First and foremost, I’m convinced that running a GOOD tail light during daylight hours is a great idea. Yeah, yeah… yet another dorky thing to the fashion conscious cyclists. Get over it: to most of the non-cycling world (that would be about 95% of the people in cars who actually see you cycling), if you ride a bike on the road you ain’t cool anyway, no matter how fast and fit you are or how blinged-out your bike is.
Now that that’s settled, let me point out that just having a tail light on your bike doesn’t mean it will provide you with the visibility you intend. There’s a bit more to it than that, in much the same way as getting the expected protection value from wearing a helmet. Let’s face it, we’ve all seen people wearing helmets that aren’t fitted correctly, with loose straps, or that should have been replaced years ago: net result is that they may or may not protect someone’s head if they should have a fall or collision. I call these placebo helmets…
Tail lights are no different. If the light doesn’t actually make you stand out and get the attention of motorists far enough in advance, then it’s just decoration. To be effective in daylight hours, you need a GOOD tail light, it also has to be positioned and aimed correctly and have ample juice in its batteries.
Here’s the deal, ever since seeing our first DiNotte 140R taillight on the back of Bob & Jan Thompson’s tandem during the 2008 Southern Tandem Rally in Bowling Green, Kentucky, I’ve always taken note of how well (or not so well) other tail lights do at making a bike stand out in day time riding conditions. Honestly, there are only about 1 out of 20 tail lightsI see that are getting the job done. Some of the lights are good products like the Planet Bike SuperFlash, the Cateye TL-LD1100 and TL-LD600. Of course, the DiNotte tail lights always standout light a beacon on a hill a mile away… really, they do.
While this isn’t the best quality video, it does give you a sense the directional nature of LED tail lights and how quickly the intensity falls-off as the direct line-of-sight into the LEDs shifts up, down, right or in this example left. Note that the video image distorts the brightest light into an almost light-red to white light which is what you’re seeing when the video starts with the five different tail lights lined up and flashing.
So, the point is, even some of the better models of tail lights become less than effective if they’re not positioned and aimed correctly. This is because LED-based lights are very much directional, which is to say the LEDs are only at their brightest when they are looked at straight-on. Therefore, if an LED tail light is pointed a little up or down instead of straight back it looses a significant amount of its intensity and range. This is one of the reasons I really don’t favor lights that are attached to the back of helmets, clothing or saddle bags and the like as they tend to be pointed in all the wrong directions, instead of back towards on-coming traffic and motorists. Therefore, if you’re installing a tail light on your bicycle, make sure you take the time to select a light that can be mounted where it can be positioned to point straight back with the LED light path parallel to the ground (excluding DiNotte and other super-bright lights that should be pointed slightly down). And before deciding that you’ve got it positioned correctly, prop your bike up with the light on and move back 100′ to see if you need to fine tune the aim for maximum intensity and range. Again, if the light doesn’t make you stand out to motorists well before they are on top of you, they aren’t of much value.
The other thing that seems to kill the effectiveness of tail lights for day time use is weak batteries. Again, if you have a Planet Bike SuperFlash, but the batteries are only able to generate 1/2 of the light’s intended output, the light becomes of little value in grabbing the attention of motorists. This is why having a light that is powered by a rechargeable power source or simply rechargeable AA batteries that are easy to change is something else to think about when buying a tail light. After all, if the batteries are expensive or hard to replace, chances are you’ll either not use the light all that much or if you do, you’ll run it with low batteries from time to time, and in either scenario you’re not getting the value that the light was intended to provide in terms of increased visibility and safety.
We change batteries a lot. Like every time we ride by rotating 3-sets of rechargeable AA batteries. This allows us to always start our rides with fresh or nearly fresh batteries. In fact, the constant changing of batteries caused a fatigue crack in the 4 – AA battery carrier for our DiNotte 140L tail light. Fortunately, DiNotte used a very common 4-battery carrier that you can find at Radio Shack stores for about $2.20/each. We’ve been using the same 12 AA rechargeable batteries for nearly 2-years now; very efficient, cost effective and a little easier on the environment.
Anyway, just some food for thought. These days, given the problems of distracted motorists, it’s in your interest to do your best to be seen well down the road. A good tail light with good batteries that’s carefully positioned is a relatively simple way to stand out.