This is the 2804th most frequent Japanese word.
開通
"Opening" or "completion of a route or service (e.g., road, railway)."
開通 is used here to refer to the opening or operational commencement of the new road.
新しい道路の開通を祝う式典が行われました。
A ceremony was held to celebrate the opening of the new road.
開通 in this sentence implies that the tunnel will become operational next month.
このトンネルは来月ついに開通の予定です。
This tunnel is finally scheduled to open next month.
開通 refers here to the act of making the internet line available for use.