Michigan Avenue north of the Chicago River is famous for its traffic jams, with buses competing for road space along with private cars and taxis. Given how closely packed vehicles can be at times, it's inevitable that a crash could occur faster than anyone could respond to even when fully alert. The hazard of this stretch of road was demonstrated quite well in this latest incident:
This stretch of roadway, which serves some of the largest hotels and shopping centers in the city, hosts twelve bus. The number of full-time routes is five between Ontario and Chicago, dropping to four north of Chicago. This is still a significant number of bus routes on one street, justified by the shear demand (I've often ridden a 147 that filled up completely before entering Lake Shore Drive).
The problem with so many bus routes is that it creates a lot of demand for the right hand lane (in order to pick up passengers). The problem is that the taxi cabs need to use the right hand lane as well to pick up passengers. This can create a lot of lane switching from the left lane to the right lane which provides ample opportunity for collisions.
One simple solution would be to prohibit private cars from using Michigan Avenue north of Ohio. Cars could be directed to use Ohio to reach Lake Shore Drive via Columbus and Grand. For those starting their trips from the Loop it would be a simple matter of directing them to go east on Jackson, Monroe, and Balbo. This would complicate trips for many travelers but it would be the most effective method of utilizing limited capacity: reducing the number of vehicles. There is still some flexibility and opportunity in the downtown lakefront area for modifying streets. Michigan Avenue has no such flexibility; expanding the capacity would either require demolishing the median which has some cityscape value, or destroying sidewalks.
A second solution would be to designate the right hand lanes of Michigan Avenue for buses and taxis exclusively. This could be combined with using articulated buses to increase the capacity of the routes without adding more vehicles.
Another problem with so many routes on the same street is that there is a bus on almost every block stopping to pick up and discharge passengers. This essentially brings 33% of Michigan Avenue's capacity to a dead stop. Converting North Michigan Avenue to free area would dramatically reduce boarding times; any lost revenue could be made up elsewhere.
Boarding times could also be reduced by installing a system similar to Curitiba where passengers pay to enter the bus shelter and then board the bus through platforms. The wider sidewalks on North Michigan Avenue could allow for such a system.
The overall problem with North Michigan Avenue is that there are simply too many vehicles. New residential developments and economic growth will only make this situation worse.