The object tracking benchmark consists of 60 training sequences and 40 testing sequences. Only the vehicles outside the ignoring region are annotated and evaluated in our benchmark. For the benchmark annotation, a group of volunteers manually annotate the 2D bounding boxes in every 5 frames. Annotations in other frames are produced using linear interpolation. All bounding boxes are manually verified, and inaccurate bounding boxes are manually adjusted. In summary, we annotated 8250 vehicles in the benchmark, including 5936 vehicles (i.e., "car": 5177, "bus": 106, "van": 610, "others": 43) in the DETRAC-train set and 2314 vehicles (i.e., "car": 1961, "bus": 199, "van": 123, "others": 31) in the DETRAC-test set. We propose a new evaluation protocol for object tracking and MOT system evaluation. The proposed DETRAC evaluation protocol considers object detection and object tracking in tandem. Specifically, we advocate to evaluate MOT performance using the joint precision vs. recall vs. multi-object tracking performance curves (refer to arXiv paper). Out development kit provides details about the data format as well as utility functions for reading and writing the annotation files.