Evaluation of Alternative Pre-trained Convolutional Neural Networks for Winter Road Surface Condition Monitoring

Real-time winter road surface condition (RSC) monitoring is of critical importance for both winter road maintenance operators and the travelling public. Accurate and timely RSC information during snow events can help maintenance operators to deliver better maintenance services, such as plowing and salting, for reduced costs and salt usage and improved level of service. With this information, the traveling public can make more informed decisions on whether or not to travel, where to go, and which highways to drive on. In our previous effort we have shown the potential of applying a pre-trained convolutional neural network (CNN) for automatically detecting winter road surface conditions based on images from fixed traffic/weather cameras or in-vehicle devices. This paper focuses on comparing the performance of four most successful CNN models available from the leaders of this technology, namely, VGG16 (Oxford University), ResNet50 (Microsoft), Inception-V3 (Google) and Xception (Google), for solving the RSC classification problem. The models were first customized with additional fully-connected layers of neurons for learning the specific features of the RSC images. The extended models were then trained with a low learning rate for fine-tuning by using a small set of RSC images. The models were tested using a hold-out set of images from cameras installed at different locations, showing highly encouraging results.