I am using Google ortools for CVRP. I have constraints on both vehicle capacity and max distance (in reality, it’s a max travel time constraint, but I’m formulating it as a distance constraint). Both constraints are holding. The issue is that my max travel time constraint, in real life, is a goal: at least XX% of routes under the maximum time. So I don’t need 100% of the routes to meet this constraint, but X% – and in fact, if 100% of the routes were under it then that may be suboptimal for the business.

I have a distance matrix with first row and column set to zeros. I try to run the code provided on the VRP website (Or-Tools) and it provides me with the following solution. This is obviously not the correct solution since a vehicle cannot hit all the places with a total distance of 0m.

I would like to study in detail how OR-Tools works for VRP.
As I understand it, the solver first finds some feasible solution and then improves it by local search methods.
Is there a detailed description of how OR-TOOLS algorithms work using different parameters for first_solution_strategy and LocalSearchMetaheuristic?
Is there more detailed information about the parameterization of the solver than https://developers.google.com/optimization/routing/routing_options