not considered.

In the meantime, thorough surveys on pedestrian detection have been conducted by e.g. [@EnzGav:tpami09; @DolEtAl:tpami12]. The evaluations in [@DolEtAl:tpami12] is more recent, where the pedestrian instances are geometrically grouped into three scales: near, medium, and far. [@DolEtAl:tpami12] proceeds to present their Caltech dataset as a reasonable sample of typical pedestrian images, where the data is collected by adopting a standard vehicle-mounted camera. In this influential dataset, near-scale corresponds to a pedestrian object of 80 or more pixels in height, medium-scale is for a pedestrian object between 30-80 pixels, and far-scale is for 30 pixels or less. In terms of physical distance between the pedestrian instance and the camera, these three scales (i.e. near, medium, far) roughly correspond to a typical pedestrian with a distance below 20, 20-60, and over 60 meters, respectively. As noted in [@DolEtAl:tpami12], the medium- and far-scale instances comprises the majority (84% in this case) of the pedestrian population in a typical imaging setting, and human observers have no trouble in detecting most of them. In contrast, existing pedestrian detection methods perform rather poorly in the presence of these instances, despite the fact that the same detectors work very well with those near-scale instances. Take 