I. Introduction
Vehicle classification is a key element of the intelligent transportation system and has various applications such as traffic flow statistics, intelligent parking systems, and driver assistance systems [1]. In the past, several researches have been done on the vision-based vehicle classification using support vector machine (SVM) [2] to train classification models. The conventional method is not robust due to unstable feature extraction from illumination change. Because convolutional neural network (CNN) learns itself without the need for people to extract features, it complements drawbacks of the conventional method and has contributed to the rapid development of the image classification [3].