Books
The road suddenly turns out to be impassable because it's being rebuilt by the Chinese, only we're not supposed to know that. And exactly what is meant by 'suddenly' I don't know because they've apparently been at it for ten years.
— Douglas Adams ‧ Last Chance To See
Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Adams describes a road that is abruptly closed because of a rebuild nobody is meant to mention. Then he questions 'suddenly', since the work has apparently run for ten years. Broken pavement fits the joke: a long-running roadblock dressed up as a surprise.
Context reviewed