Motor Vehicle Safety Regulations — 111
 0.000873 is the tangent of 3 minutes of arc; and (b) the shortest angular length of the image shall be no less than 9 minutes of arc, measured using the following equation: Y/D ≥ 0,002618 where Y is the length of the image of the cylinder on the reflective surface, D is the distance between the centre point of the driver’s eye position and the centre of the reflective surface, and 0.002618 is the tangent of 9 minutes of arc. (23) For the purposes of subsection (22), a comparison chart, such as the one shown in Figure 2, may be used to measure the angular width and angular length of an image of a cylinder, where (a) the comparison chart is placed in a vertical plane that contains the image to be evaluated; (b) the plane of the comparison chart is perpendicular to the line of sight; (c) the image of the cylinder and the comparison chart are visible through the still or video camera’s viewfinder; (d) a photograph is taken at the driver’s eye position; and (e) the image of the cylinder is larger than the references shown on the comparison chart. (24) Images reflected in each System B mirror shall be located no less than 3 minutes of arc from the edge of the reflective surface, when measured at the driver’s eye position. Testing (25) A System A mirror and a System B mirror shall be tested as follows: (a) cylinders A, B, C, D and E shall be placed at the following locations, as illustrated in Figure 1, with measurements taken from the centre of the cylinder, as viewed from above: (i) cylinder A shall be placed in front of the bus so that its centre passes through the bus’s longitudinal centreline and its top is directly visible through the portion of the windshield wiped by the windshield wipers at the driver’s eye position, (ii) cylinder B shall be placed on the side opposite the driver’s side at a point where the cylinder is entirely visible through the convex mirrors of both System A and System B on that side so that its centre falls in a vertical plane that is 2 m (6.6 feet) to the right of, and perpendicular to, a vertical plane tangent to the bus’s most outboard surface, (iii) cylinder C shall be placed on the driver’s side at a point where the cylinder is entirely visible through the convex mirrors of both System A and System B on that side so that its centre falls in a vertical plane that is 2 m (6.6 feet) to the left of, and perpendicular to, a vertical plane tangent to the bus’s most outboard surface, (iv) cylinder D shall be placed on the side opposite the driver’s side so that its centre falls in the vertical plane that passes through the centreline of the bus’s rear-wheel axle and that is 2 m (6.6 feet) to the right of the bus’s most outboard surface, and (v) cylinder E shall be placed on the driver’s side so that its centre falls in the vertical plane that passes through the centreline of the bus’s rear-wheel axle and that is 2 m (6.6 feet) to the left of the bus’s most outboard surface; (b) every mirror shall be adjusted in accordance with the manufacturer’s recommendations to the driver’s eye position and is not to be moved or readjusted during testing for that eye position but may be readjusted for subsequent tests for different eye positions; (c) a still or video camera shall be positioned so that its image plane is located at the driver’s eye point in such a manner that the reflective surface is visible to the camera through the windows of the bus; (d) for a specific driver’s eye position, the requirements of subsections (16) to (25) shall be satisfied with the still or video camera positioned at either the left or right eye point; (e) the still or video camera shall be supported so as to allow pivoting (i) in the vertical and horizontal planes of its image plane to no greater than the maximum allowable limits of eye rotation specified in SAE Recommended Practice J1050, Describing and Measuring the Driver’s Field of View (August 1994), and (ii) in the horizontal plane of its image plane to no greater than the max