1. A computer implemented method of detecting a vehicle in a video frame, the video frame acquired from a fixed parking occupancy video camera including a field of view associated with a vehicle parking region, the method comprising: a) capturing a video frame from the fixed parking occupancy video camera, the video frame including a ROI (Region of Interest) oriented by an orientation angle relative to an orientation of an image plane associated with the captured video frame, the ROI including one or more parking spaces of the vehicle parking region; b) rotating the ROI by the orientation angle of the ROI; and c) performing a sliding window-based 2-D (Dimensional) space search for a vehicle within the rotated ROI, the sliding window-based 2-D space search extracting one or more features associated with each of a plurality of windows and accessing a classifier to classify each window as including a vehicle or not including a vehicle.