[King-Aaron]

To expand on your answer, judging by the IR led's in the 'floodlight' arrangements on top, I'd say 100% that they're scanning plates, and it's highly likely they're doing face scans too(i.e. http://iomniscient.com/) and other imaging.. For instance in Australia they sometimes check for people not wearing seat belts with similar camera arrangements. I'd also bet that they take speed readings.

They likely house a level of chemical-sniffing technology too, like police cars can be equipped with (http://www.inficon.com/). These sniffers would likely be actively looking at emission levels etc (being near tunnels would provide a reason for that), however can also detect explosives etc.

[tobtoh]

> For instance in Australia they sometimes check for people not wearing seat belts with similar camera arrangements.

I live/drive in Australia and I've never heard of such a thing - neither location or anyone fined by this method. Do you have an example location where this is in place? Or an article describing it?

[King-Aaron]

Yeah as the comment below notes, I should have been clearer. They manually check, however I can't see it as too much of a stretch that an operator might check the feeds every now and then for such a thing. I know in the Northbridge Tunnel (Perth) they don't send fines for speeding infringements, yet if you are seen driving dangerously through the tunnel they'll get you for everything they can positively identify as illegal if they want to follow you up - i.e. in the event of an accident etc.

Source: My brother is an officer and have discussed with him about what they do and don't monitor.

Edit: old article link as the other commenter seems to have removed theirs http://www.adelaidenow.com.au/news/south-australia/sa-police...