D020 was obviously rerouted east of İstanbul. It doesn't begin at O1 anymore but at Kurtköy.
wikipedia calls the westernmost section "D020-07". They indicate its beginning at O4's K41 exit. It's an unsigned O4 branch which we have as
tursf route now. The first short D020 segment from here to right after the O4 main line underpass is unsigned according to 2023 GSV. GM indicates the segment as D020, OSM not. Nonetheless, I'd include the segment to D020.
The rest of the rerouted D020 - mainly in parallel to O7 - is signed well.
Some examples:
D020 is signed at O4 onto O4's unsigned branch (I think it's a "To D020". There are only white signs w/o any road numbering afterwards (
example).
First D020 just after the O7 underpass.
D020 on 2018 GSV at Paşaköy, i.e. right after the junction where the new routing branches off from the old routing.
No numbering at the junction where old / new routing divertes.
A note from August 2022 about D020:
The western extension of O2Sul is in HB as O1Lib. OSM calls it D20, GM has no numbering and I didn't spot any numbering on 2021/22 GSV (quick check only).
The old routing (no TM traveler) is a grade-separated dual carriageway except of the easternmost segment. I'll add it to tursf system.
Edit:
https://github.com/TravelMapping/HighwayData/pull/6923
