ARB Report Finds Reflective Glazing to Meet Cool Cars Regulation Will Not Impact Certain Portable Devices
The California Air Resources Board (ARB) has published a report evaluating the potential electromagnetic interference on certain portable devices such as cell phones, global positioning systems (GPS) and ankle monitoring bracelets due to automotive reflective glazing as required under the “Cool Car” regulation . (Earlier post.)
The results indicate that there are no effects from reflective glazing, and thus the Cool Cars regulation, on monitoring ankle bracelets or cell phone usage in an urban environment. Effects on GPS navigation units were observed, but these were completely eliminated by placing the device or an external antenna within a “deletion window”—a relatively small section of the windshield manufactured without the reflective material.
Background. The Cool Cars regulation, which aims to reduce the need for air conditioning by reducing the heat gain of vehicles parked in the sun, was an early action item under AB 32 and adopted by the Air Resources Board (ARB) in June 2009. When fully implemented the regulation will require a 60% reduction in heat absorption through vehicle windows.
Cool Cars specifies that vehicle windows must meet certain standards for heat transmission. Based on these requirements, ARB expects reflective glazing to be installed on windshields in 2012 and on all windows in 2016, unless automobile manufacturers decide to use an alternate performance option for 2016 and beyond.
Reflective windows are known to attenuate electromagnetic waves, and in preparing the rule, ARB staff had researched what methods could be used to mitigate signal attenuation. Staff determined that a portion of the reflective material could be removed in order to facilitate operation of electronic devices.
However, concerns were still raised that devices such as global positioning system (GPS) monitoring ankle bracelets, cell phones, and GPS navigation devices will not operate as intended in vehicles with reflective glazing. ARB initiated a test program to evaluate the potential effect on these devices.
Testing. ARB tested three types of devices: GPS monitoring and ankle bracelets using both GPS and cell phone signals; GPS navigation devices, evaluating time to first fix (TTFF) and navigation/tracking ability; and cell phones, using both CDMA and GSM networks.
ARB tested manufacturer-installed reflective windows in vehicles from Mercedes-Benz, BMW and GM. Overall, staff found that:
Reflective Glazing had no effect on monitoring ankle bracelets or cell phones.
GPS navigation devices are the most affected, with the largest effect observed in the TTFF with all around reflective glazing.
Effects on GPS navigation devices were completely mitigated by use of deletion window (about 4% of the window area in the test), when placing the device in the window or placing an external antenna in the window.
ARB said that automakers will be required to indicate both with words and graphically in the owner's manual the location of the deletion windows.
Other devices such as transponders and garage door openers were not tested. ARB staff said it expected those devices to behave similarly to the GPS devices in that effectiveness will be enhanced by placement of the device in the deletion windows.
Evaluation of Electromagnetic Interference Due to Automotive Reflective Glazing (ARB report, Nov 2009)
Electromagnetic Frequency Interference Test Plan Results (ARB presentation, October 2009)