LG Display has produced the first transparent OLEDs that are large enough to be used as subway train windows. 

At first, the translucent displays will be used on trains in the Chinese cities of Beijing and Shenzhen, with LG Display the first company to introduce 55-inch transparent OLEDs for subway windows. There is no information about resolution or luminance of the displays, just like there is no data about their expected lifespan or power consumption. Based on the image provided by LG, we are talking about a fairly high-res display with a decent brightness, and good viewing angles.  

Source Article