This study proposes to manage risk related to scheduling in highway projects using the program evaluation and review technique (PERT) combined with the critical path method (CPM) and compared with the Monte Carlo simulation technique during the project planning phase. These methods also aim to reduce unnecessary waste of wages, machinery costs, and environmental pollution from the construction project. The research collected data such as daily reports of reinforced concrete pavement construction projects in Chiang Mai, each 500  m long. All 25 projects in 25 sub-districts must reflect activities and procedures. The results showed that the completion date should be achieved within 63 days based on PERT/CPM. On the other hand, after 10,000 times dummy with the Monte Carlo simulation technique, the most accurate completion date shows that the project will be completed within 61 days. From the comparison of the results of both methods and techniques, the completion date with the Monte Carlo simulation was earlier than the completion date of the PERT /CPM method. The result of the completion date from the Monte Carlo simulation indicates that the redundant costs of workers, wages, and machinery usage, as well as the pollutant emissions of the construction project, tend to decrease.