The purpose of this paper is to determine the critical factor in human error that contributes towards express bus accidents. Three main attributes in human error are discussed, which are physical, mental and experience. Thus, this research aims in finding the highest contributor in human error and the main concern in road safety regarding express bus. This research was conducted in which a user opinion and experience on factor causes express bus accidents is accounted with a total of 287 respondents which consist of bus driver, bus passengers or victims, firemen, police officer, express bus management companies and officers of road safety agency participated. The factor analysis method was utilised and the factors attributing to human error was extracted and interpreted. This research indicates that physical, mental and experience attributes of the express bus driver do contribute in human errors towards accidents. It was found that mental attributes of the bus driver has high effect on contributing to human error towards express bus accidents and driver’s sleepiness was the biggest concern in the express bus accident causes. Other attributes were discussed more in this paper and somehow provide an interesting insight of plausible cause of express bus accident.