I've discovered some of these commands, the rest is documented in GP2 track editor

command format:

byte

0 argument 1

1 command number

2-3 argument 2

4-5 argument 3

... ...

this may be weird sequence of bytes has its logic. On Intel platforms word is stored with low byte as the first and high byte as the second. It also seems, that all commands have even lengts, which implies that the first argument is only one byte long.

these commands are used to draw Phoenix and Interlagos tracks

Command length meaning

0x0 2 sector length

0x80 4 object placement

0x81 4 display distance front

0x82 4 display distance back

0x85 6 track width change

0x86 2 connect pit lane start

0x87 2 connect pit lane end

0x8a 12 track markings

0x8b 12 starting grid markings

0x8e 6 left kerbs begin/length

0x8f 6 right kerbs begin/length

0x92 4 ??

0x90 4 ??

0x94 4 curve polygon subdivision (1=many polygons, 8=few polygons

0x95 4 may be the same as 0x94

0x98 4 left fence height change

0x99 4 right fence height change

0xa1 2 pit lane entry, join rigth pit lane fence

0xa2 2 pit lane entry, join left pit lane fence

0xa3 2 pit lane exit, join rigth pit lane fence

0xa4 2 pit lane exit, join left pit lane fence

0xa5 2 ??

0xa6 6 ??

0xa7 6 ??

0xa8 2 marshal with a flag

0xab 6 ??

0xac ? GP2 editor says, it's a palette change (may be)

0xff 0 last command - used behind last record of track data