[mgolawala]

That is not a problem of population density, that problem is inadequate peak capacity in transportation infrastructure. For example if you stack subway lines one under the other simalar to those described by Elon Musk, or increase the capacity of the existing public transport system through through faster & more frequent trains, you can resolve such issues. You just need to commit to spending on the infrastructure to support the population density.

Interestingly, it is policies like prop 13 in California that restrict the revenue needed to invest in the infrastructure to support higher population densities.