The case of negative externalities in the Kantian Model could be exemplified by the “tragedy of the commons”. Here is a daily Mexico City example of its implications:
Public roads are an excellent example of common property shared by many people. Each of these people has his or her own interest in mind — typically, how to get to work as quickly and easily as possible. But when everyone decides that public roads are the best way to meet traveling needs, the roads jam up and slow down overall traffic movement, filling the air with pollutants from idling cars.
Turning public roads into private roads or toll roads creates a different scenario. With a toll to pay (especially if the toll is higher during peak-use hours such as rush hour), drivers may consider a less-direct route or choose to drive to work at a different time.
Given this example, could one find a possibly Kantian equilibrium which is Pareto efficient?
Externalities given by the amount of cars in the public roads are all negative?
I believe we should consider the existence of both types of externalities. Let´s say Bob´s wife prefers him to go to work in his car cause i he doesn´t, he will eventually arrive at home very late. Thus, if Bobs chooses to take his car to work, he is making a positive externality in his wife´s welfare but surely he would be being a marginal responsable of the daily heavy traffic.
Given this, we should find an reallocation of individuals actions such that it holds Pareto efficiency. Is this true?