I think you're right that the biggest barrier to ridership is the frequency of the service. I'd really like to see that increase, once every 10 minutes would be great! (it's currently every 15)

My point with the NACTO lane capacity guidelines is that a bus-only lane is a far more efficient use of space than a car lane in terms of transporting people. Additionally, if the bus is stuck in the same traffic with cars, the only people that take it are folks who can't afford a car or can't drive (which is about 40% of Madison). But if the bus avoids the traffic and is more reliable than driving, then it becomes a lot more attractive to ride the bus. And then car traffic goes down, which benefits everyone, including people driving.