Transit agencies around the country have made significant investments since the late 1990s to provide improved service to cyclist-transit users (CTUs), that is, transit riders who bring bicycles with them by using bicycle racks installed on buses. Use of these bus bicycle racks appears to vary significantly from transit system to transit system. It is unclear, however, what specific factors contribute most to bicycle-onbus boardings (BoBBs). Using multi-variate regression analysis and a detailed data set of 2008–2011 BoBBs for Northeast Ohio’s Greater Cleveland Regional Transit Authority (GCRTA), this study compared daily BoBBs to general ridership (measured by unlinked passenger trips) in light of key weather, transit service, and travel cost variables. Rates of BoBBs rose during the study’s time period and were strongly associated with weather conditions, though even in wet and cold weather, dozens of transit users traveled with their bicycles. To a lesser extent, BoBBs are also associated with transit service levels and travel costs.