Rest area is a space providing opportunities to use a restroom, refuel, reduce fatigue and receive mechanical maintenance services. In Korea, entering rate to rest area from mainline traffic and duration time in rest area are the key variables in the determination of size of rest area. However, there are many controversies because of inconsistency of those variables between rest areas. Moreover, cases that parking space of newly opened rest area are heavily congested which led to an early expansion are also reported frequently. Review on studies related to design variables for the size of rest area shows that they mostly focus on entering rate, the most superficial aspect of driver’s behavior with regression analysis with mainline traffic volume of and geographical condition. Also, studies did not succeed to explain the difference in entering rates of two different rest areas with similar mainline traffic volume. In this research, aggregate methodology has been adopted to overcome prior studies’ limitation. DSRC (Dedicated Short Rage Communication) data collected from RSE (Road Side Equipment) along expressway has been analyzed to construct trip trajectory of each vehicle. From the analysis of each vehicle’s trip trajectory, rest area usage pattern has been found out to be a result of each vehicle’s travel characteristics including departure time, time of the day when passing rest area, and driving duration. And as a result, data-driven analysis methodology was able to be laid out.