I commute every day to and from work. I have experienced drivers making left turns in front of me in broad daylight. They don't see you. 99% of the time it wasn't on purpose. To increase my survivability, I have installed a front-facing LED strobing white light purchased from a bicycle shop. 800 lumen is powerful enough to have the light bounce back from any street signs 500 feet away. With this mod, the only driver that will turn in front of me is the jerk who is doing it on purpose. I will not ride without this mod.
To reduce the chance of getting rear-ended, I've installed a red back-facing led strobe light. Again, both of the LED lights were purchased from the bicycle shop.