Stress is an immense problem in modern society; approximately half of all occupational illnesses are directly or indirectly related to stress. The work of a bus driver is typically associated with high stress levels that negatively influence individual well-being as well as workforce management. The current study examined the impact of newly proposed working conditions on bus drivers' occupational stress by monitoring heart rate and by collecting data on mental workload with a questionnaire in operational driving conditions. The main determinants of stress levels were identified through multiple regression analysis. Results indicated that bus drivers experienced considerably lower stress levels under a new control strategy that shifts the performance objective from schedule adherence to service regularity. Higher stress levels were recorded during extreme weather conditions and peak hours and among inexperienced drivers. The measurements were performed with low-cost sports devices that can easily be used by practitioners.