Check out the GitUp or SJCam cameras, I have both. You don't need the latest model to catch the number plate on cars, so long as the resolution and stablisation is sufficient. You can save by buying a model from 1 or 2 years ago. They can be purchased cheaply from
ebay or aliexpress. Watch out for fakes, only buy from sellers with good ratings. They are
GoPro like cams. HD recording without the HD price tags. I only use a front cam with a quick release system mounted on the underside of my handle bars, I've so far picked up many close passes and had one dealt with by police, I can recommend them highly and they don't cost the earth. They definitely don't make you safer. And there's always the danger you are more likely to be drawn into confrontation if you are tempted to catch them on camera. They can also provoke additional violence and/or irrational anger when road ragers know they are being filmed. Hence hanging mine inverted under the bars, even fellow cyclists don't notice it. The GitUp allows you to turn off the blinky red lights too.
My only gripe with them is that battery tech needs to improve significantly, until then I have to charge the Li-ion battery after every ride on my 11 mile commute. A more expensive camera won't solve this problem however, you can take battery banks with you if you are prepared to do some DIY modifying waterproofed cases and find a way to store the external battery safely in the event of a downpour.