The view out of motor vehicles is obstructed by the body contour, columns, hood, mirrors and wiper. The figure illustrates the field of view through the windshield and the obstruction of sight by the interior mirror.
Although the maximum possible angles of vision in the upward and the downward directions amount to 45° and 65° respectively, by virtue of the eye movement, the actual available direct field of view is limited by the dimension of the windshield. The tangents drawn from the opening onto the eye ellipse indicate the boundary for the direct field of view for approximately 90% of the eye positions. The area within which sight obstruction occurs for these eye positions is characterised by the tangents drawn from these obstructions (a point nearest to the eye) to the eye ellipses and the maximum covering angle for 95% of the eye positions is included within this beam of sight.