Yes, the IP address and user agent string are sent, and the time will be known of course, and I am not complaining about that; it is there, you can log it if wa

Yes, the IP address and user agent string are sent, and the time will be known of course, and I am not complaining about that; it is there, you can log it if wanted (and use it for debugging/statistics/whatever), etc. The User-Agent header should not be misused. A legitimate user may well access it in a lot of different ways, some of which affect the User-Agent header, and some of which affect other stuff. (If you need to determine what file format to use, the Accept header should be used instead when possible. The User-Agent header can still be used as a fall back, I suppose.) In the case of cars, yes you can see the license plates, colours, etc, if you are physically there and recording them on a paper or camera, or using surveillance cameras, although for a somewhat different reason I am against putting surveillance cameras everywhere. Of course I am not stopping you from recording this data, although for analyzing traffic congestion, I do not think the colours of the cars is important (although their size and speed and classificiation (e.g. car, truck, public bus, etc) (and perhaps how much noise it makes, if you want to consider noise pollution) might be; I don't really know much about it, as I do not drive a car; maybe you know better).