You might think that, but this has been studied and tracked. It isn't theory. The most recent local example would be Grand Ave in Des Moines. In the East Village, they removed lanes from each side and added bike lanes and narrowed the driving lanes. The accident reduction over the period of time this has been in place, has been measurable. The same can be witnessed when they did this to Ingersoll Avenue several yrs ago. Traffic calming measures really do work.