This article by wjhl.com talks about the crime-solving benefits provided by cameras installed in traffic intersections in Johnson City, Tennessee.

I have seen these same kinds of cameras also in every intersection ("every" as in everyone I drove past) in Massachusetts and Florida. Apparently there is quite a lot of monitoring going around.


These cameras are not used for traffic lights at least according to the article referenced above (which indicates that the images from the cameras are routed to some kind of monitoring center somewhere).

This question was prompted by the consideration that usually any form of tracking of citizens (and esp. of the type that invades the privacy of the citizens within their own property, although I guess being inside a car does not qualify) is supported by some law passed by Congress.

Thus the question I wanted to ask is, what law(s) has Congress passed that has allowed the installation of these cameras?

  • 9
    Two big assumptions here: A) that there is a need of a law to be passed in order to install the cameras in public spaces and B) in case of A, that such a law comes from Congress and not from State (or lower) levels.
    – SJuan76
    Commented Nov 23, 2017 at 19:38
  • 3
    @jamesqf Pretty sure light timing (when its installed) is based on inductive sensors under the road, the cameras are for catching people who run reds. Speed cameras are usually based on the side of the road in their own enclosures or (occasionally) vehicles. Only on certain barrier free toll roads do the cameras actively catch all plates to process payments for the toll (they could theoretically also catch people going over the speed limit via basic arithmetic, but I don't think anyone bothers).
    – Teleka
    Commented Nov 24, 2017 at 1:12
  • 1
    @jamesqf In MD cameras can be used to issue citations, and there are still plenty of inductive sensors around; I know the DC metro area has them, as does parts of Indiana at least. It's true that they don't work that well (dragging a bicycle across the payment to maybe trip a switch is pretty ridiculous), but they're definitely pretty widely used. These sorts of things probably varies a lot based on location. I don't see what your front plates comment have to do with anything though, both red light and speed cameras are designed to capture from the back.
    – Teleka
    Commented Nov 24, 2017 at 4:38
  • 2
    What law allows you to eat spaghetti on Tuesdays? Point being we don't pass laws for what you are allowed to do as much as not allowed to do.
    – user1530
    Commented Nov 24, 2017 at 6:53
  • 2
    @blip, regarding your question "What law allows you to eat spaghetti on Tuesdays?", it is and was obvious that when it comes to the citizens, the laws are written from the perspective of what is not allowed. However these cameras are of course not installed by citizens but by local or state governments. When it comes to what the governments are allowed to do, esp. in cases that relate to invading the privacy of their citizens, there are generally laws that regulate and either allow or deny that.
    – alec
    Commented Nov 24, 2017 at 16:48

1 Answer 1


Short answer: None.

Congress does not enforce traffic laws. That's a state's power. Within states, they may authorize the use and set the rules, but ultimately it's up to the local level police to do these (State Police are typically used on limited access highways and Interstates, which don't typically have intersections). As it was mentioned in the notes, I live in Maryland (MD) and can tell you that the use of cameras is very much contentious. Most citizens hate them and they tend to exist in more prevalence in the less rural parts of the state and between Baltimore City and Washington D.C. (inclusive).

Under MD law, you do have to provide proof that you were not driving the car at the time the picture was taken. This may seem like a violation of "Innocent until proven guilty" but I've heard of judges who have ruled against cases that use it. The fine is also set at $40 dollars, which is supposed to be enough to give a little hurt to the driver but not enough that they would want to contest it in court or appeal following a ruling (most judges will waive it if you bother to show up in court.). The fact that they don't assign points to a license so repeat offenders will be unable to legally drive has led to accusations that the whole system is a money grab.

  • The use of cameras for enforcement being a money grab is why some states (Nevada, for one) have made that illegal. But we still have the cameras as traffic control measures. (And other cameras that are mostly for looking at road conditions: e.g. if I look here nvroads.com I can see road & snow conditions at my usual cross-country skiing place.)
    – jamesqf
    Commented Nov 24, 2017 at 18:12
  • One quibble: In DC, the territories, and on federal property, Congress can write laws about red light cameras. I don't think they've done so, but they can if they want to.
    – cpast
    Commented Nov 25, 2017 at 17:33
  • @cpast: As a general rule, the U.S. Territories have the same powers as would afford a State, so they do have the same rights of self-government and are effectively a state without the ability to elect the President. Congress gave DC the right of "Home Rule" to manage the more day to day aspects of the city, so their Mayor and City Council act under that authority. In D.C.'s case, they could in theory, but to I'm pretty sure they want to keep that at the more local level.
    – hszmv
    Commented Nov 27, 2017 at 17:05
  • @hszmv While territories have self-government, Congress retains full authority to legislate for them (including altering or abolishing their government institutions at will) just as they do for DC.
    – cpast
    Commented Nov 27, 2017 at 18:37

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .