Ok, I've had this theory all along that the sim called flavor 4 in the immediate foreground, then nontextured polygons in the distance
(I thought one set was fl2 but I was wrong, its fl1 sections called 2X). Notice below,  in the 1st batch of fl12's, once again each distance variable is divisible by 620165.

Batch 1
This first group of sections defines from the start line at michigan  through the 1st 826.88666 feet.
these flavor 12's are removed from sections that call to textured polygons, notice that the sections are short (probably to save memory). I define this as the immediate foreground when you are in the sim.

FL12         86712           0      620165      570000      870000
FL12         86732           0      620165     -190000      570000
FL12         87816      620165     1240330      570000      870000
FL12         87836      620165     1240330     -190000      570000
FL12         89040     1240330     1860495      570000      870000
FL12         89060     1240330     1860495     -190000      570000
FL12         90104     1860495     2480660      570000      870000
FL12         90124     1860495     2480660     -190000      570000
FL12         91168     2480660     3100825      570000      870000
FL12         91188     2480660     3100825     -190000      570000
FL12         92392     3100825     3720990      570000      870000
FL12         92412     3100825     3720990     -190000      570000
FL12         93456     3720990     4341155      570000      870000
FL12         93476     3720990     4341155     -190000      570000
FL12         94680     4341155     4961320      570000      870000
FL12         94700     4341155     4961320     -190000      570000

Batch 2
Notice how each segment is divisible by 620165. only each segment is 2* in length then it was before.
each segment is defined by flavor1 (plain poly)...I define this segment as the mid vision point

so when you are at 0 in your car, this batch will call 2* farther down the track then the 1st batch did but it will not display polygons.

FL12         95152           0     1240330      570000      870000
FL12         95172           0     1240330     -190000      570000
FL12         95620     1240330     2480660      570000      870000
FL12         95640     1240330     2480660     -190000      570000
FL12         96088     2480660     3720990      570000      870000
FL12         96108     2480660     3720990     -190000      570000
FL12         96556     3720990     4961320      570000      870000
FL12         96576     3720990     4961320     -190000      570000

Batch 3
On to batch 3
notice now that each segment is 2* in length from the previous batch. Each segment is defined by flavor1 (plain poly's)

when you are at 0 in your car, this batch will display the plain polygons that you can see far off in the distance.
 

FL12         97024           0     2480660      570000      870000
FL12         97044           0     2480660     -190000      570000
FL12         97492     2480660     4961320      570000      870000
FL12         97512     2480660     4961320     -190000      570000
 

FL 17 defs

FL17        251524           0      620165     1240330     1860495
FL17        251580     2480660     3100825     3720990     4341155
FL17        251636     4961320

each number is divisible by 620165
in fact you can look at flavor 17 as

fl17     (620165*)  0       1        2        3
fl17    (620165*)   4       5        6        7
fl17     (620165*)  8   (next f12 section call begins)
 

thats it for now.
Brian