Since June 11, the Norris to Mammoth road has been closed nightly from 10 pm to 7 am (excluding Saturday nights). The word is to expect 30-minute delays in the daytime when driving between Roaring Mountain (the magenta dot east of the road on this map) and the Indian Creek Campground (the tent icon down a short side road, almost opposite the Sheepeater Cliff picnic area). According to trip reports on the Facebook group Yellowstone Up Close and Personal, the daytime delays are usually not as long as 30 minutes.
The important news is that from September 10 (10 pm) to October 6 (7 am), this section of road will be closed to all traffic (day and night). During the closures, people will be able to detour over Dunraven Pass (between Tower Fall and Canyon).
Norris and Indian Creek Campgrounds, at opposite ends of the road segment, are remaining open during the season. During the road closure you will not be able to see Apollinaris Spring, nor Obsidian Cliff, nor will you be able to hike the Mount Holmes Trail. You can still hike the Bunsen Peak Trail from the north.
Remember to check the National Park Service’s Park Roads page before you head out.
CREDIT: Linton Brown revised this map for Yellowstone Treasures, Updated Fifth Edition (2017). You can find it on page 277.