Is it safe to cycle while holding an Umbrella?
Obviously it's at least a little less safe than biking without holding something in your left (or right) hand. But how much more dangerous is it?
Specifically, suppose that I'm biking on a flat-ish, smooth surface, on a day with almost no wind (say 5km/h), at moderate speeds (say 15km/h) and in enough rain that the umbrella is helpful.
I commute by bike every day, and have recently moved to a new location where the weather often produces these conditions, and where the folding bike and roads I ride on often lead to the above scenario. Recently I have begun riding with an umbrella in hand after observing several other riders doing so, and have fallen off thrice while learning, producing one minor injury to my toe. For comparison, I had one fall and no injuries while learning to use clipless pedals, and one other injury-free fall in the last 5 years.
What I really want to know is this: Assuming someone does this regularly (presumably like the other riders I see), is someone who rides in the conditions mentioned above 10% more likely to suffer a serious accident or 10 times more likely? In the former case, I view the enjoyment / safety tradeoff as being clearly in favor of the umbrella, in the latter I take the opposite view and will stop doing it.
Ideally I'd like to see a study on the subject, but since such a thing doesn't exist (AFAIK), guesswork or anecdotes will suffice.