Upgrades to roads/transit are part of zoning decisions. Where a developer wants to go beyond the current zoning and increase density (most all situations) they are often forced to contribute to infrastructure improvements. Even where they aren't, well-run cities do not allow development ahead of the infrastructure to support those new residents.
One parking spot per unit is no longer a norm. I know of developments with perhaps one per five, with most not coming with any assigned spots. But it isn't really just the parking. It's the lack of buss stops and adequate foot crossing and the increased traffic of all forms on local bridges. Pretending that everyone will just use bikes, or that they are old and won't go out much, is a convenient excuse to bypass good city planning.
Interestingly, closing roads and reducing the number of cars would improve the number and availability of foot crossings. It's funny you mention good city planning, since a lack of good city planning is actually why we are in this situation in the first place.
One parking spot per unit is no longer a norm. I know of developments with perhaps one per five, with most not coming with any assigned spots. But it isn't really just the parking. It's the lack of buss stops and adequate foot crossing and the increased traffic of all forms on local bridges. Pretending that everyone will just use bikes, or that they are old and won't go out much, is a convenient excuse to bypass good city planning.