Does "Cool Cars" Rule Block Wireless Signal? Cali Says No

A new rule in California meant to help keep vehicles cool in the sun (and thus cut the need for fuel-chugging air conditioners) could interfere slightly with signal reception for GPS devices, but probably won’t block most mobile phone signals. Those are some of the findings in a report released this month by the California Air Resources Board, which dug into the matter after gadget and car makers protested that metallic glazing required under the so-called Cool Cars initiative would block, or at least degrade, in-car wireless reception.

Set to phase in starting with the 2012 model year, the Cool Cars regulation comes as part of California’s Global Warming Solutions Act (AB 32), which mandates a drop in greenhouse gas emissions for the state to 1990 levels by 2020. Noting that “reflective windows are known to attenuate electromagnetic waves,” ARB explains in its report that it researched ways to work around this problem and decided to allow a small portion to be removed from the glaze (a “deletion” window, pictured at left) where signals would be able to come through unhindered. Nice try, but not enough, said Garmin International, Toyota, Nissan and other companies in recent months.

ARB’s report on electromagnetic interference due to the required glazing looks at how GPS navigation units, cell phones and GPS ankle bracelets worn by some parolees performed in a small test (just a handful of vehicles in a limited area). The 30-page document includes three key points — GPS devices are the most likely among the devices to see a dent in their signal strength, while cell phones in urban areas with strong reception will be just fine, and parolees don’t have to worry about setting off false off-the-grid alarms for their monitoring officer when they drive. Or, as ARB put it:

  • “GPS navigation data revealed that GPS devices are impacted by reflective glazing, but that navigation accuracy was improved by placing the device or an external antenna in the deletion window.”
  • “Cell phone calls were not impacted in any way by the presence of reflective glazing. However, the cell phone test only evaluated the ability to make a phone call in an urban environment where cell phone signals are generally strong.”
  • “In total, these results indicate that there are no effects of reflective glazing, and thus the Cool Cars regulation, on GPS monitoring ankle bracelets or cell phone usage in an urban environment.”

But GPS devotees of California, take heart — you probably won’t be sent back to the dark ages of paper roadmaps anytime soon. Automakers also have an option to use other technologies besides the metallic glazing (ARB suggests solar reflective paints, passive or active ventilation systems, solar reflective or thermo-regulating materials, and vehicle insulation) if they can prevent the same amount of heat gain.

The ARB test found that the first phase of the Cool Cars initiative — which calls for glazing only on windshields (for prevention of 45 percent of solar heat gain) — leaves plenty of untreated window space for signals to come through. By 2016, when the second phase calling for treatments of side, rear and rooftop windows begins (for prevention of 60 percent solar heat gain), we expect something will give: California will backpedal on the rule (unlikely, given the state’s stance so far) or automakers and device makers will figure out a way to make it work in order to compete in the California market for location-based services (by 2013, the global market for these services is forecast to reach $75 billion). On balance, according to ARB statistics cited in the Detroit News, it would mean avoiding 700,000 metric tons of carbon dioxide from vehicle emissions by 2020.

Photo credit California ARB