In keeping with the subject in the opening post; If you are going to use a rear lamp during the day it has to be extremely bright and at a very "attention getting" flash setting. Otherwise, in full daylight I really don't think it would be helping.

I agree 100% about wearing a the bright daytime color jersey or jacket. The only color I wear on the road is the extremely bright daytime yellow. IMO it is the best color to wear but the neon green and fluorescent orange are pretty good as well.

I have at times used a rear lamp in the daytime ( rear ) but only when on really busy roads with fast traffic. I will however turn my rear lights on once the sun is lower in the sky. My daytime rear lamp is a torch I have mounted to my seat. It has an amber XP-G2 led and uses a reflector. The flash pattern is a triple flash/pause. I like it, very attention getting but it might only be about 150 lumen ( custom driver/over-driven ). I've considered buying the DiNotte quad amber to replace it but I want to be sure the DiNotte will hands down be at least twice as visible ( "At Distance" ) before I lay down the big money. ( Sadly if I want to do that I'll have to buy one and then decide if I want to return it ).

Now someone might wonder why I would want an "amber" lamp for the rear....well, to be to the point, I want to stand out, be different. I know someone will say that the red LED's are brighter...I know that. If you've never seen a good extremely bright amber lamp you wouldn't know just how attention getting they can be though.

I've seen good rear ( red ) bike lights in use during the day. The good ones use a very bright flash mode. Last year I came up on one guy using one. I could see his lamp from almost a half mile away. ( before I even knew it was a cyclist ). It was funny too because he was riding with another guy who was using just a cheap rear led, his I could barely see and wouldn't have even noticed if it wasn't for the other guy with the bright one. The difference between the two was like the difference between night and day. I don't know what lamp the guy was using but when I caught up to him I wound down my window and let him know how well his lamp was working.

Being hit from behind in the daytime is very rare. Prepare in proportion to the risk. Know your risks.

Get some Dinotte Lights.

I have stopped traffic Five times with mine.

Well, yeah..a PBSF in the daytime isn't going to be that much of a difference. Hi-Vis yellow has finally become very popular in my area.

I still think the PBSF's do a decent job as long as owner is using good batteries and has it aimed properly. I wouldn't recommend one for increasing "Daytime visibility" in full sunlight though. If used in the late evening they are still pretty visible as long as they are being viewed from directly behind. Of course with the newer/brighter stuff available I don't know why anyone would buy one unless they just didn't have the extra cash to get a better light.

Meh...I don't know about that. The newer versions of the typical 40-80 lumen rear lamps do a really good job at getting a person seen and at the $35-$50 price level they are affordable for most people. You can buy brighter lights but then the price starts to go up and not everyone is willing to drop over $100 for a rear lamp. That said when I go out to the bike stores I look at the available rear lights and most of the ones I'm seeing not only will work very well at night but do a decent job on a dark over-cast day as well ( when on flash ).

Now if the manufacturers of the current brands of self-contained rear lamps can increase the output to say over 200 lumen and can still manage to keep the lamp body small, the price under $75 and the run times over 3hrs ( assuming a self-contained USB charging unit ) then yes, the old will fade away and the new will take it's place.

....one would hope. Then again there are likely no statistical facts having to do with cyclist's who use exceptional safety equipment vs. cyclist that don't.

As to which would be the greater risk; riding in the day vs. riding at night, a lot would have to do with traffic conditions but otherwise I would consider that it might indeed be safer to ride at night if the person doing the night ride is using a very good light/Hi-Vis set-up ( both front and rear ) and the traffic conditions are not extremely fast or heavy. Of course motorist might not be expecting to see cyclists at night so that too plays into the safety factor of riding at night. Either way, day or night a person on a bike never knows what to expect. Likely at night more tired, distracted and/or inebriated motorists, always a thought to consider.

More people ride in the day though. That's just the way it is. If people wear some hi-vis color they should be fine. Add some ultra bright rear light and it should help but just how much is anyone's guess. Either way more light is not going to be a detriment unless of course you are allowing "the geek factor" to be called a detriment.

As an employee of a large company I am required almost every other month to take drivers safety training as part of my job requirement. One of the things that was pointed out on the last test I took was that 80% of all road accidents involve rear-end collisions. From a cycling perspective that's not encouraging but most people who ride bikes most of the time aren't riding directly in the road-way. However, if one were to ride in the road because they had no choice that would raise the risk of being hit...statically speaking.

Personally I seek roads that have wide shoulders or have little traffic. If I'm on a road with little shoulder ( or none ) with heavy traffic I am extremely antsy. In those conditions I feel a little better if I have some good rear lights going.

I doubt that 80% figure. Do you have a citation? Furthermore, riding in the roadway is safer than off to the side, which may go against your intuition, but there it is.

Percentage of collision direction is going to be EXTREMELY subject to local riding conditions.

On the route I ride, it would be almost impossible for someone to hit me from the front. I'm riding miles and miles down high speed roads with very rare driveways and intersections.

On routes in cities that involve a lot of pull-outs and left turns, I'd imagine that being hit from the front or being pulled out in front of would be much more common.

There's just no way that a single number can quantify risks for all cyclists. You could probably create a stat that indicated that 80% of all bicycle accidents were caused by protruding tree roots if you sampled the right cyclists.

The driver training program is something that is created outside the company. We used to use "Smith System" but a couple years ago they switched to another program that is accessible to the employees via the internet. Sorry but I forget who or what company produces it. Who knows where they get their figures. (?) I doubt the ( 80% ) number is representative of all jurisdictions. If you live in a rural setting the number is probably quite different. Oh, almost forgot to mention; the 80% number had to do with "motorized traffic". I only mentioned it because like cars, bikes use the roads too. How that 80% number relates to bicycle accidents is anyone's guess. The point I was making though was that motorist often times aren't paying attention to "what's in front of them".

Tom, about that "riding in the road is safer"...( lol ) I'm not sure I can agree with what you said. It might be true when approaching intersections or something like that but on roads with high speed traffic I'm going to listen to my gut that's telling me to ride on that very nicely paved shoulder.

Most traffic statistics are on a state or national level, and that would smooth out the problem of small sizes like the one you're speaking of. You make a valid point which is that a well sampled survey may not apply to an individual's situation, but statistics are useful anyway, especially if, over your lifetime, you are going to be riding in a variety of conditions. I bet most people won't do most of their cycling on divided highways.

My first year of commuting was on a bike that has cheap hub-powered lights with no flash mode.

My 2nd bike didn't come with lights so I got a set of Lezyne USB-charged lights, which do have flash modes on both head and tail. I've noticed drivers hesitating to pull in front of me with this setup, whereas when I've ridden the other bike, they just pull in front like I'm not even there. I generally prefer riding on the street over the sidewalk, but I do have to ride on sidewalks/MUPs that cross streets and parking lot entrances for small segments of my commute, in order to access bridges.

Not sure if there's a difference between slow and fast flash modes.

I have a colleague who doubles up on his lights - two in the front, two in the back.