Obj Files not loaded correctly

When attemping to load This Model into Object Viewer I got this: It seems there are problems with depth sorting, and texture and material matches got into a COMPLETELY MESS.

... While it works just fine in the 3d modeling software.

Also the modeling software is able to load this model at a much faster speed than openBVE. Where's the difference?

Will take a look & see what I can do.

The short answer as to why it's faster though is because the openBVE parser was written by me, and is probably a lot higher level than what the modelling software uses
It's not bad, but certainly not brilliant. I may be able to make some things a little faster if I can measure the slowdown with this model at my end.

Will also investigate the depth sorting issues.

Edit:
Fixing the negative vertex indicies (your other post) has made the depth sorting issues go away
This is definitely a little slow to load though, will see what I can to, although that may take a little longer.

OK, try this build:
https://vps.bvecornwall.co.uk/OpenBVE/Builds/OpenBVE-2018-07-01.zip

This removes a duplicate vertex check, and so may use a little more memory, but the model in your OP now loads at a sensible speed, and with no glitches I can see
Not sure I'd recommend using it too often due to the sheer number of vertices in the thing but there we go.