Riding quality affects the vehicle speed, which affects travel time for road users. The International Roughness Index (IRI) is commonly used to describe road roughness. In previous studies, scholars used simulation models to perform regression analysis of IRI and traveling speed. However, simulation models cannot reflect actual traffic conditions and the experiment sample sizes in most studies are small. This paper analyzes the relationship between IRI and free-flow speed through the measured IRI data and traffic data of Shanghai Urban Expressway over three years. The results show that there is a significant linear relationship between IRI and free-flow speed change. For sections with different lanes, the relationship is different. When the IRI is increased by 2 m/km, the free-flow speed of 2-lane section is reduced by 3.2 km/h, and the 3-lane section is reduced by 1.6 km/h.
The Influence of the Road Roughness on Free Flow Speed—A Case Study of Shanghai Urban Expressways
21st COTA International Conference of Transportation Professionals ; 2021 ; Xi’an, China
CICTP 2021 ; 2439-2448
2021-12-14
Conference paper
Electronic Resource
English
Traffic Flow Capacity Model for Urban Expressways
ASCE | 2010
|Engineering Index Backfile | 1955