I don't have everything worked out, so take my comments for what they're worth. Very, very, low cost.
First, your Constitutionally protected rights are still in full effect. They, the government, rely on everybody being willfully ignorant, and most are. Second, you likely signed agreements with your local government in the form of a Driver's license and car registration (co-ownership). Voiding these contracts (by not renewing) is something I'm still working on, so I don't have a precise answer for how to handle yourself.
You have a first amendment protection of Liberty, the right to *travel*. Any stop by a cop is an infringement on this right. But, you should ask if the cop if he has a victim with damages and a complaint. W/o aforementioned details his stop is *unlawful*.
Do not identify yourself. You do not need to show a "Driver's" license as you're traveling and not the Driver of a commercial vehicle engaged in commerce.
Further, you have the right to be secure in your persons (fourth amendment). Inform said cop, if necessary, they won't be searching you or your property without a warrant signed by a judge or magistrate.
Also, they may not deprive you of your property without due process, fifth amendment. You may ask the cop if he's the judge, jury, and executioner.
Finally, inquire with the cop if he's taken an oath to uphold the Constitution, the supreme law of the land (there is nothing higher).
Bid him, good day.
On a side note:
I'm contemplating, prior to putting a rights assertion plan together, the use of audio/video recording with real time feed to a server somewhere on the 'net. At a minimum, a wireless hard drive mounted in a secure location. I am also a proponent of building a well thought out plan whereby liberty folks could consolidate into a small geographically defensebable community (something similar to FSP) and asserting our rights together, en masse. No birth certificates, no SSN, no Driver's licenses, no business licenses...just people free to contract within the community or externally to Corporations still residing in the United States jurisdiction.