On 2000 June 30, the NPS closed the Firehole Lake Drive because a large hole had developed on one of those wooden culverts south of Firehole Lake. That was a Friday, and with the upcoming holiday weekend, it meant that the road crews wouldn't be available to fix the problem until at least Jul 05.
I heard about the problem late that day, from some geyser gazers who were incensed that they wouldn't be able to get to Great Fountain for days. That night I realized that the situation was exactly opposite. The Firehole Lake Drive was now a backcountry area with a paved bike path through it. At dawn, well before it was time to head back out to Grand, I loaded up my bike and drove to the junction with the Loop road, and parked at the closed gate. No other vehicle was there.
It turned out it wasn't even close to time for an eruption of Great Fountain, but I had the area to myself. My next visit was on Jul 02. By then, a few people had figured the situation out, but as this video shows, it wasn't many.
I made one more visit on Jul 04, and the road was repaired and reopened the next day.