When it comes to lighting, for me there are basically two rules:
1. Have enough light for both vision and visibility
Bikes need two types of lighting: vision lighting (the lights you need to see with) and visibility lighting (the lights that help other road users see you). So obviously for the former brighter is (usually) better while for the latter eye-catching is the key (this generally means flashing).
2. Respect others' night vision
The best way to cause a head-on collision on a dark trail is to dazzle an oncoming rider or pedestrian, destroying their night vision. Avoiding this nasty behaviour is simple manners really—and self-preservation.
Everything else is detail
That's all you really need to know, but here are a few other points that I've learned over the years:
Flashing lights are great: I have two at the rear and one at the front. But they belong on the road, not on dark off-road trails. The sole purpose of flashing lights is road visibility—making you stand out against a 'noisy' background of other lights and distractions—something that's not necessary on a dark trail. On a path I know others can see me perfectly well with my static lights, so I set the flashers to static light.
Even on the road, I'll turn flashing lights to static whenever I'm riding in a group with other riders. (If you're in a bunch, you'll probably be told in uncertain terms what you can do with your flashing tail light.)
Responsible use of helmet lights
I've been criticised for advocating helmet lights before, and I'm well aware that some people are not fans and others are in favour. Despite their potential for harm—and some nasty encounters myself—I still think they have a place. If used responsibly, helmet lights improve both vision (allowing you to 'see around corners') and visibility (by providing the ability to 'flash your headlights' at other road users to get their attention).
The key to polite and responsible use of helmet lights is to tilt them down and away when approaching other riders and walkers. However it takes considerable discipline to deliberately look away as people approach. It is human nature to look at people's faces, probably more so in the dark.
The real trouble with a helmet light is that it magnifies the selfishness of the arsehole and the thoughtless incompetence of the fool.
Always enough lighting to get me home, that's what I need. For me, that means (yes, Audaxers…) a minimum of two independent lights at the front and two independent lights at the back.
The rear lights are both visibility lights: superflash style reds. The whites at the front are a visibility flasher and a vision beam light. Either can substitute for the other in the event of a failure. Oh yeah, and I have single LED lights tucked into my helmet—a white at the front and a red at the back.
Replace batteries regularly
Redundancy extends to batteries (if your lights use batteries). It's kind of sad to see someone with a fancy superflash tail light that's feebly flickering because they're trying to squeeze the last ounce of juice from their battery. It's like they're trading their life and health for the price of a new set of batteries—a false economy is ever there was one.
Get serious. Get a battery charger and buy rechargeable batteries. One of the problems with rechargeable batteries is that they tend to disappear into toys, remote controls, cameras, cordless phones, torches, and all the other electronic devices around the house. Be strong. Suck it up and keep buying rechargeable batteries until the background household demand is satisfied and you always have a supply of fully charged batteries for your lights. Then change and recharge on a regular schedule, whether you think they need it or not. I replace batteries weekly for regular commuting. Your mileage may vary.
Intrigue and uncertainty
Maybe it's not critical, but I like to make it difficult to be mistaken for something else on the road—I want my bike to be seen as a bike. At the same time, when drivers see me at night I want them to have what David Engwicht might refer to as a moment of intrigue and uncertainty: to take an extra look and maybe ask themselves "What on earth is that?" I'd far rather that than have drivers respond to my presence on 'auto-pilot' (which in practice is the same as being ignored). And people tend to do that if they think they recognise another vehicle from the shape and style of its lights. An irregular pattern and shape of lights is intriguing, and therefore more likely to capture attention.
Flashing lights scream "bike" but (as was rightly pointed out in a recent episode of Yarra BUG Radio) it's almost impossible to judge the speed and distance of a flashing light. So a combination of both is very helpful. And an asymmetrical-pattern of both shape and flash/static lights helps to create intrigue and uncertainty, which is a good thing.
Conversely (and almost in contradiction to the previous point), intrigue and uncertainty does not extend to displaying red lights on the front or white lights at the rear. That is not intriguing, that is confusing and just plain stupid. Don't do it.
Reflectives fall into the visibility category and while experienced commentators rightly argue that reflectors alone are inadequate because they only work under specific conditions, they are a great addition to your visibility, especially from the side.
Self-adhesive retro-reflective tape can be applied to any spare surface: seat post, seat stays, chain stays, handlebars, wheel rims (between the spokes if you have rim brakes). The curved tubing of the bike frame is a good surface for reflective tape because it helps to make reflective facets available to a wider angle of incoming lights. Moving parts are good too: I have rings of reflective tape around my cranks, reflective stripes on my helmet and reflective bands for wrist or ankle.
Many commuter and touring varieties of tyres have reflective sidewalls, and I can say from experience that those two big circles reflect very effectively in a car's headlights, again unmistakably a "bike" shape.
I love reflectives. I love the eye-catching way they turn a driver's lights back to them. They are a handy addition to the visibility kit, but I ain't going to rely solely on reflectors.
Expect the worst
Even with all this lighting, I try not to fool myself into believing I'm any safer. I still try to ride like I haven't been seen and expect people to do the wrong thing, that way I'm more likely to be ready to respond when something oddball happens.
Please check out the latest issue of Bicycle Victoria's Ride On magazine for the best recommendations!
Indeed, Ride On magazine usually carries a round-up of current lights each year at around about this time.
I have previously bought the lights that Ride On has recommended with few complaints. Indeed, all but one light in my current lighting rig are listed in the Ride On article.