Graham & 4f - I honestly don't know as i've never been in that position.
If it's small then I guess as a default then to be seen whilst running is not an issue.
I guess if you do wear stuff to be seen then that makes you relatively more considerate?
There's a guy i come across when commuting in that walks his dogs on a field that has a shared use path. He has put flashing led's on the dog's collars. Great idea. This makes him a considerate person. Does this mean that those dog walkers that don't put LED's on their dogs less considerate? Yes, relatively speaking, but not inconsiderate.
Sorry, I was being a bit of clever d*(ck - First glance at your post suggested to me they were running in opposite directions away from eachother. Hope this guy hasn't got too many dogs - Field full of flashing LEDs would be a bit trippy!