You shouldn't have to run for the bus because there will be frequent buses and live tracking letting you know exactly when the next one is coming. 
There are platforms for boarding so you don't have to cross through traffic to get on. Think of it this way, normally, depending on what side of the street you're on, you either don't have to cross the road at all, or you have to cross both directions of traffic. In the middle, you only cross one direction of traffic to get to the bus. 

As far as the projections, they aren't saying 100% because they aren't just making up numbers. These are realistic projections based on service and travel times and cost and socioeconomic data and studies of similar systems.