A problem that I'm always confronted when cycling, especially in steep climbs where there is no or insufficient roadside, are cars passing too closely. Usually I would position myself more close to the middle of the lane, but the speed incompatibility it's just too large and drivers aren't very educated where I live.
A idea that I had is a simple semi-flexible foldable pole on the left side of the bicycle that I could put on those situations, so it would "force" drivers to pass with a larger distance. Of course it would have some kind of reflective flag or, even better, a strong LED (as the flag would offer more wind resistance, and the LED would show up better at night), and it would have to be flexible enough for not knocking me over when someone hits it.
Of course that already exists (safety/flash flags), although is not very common. But the "mind storming" was still nice.
Another problem that I face sometimes is when I'm cycling on the roadside but then there is a new lane that turns to the right. My options are keep going on the roadside (and later on the new lane), but it would make the drivers turn abruptly in front of me (or over me), as they might think that I will turn too (and that is a reasonable idea). My second option is to enter the right (now middle) lane, but the speed mismatch (and the need to position myself close to the middle of the lane) doesn't allows it. The flag would make the second option easier, and it would tell drivers that I'm not going right. For illustration:
My question is the following: Will it be useful, and will it be safe? Is there any other option? The idea is to retract (fold) it always when not using, and not to use it when cycling in group, so it wouldn't bother other cyclists. And is worthy to mention that the roads I ride have a 50 mph limit (although speeds up to 60 mph are common).