1. Department of Metropolitan and Urban Transportation Research, Korea Transport Institute, 2311, Daewha-dong, Ilsanseo-gu, Goyang-si, Gyeonggi-do, 411-701, South Korea.
2. Department of Transportation and Logistics, Chonnam National University, San 96-1, Dundeok-dong, Yosu, 550-749, Chonnam, South Korea.