In the Large Area maps, you will always get this error along the inside and outside edges of the pavements and in the middle of the roads (on the white lines).
It's like the whole map is made in tiles, and where the 'tiles' meet (pavement edges, road crowns) there's a space that doesn't accept objects that run parallel with the join.
You just have to offset by a small amount.
There was a recent post on the forum where someone asked about creating a stadium as part of the still being updated South City layout, and Scawen thought it might be good idea to have a standalone Stadium.
So, I ported one of my old Race of Champion (RoC) layouts (used to be in the sky on SO4), down to ground level on the Layout Square to get some idea of how it might look.
The track layout covers an area of approx 179 x 92 metres, and is only setup as speed run / time trial, and the track is approx. 1 km (0.62 miles) in length. Track approx 8m wide.
Layout is enclosed, so no way to drive in and out, which the person who posted may have been thinking about.
It's possible to shrink the track lengthwise by taking about 16m off it, but not really the breadth, so track could be made to fit into 163 x 92 metre space, which may be quite big for a lot of real life stadiums.
Now converted to reverse configuration, but (as keeping the same lapper databases to record times and scores) as LA2 layout.
Set some times as I was changing signage and pit lane round. Most easily beatable, although I really tried hard to set good times with the town bus and Land Roamer mods.