There are situations when words cannot be used, e.g. during heavy wind or when someone is out of breath. Is there an universal hand signal to communicate a proposition of a chain gang behavior to fellow cyclist?
I prefer to come ahead of the other person and once I'm far enough in front of them that they can see me (but still not completely ahead of them) I'll point at my rear wheel with my right hand (i.e., the hand that's closest to the other rider). Usually they'll either pull forward ("no thanks - I'll keep pulling") or drop back slightly ("thank god - what took you so long?"). On the few times when there's been confusion I've found that they'll usually pull around you if they didn't want to draft.
There are a number of different ways to initiate a paceline via hand signals, but the most common one I've seen and used is to make a circle with an upwards pointed finger.
Watch Peter Sagan (white jersey, yellow/red helmet) do this in the following video.
He's joking in this situation, but note that his fellow sprinters all know that he's referring to starting a paceline, which is why Greipel (green jersey) checks the gap to the rest of the peloton.
Here's an easy recipe that I've seen used in a number of casual riding situations with anonymous cyclists:
- You should take the first pull, so pass the rider on the left. Make sure you're going slow enough that she can actually hitch a ride without a massive sprint.
- When your rear wheel is passing her front wheel (ie. about the time she can see you without having to turn her head), pat your upper butt/hip a couple of times on her side. This should be a friendly "come here" gesture.
- When it's safe to do so, pull in front of her. You may also consider slowing down slightly to further communicate that you aren't interested in blowing by her. (But don't slow down so much that she'll just have to pass you again!)
- Once it looks like she's on, slowly and evenly accelerate up to your desired pace.
Keep in mind that some people aren't comfortable drafting and that others may not even understand the concept, so of course this won't always work.