There are 578 roads in Mexico on Forza Horizon 5, but for this achievement we need 573.
Best way is by turning down the brightness to 0 on game setting, which makes it way easier to spot missing roads.
Top 3 roads which you might missed:
- North East Beach
PLAYA TRANQUILARed road which most of players didn't complete, since the story mode stopped at middle of the road and probably most of the players didn't drive to the beach with this road, even if it shows red for you.
- Town called
GUANAJUATOUnderground tunnels might be the road which you missed, take a try. On the map bridges and tunnels are shown different, compared to regular roads.
- On top of two farm circles at
DE OTRO MUNDOSmall road which looks like a letter L.
Also there is a bug in the game, when on the small radar it will show red, but on the map you can see it is missed with grey colour. In this case I recommend to check all red rally roads, maybe something is missing.
Example of the bug you can see on these screenshots.
I hope it will help you to find them all :)