Identification of the Impact on Road Roughness on Speed Patterns for Different Roadway Segments

Pavement surface condition is one of the factors that affect driver comfort, operation speed, service volume, and traffic safety. Even though several studies have conducted recently to find the effect of different roadway characteristics on traffic stream performance, not many were focused on the impact of road roughness on operating speeds. Therefore, this research will investigate the impact on road roughness on speed patterns for different roadway segments under different flow levels. The unevenness of a road is measured as road roughness and it has been globally accepted as a metric to evaluate the pavement condition and it relates to the conditions perceived by the road users. In addition to the user discomfort, rough roads would result in, speed reduction and an increase in vehicle operating costs. International Roughness Index (IRI) measured by smartphone application is used as the indicator for road roughness in this study. The effect of road roughness is investigated at Free Flow Speed (85
^th
percentile speed) and 50
^th
percentile speed which is determined using the speed distributions that occurred during specific time intervals. Further, the abovementioned behavior is analyzed separately for junctions, mid-block sections, and horizontal curves to represent different roadway conditions.