Mercedes-Benz R-Class 2008 Owners Manual - Manual (Page 337)

336
Controls in detail
Useful features
Infrared reflecting windshield*
1 Infrared transparent areas
Your vehicle is equipped with infrared
reflecting glass, which reduces the amount
of radiated heat entering the vehicle
interior through the windows.
The infrared reflecting glass also prevents
the transmission of signals through the
glass by in-vehicle electronic devices, e.g.
electronic toll collection devices.
To allow the use of these devices in the
vehicle, infrared transparent areas are
placed in the windshield.