In many places it's illegal to enter the intersection (even if the light is green) if you're unable to immediately leave it, mainly to ensure that intersections don't get blocked if there's a traffic jam in the direction you want to go; and this rule also prohibits (not everywhere) to enter the intersection for a left turn if you can't complete the turn right now because there's still oncoming traffic.

Ahh now it is finally clear.

Then the laws in Pittsburgh are just bad. Not a design question at all.

Here you oull into the intersection on green, turn slightly ti a big white cross on the road for exactly this purpose and go when it is clear. This happens when the oncoming side has red, but before the crossing cars have green. The time between red and green is long enough for all two or three cars to clear the intersection.

Get better laws i guess?