
Vehicles have different friction demands depending on the characteristics of the roadway. For example, a vehicle traversing a horizontal curve requires a greater level of friction than vehicles on a straight section. Common locations that require higher friction values are horizontal curves, steep grades, or intersection approaches. As a result of the increased friction demand, the roadway surface at these locations often becomes prematurely polished, reducing the pavement friction and contributing to higher crash rates. Excessive speeds or distracted driving can also contribute to the crash rates in areas where friction demand is high.
Research conducted by the National Transportation Safety Board and FHWA indicates that about 70 percent of wet pavement crashes can be prevented or minimized by improved pavement friction.
Pavement friction is critical for changing vehicle direction and ensuring the vehicle remains in its lane. Traditional friction courses or high friction surface treatments should be considered for curves with numerous wet weather crashes or severe curves with higher operating speeds.