Turn signal neglect is considered to be a key contributor to crashes at intersections, yet relatively little research has been undertaken on this topic, particularly in developing countries. Using a case study of Vietnam, this research aimed to explore the role of environmental characteristics, perceived risk, beliefs and lifestyle behaviours on the frequency of turn signal use at intersections. A self-administered questionnaire was distributed to motorcyclists (n = 527) and car drivers (n = 326) using online and offline methods. Using partial least squares structural equation modelling (PLS-SEM), key findings indicate that perceived risk, beliefs and environmental characteristics play a significant role in affecting the frequency of turn signal use among motorcycle riders and car drivers at intersections. While lifestyle behaviours were not found to be a good predictor of turn signal use among car drivers, they were found to indirectly affect turn signal use among motorcycle riders through the mediation of beliefs and perceived risk. The findings can help inform the development of more targeted measures to increase turn signal use.@en