In highway engineering, performance, quantity and status of machines available for projects have direct impact on projects time. For instance, the status of machines, such as working or in trouble, have great influence on the activity execution. Therefore, while scheduling projects, managers always increase spare machines or prolong the activity time to avoid delaying projects time when some of the machines are in trouble in construction site. However, how many are the spare machines and how long are the prolonged activity time, which are estimated subjectively by managers. This subjective estimation has been criticized for systematically overestimating or underestimating quantity of the machines and the activity time. In the paper, a model is proposed to simulate the status of the machines in construction site, and then to evaluate the schedule feasibility considering the performance, quantity and statues of the machines involved.