As you can see from the below screenshot, my transport adviser is telling me that I currently have no access to the region;
The screenshot also shows a road linking my city to the region, I have the traffic data layer up which shows high levels of traffic on it, although the overlay is showing as orange rather than red, so it's not exactly gridlocked, just moving slowly – zooming in even shows people leaving and arriving to the city via the regional highway!
Normally you would get the 'No Access to Region' message when you've not got a road connected up to the regional highway. Can heavy traffic also disconnect your city from the region, or is something else going on?
Best Answer
The road advisor deeply cares that all of your buildings be attached to the region. If any buildings are not connected, he will complain that there is no region access. In the above picture, I have demolished some roads and some decorative cinderblocks are left behind. Since this former decorative part of an industrial zone has no road, it has no region access.
If you hover over the little triangle by the advisor's head, then click on the little red road icon, you can cycle through the occurrences of such buildings. This works for fires, crimes and abandoned buildings as well, from their advisors.
I have tried to connect my cinderblocks to a road, but the roads do not cooperate. As a decorative building, it's immune to direct bulldozing. I just let the road advisor worry about it.