I like using the bell which seldom gives me negative results, and I have a air horn for real emergencies. There's a heavily used rail-trail near Chicago paralleling a busy rail line. When a freight comes rumbling through about the only way you can warn anybody your intentions to pass is from a slight blast of the air horn. Occasionally when I have given a verbal warning "On your left" instead of using the bell I've had people actually go to the left. Of course, kids are very unpredictable like most of you already now; you never know what they're going to do.