Jennifer Dill (twitter) has recently written a blog post with a quick overview on the research on bicycles found in the Web of Science since the 1930s.
Although we don't know how the 'bicycle literature' has been growing relative to all publications in transport/mobility, there is a good sign there is boom in bicycle research! The method used by Jennifer to identify the publications is not supper systematic but it's insightful anyway. Jennifer's blog post is a quick and interesting read.