Highway surface segmentation consists of extracting road surface at pixel-level from the surveillance camera view. Since the intelligent traffic event detection task does not require the detection of off-road scene, the segmentation of highway surface is of great demand. However, it is challenging to accurately extract road surface in real time scenarios. To cope with the above issues, Bi-Unet, a dual stream lightweight network is proposed. Firstly, the dual stream structure enhances segmentation performance on the narrow remote end of the highway and preserves the detailed border information. Then, to perform real-time segmentation, a novel lightweight module (LSM) is introduced to lighten the model and provide higher segmentation accuracy. Moreover, to ensure road segmentation for complex scenes, a Road Attention Network (RAN) module is proposed. Lastly, due to the lack of a suitable benchmark dataset serve for the highway segmentation problem, a new large and high-quality segmentation dataset named Highway-Surface-Free (HSF) is proposed in this paper, which is collected from the perspective of highway surveillance cameras under all-day and all-weather conditions. Compared with the state of arts, the extensive experimental results verify that our proposed Bi-Unet achieves the best overall performance on our proposed HSF dataset.