For everyone attending the Istanbul show, this is what I found (after a veryyyy long search btw) on a Turkish U2 FB page. I think it's very useful info about the different means of transportation.
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While you’re getting ready for the biggest concert ever organized in Istanbul, you are welcomed to join in the activities at the event zone after 01.00 pm. Stadium gates will open at 5.30 pm.
Arrive early, use public transportation! In ord......er to avoid the probable traffic jam, arriving early and using public transportation is essential. For additional meeting points please follow
U2 360° Tour İstanbul 06Eylül'10 and
Biletix .
Arriving to the Stadium
You can take the metro, the tram, the metrobus, the bus or the dolmuş (shuttles) to get to meeting points. We suggest you to buy 5-piece tickets from İETT ticket booths before the event.
Meeting Points
There will be İETT buses going to the stadium regularly. By using metro, tram, metrobus, dolmuşshuttle) or bus from central locations such as Taksim and Zincirlikuyu, you can easily arrive to our meeting points.
For a roundtrip ride to the stadium, we suggest you to buy 5-piece tickets from İETT retail points before the event.
TRAIN From Sirkeci to Halkalı, every 15 minutes
METROBUS Avcılar-Zincirlikuyu-Sğütlüçeşme line to Yenibosna
LIGHT METRO Aksaray-Havalimanı line to Yenibosna
BUS From all central locations to Yenibosna
Taksim(between 12:30-17:00), Halkalı and Yenibosna (between12:30-20:30)are our meeting points for the show. There will be İETT buses going to the stadium from these points regularly.(The cost is 4 tickets for the roundtrip)
Coming Back From the Stadium
All the routes aforementioned are valid for going back to the city. With extra IETT buses after the show, you can get off at Halkalı for the train and Yenibosna for the metrobus, the light metro and the bus. There will be no Taksim buses at that time.
Private Transportation
Stadium’s parking lot’s fee is 10 TL. Capacity is limited.
You can come to the parking lot from TEM highway’s last exit before Mahmutbey toll booths.
If the Stadium’s parking lot is full, all the coming vehicles will be welcomed to ISTOC parking lot. There will be free shuttles to stadium from here. These free shuttles will also be available after the show.
PS: East-north roads are closed due to construction, only west-south road is available.
Enjoy the show