Dial back the paranoia a bit, ok.
This is not "big brother." This is, however, part of a long term set of projects to study the entire 14th St. Bridge system, which, as someone who lives within site of the bridges can tell you, is long overdue.
As for your consent, well, if you are diving your car in public then there is no expectation of privacy and hence no consent is needed. The police (or in this case the big bad Department of Transportation) have just as much right to observe things that happen in public as you do.