Studio's motion tracking leaves a lot to be desired. I spent a considerable amount of time adjusting trackers to focus on the license plate. It was blurred the way I wanted but then the mask turned black and is unstable. See link below.

The latest version of a competing editor has a vastly superior motion tracker if anybody needs the feature.

 I have it working on a clip from the sample movie but again it required lots of tracker tweaking.  

https://youtu.be/IzUTIRTKRB0

You know it. Standard modus operandi here.

It really got tricky when I was waving the steering column in front of it. Even with two trackers. 

If not for the object being obscured then not the "car" colored blank title blocker method would have worked.

Of course 30 minutes time to setup and shoot the segment again minus the car was too easy for my nonsenseabilities.  

Plus I had sworn I had no need whatsoever for the latest iteration of that NLE and ended up netting a couple valuable bonus "prizes" for waiting them out a month or two. Sweet!