The last point is motivated by the fact that different cars have different options, and occasionally also at different times. Heavy vehicles would not be allowed to travel on the lightest beams, for instance. Or cargo-vehicles carrying combustible goods might not be allowed to travel on certain routes. But when not carrying combustible goods, they would be allowed to use those routes. It only has 10 nodes.
Some connections are only one way.
Starting at node 1 and using it as departure node, then, going to node 2, one gets 15 minutes travel time. Going from node 1 to node 6, one gets 22 minutes. Then there are no more immediate destinations to be reached from node 1, so we move on to node 2. We get no listing towards node 7, because that connection is one-way in the opposite direction . After node 2, we move to node 3 and, using 3 as departure node, calculate the travel times to neighboring nodes in a similar fashion.