There is no need to contact the police as LA passed a historic bicycling anti-harassment ordinance in 2011. I live in Oakland, which just passed the same ordinance based on LA (and later Berkeley's) ordinance. If a motorist endangers you, for instance by driving less than 3 feet from any part of your bicycle, you can file a civil case and collect treble actual damages or $1000, whichever is greater.
The more important part is that the violator is responsible for reasonable attorney fees and court costs. This is a *big* deal because this means a bicycle friendly attorney can accept your case easily, with no cost to you.
Better to read the actual ordinance, or do what I do and print it out and keep a copy while riding your bicycle.
(pdf link) https://oakland.legistar.com/View.as...B-E76F0056483C
If you had video to record the license plate, you could have made $104,000 over the past two years! After Oakland passed the anti-harassment bill, I bought a gopro and am waiting to catch my first "grazer". I have been passed by cars closer than 3 feet but I felt the cars were passing slowly and respectfully, which is perfectly fine by me. It's obvious when someone is careless and dangerous and that is the person I want to change behavior with this ordinance.
I already picked out a bicycle friendly attorney and will send him a youtube link when the time comes. He will likely hire a PI ($100) and file a case ($225 for cases under $10k) plus reasonable attorney's fees plus my $1000.