Drivers’ lane changing violations at a curbside bus stop on an undivided three-lane roadway were investigated. Logit models were developed to determine contributing factors to the violations. Bicycle lane presence, low opposing traffic volume and longer bus dwell time at a bus stop were associated with a higher probability of a lane changing violation by drivers waiting behind the stopped bus. More violations were observed on one-way left-turn lanes than two-way left-turn lanes during the study period. By combining various opposing traffic volumes and bus dwell times, a guidance chart of a lane-changing violation probability was developed, which can be applied when determining types of bus stops, their placement, and when developing safety programs for safer and better mobility on three-lane roadways. This study can be a valuable resource in improving safety and mobility program at bus stops on three-lane roadways because three-lane roadways are being used more often as part of sustainable surface transportation programs such as road diets.