(a) Windows and other openings at the operating station must be of sufficient size and properly located to provide an adequate view for safe navigation in all operating conditions.

(b) Glass or other glazing material used in windows at the operating station must have a light transmission of not less than 70 percent according to Test 2 of American National Standards Institute (ANSI) Z 26.1 “Safety Glazing Materials For Motor Vehicles Operating on Land Highways,” and must comply with Test 15 of ANSI Z 26.1 for Class I Optical Deviation.