From FastTrak website it says, "Please note that if not properly mounted, the transponder may not work and may be unlawfully positioned per SEC.77, Section 26708 of the Vehicle Code"

Also this link: https://www.thetollroads.com/violati....do?dest=faq#7

mentions that the CHP is authorized to "cite drivers who fail to properly mount... transponder to windshield"

California's DMV website at: http://www.dmv.ca.gov/pubs/vctop/lov/lovd11.htm

mentions way down at vehicle code 23302(b) that it is an Infraction, for "Failure to display transponder on specified vehicle..."

And lastly: http://www.dmv.ca.gov/pubs/vctop/d11/vc23302.htm

That one specifically says, "...the device shall be located in, or on the vehicle in a location so as to be visible for the purpose of enforcement at all times when the vehicle is located on the vehicular crossing or toll highway."

Hope this helps you. Anything further, you'll have to "google" for yourself.

-Tony

 

Here in the Northeast we've been using EZ Pass for years. The transponders usually come with Velcro on the back. Normal usage in this part of the world is stick it on the windshield just above the rear-view mirror, and below the anti-glare black nubs at the top center.
Works just fine for thousands of people.

 

Same here for California for FastTrak and EZ pass systems. It just seems that we as Californians are averse to putting them on our windshields (and I don't know why that is), myself included. But, since finding out the hard way, my FastTrak is velcroed where it should be.