Many to Many field with a context field which is another relation?

[wiz256]

Summary

I have collections:

cities (id, name)
routes (id, name)
routeCityStops (id, routeId, cityId, address, departureTime)
routeFares (routeId, cityFromId, cityToId, priceValue)

What is the best way to show in routes item details all routeFares belonging to this route as a table with ability to add/modify routeFare records?

Many2Many did not help me because routeFares has 3 relations (because of cityFromId, cityToId and routeId).

How to properly configure such setup for model with Route and RouteFares?

Motivation

Need to support "tripple" relationship like for routeCityStops in:
cities (id, name)
routes (id, name)
routeCityStops (id, routeId, cityId, address, departureTime)
routeFares (routeId, cityFromId, cityToId, priceValue)

Requirements List

Basically I want:

1. being on route item details page to see all routeFares related to this route with cityFrom, cityTo and price values
2. when new routeFares record is added from routes item details page then routeFares should get routeId automatically set (as we are on that route details page already).
3. when editing or creating new routeFares record from either from within routes item details page of from routeFares list page we should be able to select only those fromCityId and toCityId which were assigned as available stops through routeCityStops collection.

Alternatives

Maybe there is already some easy way how to configure it.