When people use bicycles and scooters, or walk instead of take a taxi to work, they save the environment one act at a time. This may not be a huge boost, but it will in the end bring a huge change, and so city planners sould work harder for this.
City planners should work harder to discourage people from using cars, but they have to provide alternative means to people and convince them. A free train would be great. When I was in many South American cities, the subways and trains were completely free of charge. And that is incredible.
No, the use of cars is the number one way of transportation that we have today, and I think that the people are never going to want to completly stop using cars even if they are in the city. I think that they need to just stop the amount of large vehicles.
No, American city planners should not work harder to discourage people from using cars, because it is a person's right to use a car if they want to. Often, governments try so hard to implement public transportation that they put systems in place that are not cost efficient and that very few people actually use.
Driving is entrenched in American society so for city planners to discourage car usage would be a mistake in my opinion, I believe that improving the existing mass transit system to be more comfortable and more efficient would be a better idea, I think that overall city planners should not discourage car usage but find ways to deal with it.