If SCS ever expands to Asian side of Turkey I believe this topic could be useful for them.
First off, here's major motorways;
O-4 Which connects Ankara to Istanbul.

O-5 Which connects Istanbul to Izmir.

O-31 Which connects Izmir to Aydın. (pink section is planned)

O-21 Which connects Niğde to Çukurova region. (pink section is in construction)

O-51 Which connects Mersin to Adana. (pink section is planned)

O-52 Which connects Adana to Şanlıurfa (pink section is planned)

I believe this could be very helpful if SCS ever decides to build the Anatolian part aswell. You can also comment down if you also got other information.