The time and range of the system depend on the type of RTLS scheme that is implemented, the radio TX power, the sampling frequency, the environment and the way the anchors are set up. We have an AN on the Max Range in DW1000 Systems that may be of help.
I’m assuming you are using PANS 2.0 (the system programmed by default on the DWM1001 devices).This system uses TWR (To Way Ranging) between tags and anchors in order to calculate an absolute position of the tag. One thing this system might be able to do for you is already tell you when a tag is in range of one anchor. This would’t give a full absolute position, but it would allow to quickly know a car entered, or is close to, the ranging “bubble”. In order for the absolute position to be calculated the tag needs to be found by at least 3 anchors. On top of that some calculation time is required.
I don’t know if we have any data on how fast this system can locate new tags, since this really depends a lot on the setup and the environment. At high enough sampling rates and in a properly configured environment the time to locate a tag is fairly short making it suitable for most RTLS use-cases. I suggest you test this for yourself and validate the speed for your use-case. While we can offer some generic information, we will not be able to provide an accurate answer.