Material and Method: Data were extracted from the registry database of a cohort of workers in the Expressway Authority of Thailand between 2004 and 2011. Annual trends and changes in health status were described. Factors associated with major health problems were also evaluated.

Results: The cohort consisted of 2,000 to 2,700 workers. The trend of abnormal lung function, abnormal hearing, high blood pressure, high cholesterol, and asthma significantly increased over the period.Very few workers had high serum lead levels.

Conclusion: The present study revealed several major occupation-related health problems among transportation workers. In addition to an annual health assessment, other control measures should be instituted to protect workers from occupationrelated exposures.

Keywords: Expressway workers, Transportation, Health impact, Occupation-related, Prospective cohort