49 CFR 223.13: Requirements for cabooses built or rebuilt prior to July 1, 1980.

(a) Cabooses, other than yard cabooses, built or rebuilt prior to July 1, 1980, which are equipped in the forward and rearward end facing glazing locations of the windshield with a glazing material that meets the criteria for either portion of the impact testing required for a Type I test under the provisions of appendix A of this part, will not require the installation of certified glazing in the windshield location except to replace windshield glazing material that is broken or damaged.

(b) Cabooses, other than yard cabooses, built or rebuilt prior to July 1, 1980, which are equipped in all side facing glazing locations with a glazing material that meets the criteria for either portion of the impact testing required for a Type II test under the provisions of appendix A of this part, will not require the installation of certified glazing in the sidefacing glazing locations except to replace sidefacing glazing material that is broken or damaged.

(c) Except for yard cabooses and cabooses equipped as described in paragraphs (a) and (b) of this section, cabooses built or rebuilt prior to July 1, 1980, shall be equipped with certified glazing in all windows.

(d) Except for yard cabooses, each caboose that has a window that is broken or damaged so that the window fails to permit good visibility shall be removed from service until the broken or damaged window is replaced with certified glazing.