Dataset http://www.stat.ucla.edu/~tfwu/papers/parking_lot_release.zip    and  source code (https://github.com/tfwu/AOGDetector)  for papers:

[1] Bo Li, Tianfu Wu* and Song-Chun ZhuIntegrating Context and Occlusion for Car Detection by Hierarchical And-Or Model, ECCV (6) 2014: 652-667 (oral)

[2] Tianfu Wu† , Bo Li† and Song-Chun Zhu, Learning And-Or Models to Represent Context and Occlusion for Car Detection and Viewpoint Estimation, IEEE Trans. on Pattern Analysis and Machine Intelligence (TPAMI, Accepted), arXiv 1501.07359