[Reason077]

It’s not an issue with dirt on the windows, but rather etching/clouding of the window glass which makes it appear dirty.

It’s certainly not unique to NJ: it happens on a lot of older trains in Europe, but I’ve never seen it so bad as in the NJ photos.

I guess something about the coating they use on the glass (to improve safety, insulation, etc) makes it vulnerable to clouding and scratching over time. Climate, air pollution, and/or cleaning techniques used over the years may have contributed to the issue?

[mannykannot]

From the end of the story:

"Metro-North Railroad and NJ Transit use a single pane of polycarbonate glazing almost a half inch thick, according to the Federal Railroad Administration.

"NJ Transit isn’t alone in this problem.

"“The south side of the (Long Island Rail Road) M-7 fleet of 830 cars is also opaque,” Versaggi said."

LIRR trains run predominately east-west routes, and (I assume from this comment) apparently do not turn round at the termini.

It does not quite say that the affected LIRR trains also use polycarbonate windows, but it seems likely that they do, and that the cause of the opacity is sunlight damage to polycarbonate, or some plasticizer or other minor component of the windows. It is well-known that polycarbonates absorbs UV, and that energy has to go somewhere...

[vikingerik]

Right, LIRR trains don't turn around at any terminus, so the same side is always the south side. I think the only balloon loop in the system capable of turning a train is at Sunnyside Yard, but that's a maintenance/storage facility and not really a terminus; it turns Amtrak trains but never LIRR. There is a wye capable of turning an engine but not a full-length train at the ends of the Montauk and Port Jefferson branches, and perhaps others.

[scherlock]

The windows are not glass, they are 1/2" polycarbonate, per the article, which is easily scratched and susceptible to UV damage. That is the problem. They could likely be polished but then they need to retest the windows for safety compliance.

[kevin_thibedeau]

The older single level Comet cars don't have this problem nor does the light rail. Seems the solution is to replace with a longer lasting window material which is already known to work.

[analog31]

That material is glass. However... replacing panes with glass isn't a straight swap of one material for another. The glass has to be protected around the edges, it can't be drilled for screw holes, etc. The re-design involves not just the window material but the window system.