The odd thing is I can’t see how the trip by car would be quicker than by train. The train frequency was around 3-4 minutes – any shorter and each train would be lucky to have 15 passengers. Train speed was up to 200kmh. I watched one of my trucks caught in the jam travelling to an industry half way between the towns and the train must have passed it at least 10 times. Each bus or tram route in either city has 3 vehicles per line and max frequency is 3 mins. Each city has 3 or 4 lines and each land use is connected.
I think you’re right in that the AI doesn’t detect an inter city connection unless you make one. Once the connection is severed, the AI ceases to see the connection. I found it amusing that I provided a fast connection but the agents would rather sit in traffic. When I took the service away, they no longer wanted to travel.