Flashing lights on their own on bikes are terrible. You don’t just need to be seen, you need drivers to clock the speed and direction of travel too, and this is much harder to do with a flashing light than a steady one. Plus, drivers might only glance your direction for a split second, your light could be OFF in that split second, so they could not see you at all.
If everything was static, a flashing light would be noticeable. However, on a busy road junction it’s not, so flashing lights just confuse the issue and f*ck everyone’s motion perception up.
I use a bright steady on the rear and a small flasher, because flashing red lights has come to mean cyclist in most people’s minds, which is fine. But if I only have one it’s steady – or maybe flashing quickly.
I am of course a motorist as well as a cyclist, and by far and away the best way to be seen is loads of bright/reflective clothing in addition to your lights. That goes for the daytime as well, which is why those BLACK nightvision jackets with the reflective overload are stupid, cos they are not very visible in the daytime.