General Road and Highway Discussion

[MacBerry]

Can someone explain why the noise barriers on the new 7/8 overpasses (Westmount, etc.) are transparent (acrylic?) and different from the rest of the barriers along the 7/8?

Is it purely for aesthetics? Safety reasons? Better lighting? To allow for greater solar snow melting in winter? Cheaper? Better sound abatement?

Thanks.

https://www.google.ca/maps/@43.1750619,-...312!8i6656

 Are the acrylic/tempered glass panels shown in the above GOOGLE maps link, tethered in for safety or are  they being warmed in the winter? Look at the top of each panel in the sections over the roadway below? 

Something else?  Just for #Ss&Gs? Burgler alarms?