The article explains it all.
What was for one year a 'scenic parkway' through the woods was doubled in width into a hazardous "roller coaster"
The beltway was not widened to 8 lanes until the 1990's. Somehow, there is still a short 6 lane section and even a 1/4 mile 4-lane section abutted by 10 lane sections. What about the traffic jam? Non existent according to traffic patterns.
While the eastern half of the belt was always 6 lanes to serve as an I-95 bypass, the Western portion in Virginia opened with a quaint 4 lanes. I-95 through DC was never completed.
The exit numbering system is an ever-changing jumble, and is explained as clearly as possible by the article. Locals tend to refer to exits by crossroad.
The proper term is Capital Beltway (named by Maryland and Virginia together), not Capitol, to indicate that it served the area and not just the city or that big-domed building (the 'Capitol' beltway project was a totally different urban renewal effort).