What type of glass is generally used for the outer windows of a railcar?

The correct choice reflects the material commonly used for the outer windows of railcars, which is typically tempered glass or Lexan. These materials are specifically chosen for their heightened strength and impact resistance, which are critical for safety and durability in rail applications.

Tempered glass is manufactured through a process of extreme heating and rapid cooling, making it much tougher than regular glass. When it breaks, it shatters into small, blunt pieces rather than sharp shards, reducing the risk of injury. Lexan, a type of polycarbonate, offers similar advantages with additional properties such as lightweight design and excellent optical clarity.

In contrast, standard glass and non-tempered glass lack the necessary strength and safety features required for high-stress environments like railcars. Such materials could present significant safety hazards if shattered during operation. Plastic, while lightweight, may not provide the same level of impact resistance and could be less stable under varying temperatures and conditions. Therefore, the choice of tempered glass or Lexan aligns with industry standards for passenger and crew safety in rail transport.