This is a pic, although a bit deceptive, about the space used for different modes of transportation. The cars and bikes are parked so if moving would take up more space. There is only one bus but again if moving they would take up more space when moving. The take away though is that buses can move lots and lots of people. In fact, except for a few central business districts, we have plenty of roadway to move people if every took their trip on a bus in almost all western cities. Combined with electric kick scooters, bicycles, and kick scooters where bus service is lacking a large impact on traffic congestion is possible. (found pictures from this blog)
Design & Geography 
Based on the pictures above, the pollution will be very high considering the use of cars while the use of buses will not be as much in terms of pollution because it has the capacity to carry many people at a time. As per the bike/scooters that are using electric, there will be no pollution which is an advantage but congestion will be high. .