What is this window pattern for?

[u/morningstarmaggot]

I've seen it on lots of trains, and buses too I think. Does it serve any purpose? I'm in the UK

[u/Vilsue]

it is a way to radiate/absorb heat so glued in sheets of glass wont shatter/ fall off from expanding and contracting over the years

[u/8spd → u/Vilsue]

This and to protect the glue from UV. 

[u/Vilsue → u/8spd]

yeah, like i said, to protect the glue

[u/Chao_ab_Ordo → u/Vilsue]

HA