Iím currently building Railcars that have curved windscreens. I had a couple of unsuccessful goes at building these before I hit on this method.
I cut the clear plastic longer that I needed and clamped it to the inside of a sweet tin. Then heat was applied using a hairdryer and it resulted in forming the correct shape.
I had left the protective film on the windscreen and it is wrongly showing up in the photo as if the plastic had melted.
The end result.