Don't have the energy (ha) today to do a detailed read, but something like this should give some clue:

http://www.imedpub.com/articles/avia...visibility.pdf

One sentence early on reads: "It is stated that an intensity of 350 cd is required for a signal light to be
visible from 0.125 miles away in conditions corresponding to a runway visual range of 0.125
miles".

So, 1/8 of a mile requires 350 Candela (in a runway setting, where there might be more contrast with ground items?) We probably want 1 mile ideally? So, some math converting Candela to Lumens (which is what is reported in the specs for strobes) would get you some rough approximation of the lumens required to be visible over some reasonable angle (steridians). A very quick back of the envelope tells me that a bike strobe (typically 200-400 lumens) is several orders of magnitude too weak to be useful. Maybe someone has the time to run numbers and make sure I didn't add when I should've divided etc.

P3