dark windshields

[Anonymous]

Gentlemen railfans;
One thing that has been overlooked about the windshields, particularly inthe northern climates, is that these windshields are electicly heated for de-icing purposes. THis makes the w/s darker than normal. The heating material used id either tin oxide fired-onto the glass or a gold vacuum deposited on a substrate and laminated into the windshield. Both coatings are electrically conductive and thus exerts a resistance to the flow of currrent. Typically 72 volt source is used to power the w/s. Note the power bus bars along the top and bottom of the windshield for power application.
Now as to the small arms protection, these windshields were tested using bricks lobbed at the w/s at 60 mph with the results of having no penetration of the brick. Now this may extended to assume that this will also protect the crewmen from small arms fire. In some cases it will; however, is the angle of incidense is small enough, there will be some penetration. On the other hand, if the angle of incidence is large enough, then the projectile will be deflectd with little damage or penetration.
The above information was due to FRA requirements from the 70's and 80's. However, the design of the window has not changed appreciably since that time.
Remember also that window tinting is an external treatment for reflecting IR radiation from the w/s. Some treatments are internal and is a metalic type of coating.