CCapFPN: A Context-Augmented Capsule Feature Pyramid Network for Pavement Crack Detection

Periodically monitoring the pavement conditions is of great importance to many intelligent transportation activities. Timely and correctly identifying the distresses or anomalies on pavement surfaces can help to smooth traffic flows and avoid potential threats to pavement securities. In this paper, we develop a novel context-augmented capsule feature pyramid network (CCapFPN) to detect cracks from pavement images. The CCapFPN adopts vectorial capsules to represent high-level, intrinsic, and salient features of cracks. By designing a feature pyramid architecture, the CCapFPN can fuse different levels and different scales of capsule features to provide a high-resolution, semantically strong feature representation for accurate crack detection. To take advantage of the context properties, a context-augmented module is embedded into each stage of the CCapFPN to rapidly enlarge the receptive field. The CCapFPN performs effectively and efficiently in processing pavement images of diverse conditions and detecting cracks of different topologies. Quantitative evaluations show that an overall performance with a precision, a recall, and an F-score of 0.9200, 0.9149, and 0.9174, respectively, were achieved on the test datasets. Comparative studies with some existing deep learning and edge based crack detection methods also confirm the superior performance of the CCapFPN in crack detection tasks.