Clyde1820

Yes, I believe they are.

In my area, there's a particular quality of the light that combines with the background colors and hues, such that it can be incredibly common to see a cyclist seemingly blend in with the background. Until getting quite close. I haven't seen that everywhere I've ever been, but it sure occurs where I live.

Cyclists who have two or more "daytime" flashing lights end up vastly more visible (to me) than otherwise. Granted, those are just my own observations from seeing hundreds of cyclists on various roads, but it sure seems to help. With brightly-colored (ie, DayGlo Green) jersey or jacket, visibility is improved further.

I also frequently see that the cyclists with two or three exceptionally-bright "daytime" flashers also get a wider berth from following vehicles.

If riding frequently on roadways with lots of following vehicular traffic, my own preference is for: one very bright flasher on the back of the rack or saddle; one very bright flasher on the seat stay, down lower, flashing a different pattern; and a flasher on the rear of the helmet. Pretty darned visible, by comparison to having none or even one.

I suppose the benefits in your own area would depend on conditions and lighting. But I can't see how it could hurt to have as much high-viz rear lighting as possible.

While there are some brighter ones on the market, I've used this one and have been impressed with the visibility: Bontrager Flare R rear light.

Here's a useful website of reviews: Reviews @ BikeLightDatabase.