Motorcyclists1 are the fastest-moving vulnerable road users, which made them overrepresented in road injuries and fatalities. In Taiwan, motorcyclists account for approximately 60% of total road fatalities each year, but little is known about the prevalence of risk-taking behaviors among motorcyclists. In the present study, a roadside observation was carried out to examine their unsafe riding behaviors, such as secondary task engagement, helmet non-use, and traffic violations. 4030 motorcyclists were observed at three signalized intersections in Tainan, Taiwan: 593 in a residential district, 1034 in a business park, and 2403 in the city center. 7.3% of them were engaged in at least one secondary task, with phone use (3.5%) being the most common one, followed by chatting with others (1.6%). Although nearly all riders were helmeted (98.9%), the majority of the riders used non-standard helmets: 65.2% wore an open-face helmet, 21.0% half helmet, and only 12.6% full-face helmet. 5.9% of all motorcyclists were observed breaking at least one traffic rule at the intersections, and the violations that occurred the most often were turn signal neglect (2.8%) and red-light running (2.6%). These risky riding behaviors were also associated with contextual variables and rider characteristics. The likelihood of distracted riding increased at a red light, in the city center, when riders were younger, male, delivery workers, and riding with an adult passenger. Traffic violations were more frequent in the city center, in the afternoon, and on a two-lane road. Furthermore, risk-taking behaviors were more prevalent in un-helmeted riders. Observations in different weather conditions, more traffic contexts, and locations are recommended for future studies to further understand their impact on motorcyclists' adaptive riding behaviors.