I’ve run across a lot of discussions in various bike forums about the best way to be visible at night. Much of it is wrong, or at least off the mark. I can safely say this because I have a phd on the topics of visibility and conspicuity, have studied them for 38 years and have investigated many accidents. Here’s my opinion on the best way for bicyclists to ensure being seen at night.

1. Lights, especially flashing lights. This is obvious and requires no explanation. However, lights alone are not enough. They merely “point sources” of light, whose distance can be hard for a driver to judge. Moreover, they can be difficult to interpret ,especially when there are other lights in the background.

2. Reflective vest. It provides a much bigger surface driver to see and is less likely to be lost in the background. I wouldn’t even remotely consider bicycling at night without one. Don't negate the benefit with by wearing a backpack, unless the backpack is also reflective.

3. Be where you are supposed to be. Driver perception is largely governed by expectation, and drivers have strong expectations about where various road objects will be. Don’t violate those expectations if you expect to be seen. I see routinely encounter bicyclists going through STOP signs and red lights, pedaling on the wrong side of the road, going the wrong way down one way streets, driving off sidewalks, etc. This is very risky.

4. Don’t pedal on roads with speed limits above about 40-50 mph. At such speeds, the closing rate is high and the time to overtake is short. Car headlamps just don’t put out enough light for a driver to reliably see and to respond in time. Further, drivers don’t expect to encounter bicycles on such higher speed roads. If you must bike on such roads, stay on the shoulder, even if the ride bumpier.

5. Don’t rely on drivers to see you. One consistent research finding is that pedestrians and bicyclists vastly overestimate their visibility to drivers. Pedestrians and bicyclists see the big bright car headlamps and unconscious believe that they must be as visible to the driver as the car is to them. They aren’t.

Lastly, if you haven't done any other these things and never been in an accident, don't think that you are immune. It just takes the right (or should I say wrong) confluence of events. You have been lucky and never have the confluence happened, but that doesn't mean that it won't in the future. Smart people play the odds. These suggestions improve your odds.
Regards,

Marc Green, author Forensic Vision: With Applications To Highway Safety.