Germany's autobahns are renowned for average speeds well in excess of 80 miles an hour, but the average dropped near zero as tens of thousands of people sat at a 37-mile table for a cultural celebration entitled "Still Life."
The event was part of a wider cultural festival celebrating the Ruhr region. It was chosen by the European Union this year as a European Capital of Culture 2010 - the first time the distinction went to an area rather than a city.
A festival spokesman said an estimated three million people turned out amid fine weather, one million of them with their bicycles, to celebrate on the highway between Dortmund and Bochum, in western Germany. Tens of thousands sat at the table, which was made up of 20,000 individual tables.
"Attention on the A40," a radio traffic report warned. "There is a 60-kilometre (37-mile) closure between Duisburg and Dortmund due to the longest table in the world."
The highway, which crosses North Rhine-Westphalia state, is normally one of Europe's busiest.
Germany has no general speed limit for its famous autobahns. Cars often speed up to 125mph or more. In dense or dangerous areas, drivers are often required to slow down to 75mph.