If you're cheap you could always try a gopro sticker off evilbay. Stick it on your rear bumper and see how it works.
Body by Nautilus, brain by Mattel
Good grief, I think there's enough hot air in this thread we could turn it into a balloon and take flight.
To OP, I'd suggest a route with less traffic, if possible. I live in the greater Providence area of RI, which is not always bike friendly. I used to take the most direct, and most dangerous, route to work. Now, I take a few back roads and even take a bike trail for a few miles. Have you noticed you run into dangerous drivers on the same road/area? I can't help but think of the phrase "trying the same thing over and over again with the expectation of a different result is a sign of insanity". You say you've been dealing with this for 2 years! There's got to be a solution! A different route may help.
As for the GoPro, I've read that the later models have a bad battery life. They're better in terms of video quality, but the Hero4 battery lasts roughly 20-30 minutes, based on Amazon reviews. If your trip is less than that, the Hero4 might be a good fit. For what it is worth, I know the early Hero models are still decent cameras and have a better battery life.
This thread was 2 years old, why the F did @RoboChrist bring it back up??
But FWIW my Hero4 Silver battery lasts about 1:30 to 1:45 recording in 1080p 60 FPS mode. Plenty long enough for my one-way 15.5 mile commute. I have 3 batteries for it, and rotate them out (bring spare battery and memory card in my trunk bag for the trip home).
2011 Felt Z85 105 | Ultegra | KMC | Selle Italia | Vuelta | Topeak
2006 Marin Pine Mountain custom build Dutch-styled, disc-brake'd steel utility hauler
I just bought a Contour Roam3. I had an original Roam and sold it because of the inability to erase the card or change settings in the field and no loop recording.
Since then they've added a format button and a switch to allow you to choose in the field between two user-defined settings. Also the battery life is 3.5 hours, which is at the bottom end of acceptable for me (my commute starting late summer will go from 13 to 26 miles). And they're $99, and the Contour form factor is great for a helmet.
Cameras I've had in the past and sold, several generic Chinese cams, a GoPro Hero2 White, a Sony original ActionCam, several keychain cameras, a Contour Roam, an SVC-200, an RD32-II, and probably some that I've forgotten. Some are still lying around here somewhere. On the rear I have a Fly6 which is the ONLY camera that I've owned that I really have no complaints about at all.
Work: the 8 hours that separates bike rides.