While I don't know of the safety impact of removing left turns, the actual trip time impact in a busy city is severely understated. In my city (700k people), an old European town, city center has seen the removal of a few key left turns in the past few years.
Consequences for traffic outside city center: probably none.
Consequences if you want to drive from within the city center to the outside (e.g. go back from a shopping mall / restaurant / business meeting): walk further (many places to park are inaccessible) back to the car, drive a block or two more than you normally would. Extra time: +5 minutes to walk, +10 minutes for those 1-2 blocks (traffic is heavy).
Now the "best" part: Consequences if you want to drive into the city center: you need to make a sequence of correct turns 1-2 kilometers before your target, and if you don't, you are punished with extra 20 minutes in traffic at least (and still won't land where you wanted) - there is simply no route to where you wanted to go unless you pick 1 specific ideal route which many drivers don't know. Results: if you know the city / have good gps (Google Maps sometimes gets it wrong) +10 minutes in traffic, if you don't - + 20-30 minutes in traffic.
[edit] You may ask "why you can't do a triple-right-turn?" that's because the city center is not a grid. Many streets are don't have cross-paths for long stretches around historical part of the city.
Now the really painful part...
Your trip outside the city center is only 5-10 minutes.
Losing an EXTRA 20 minutes is a huge loss, it makes the ttrip almost as bad as walking - but inside a car. Bad for everyone really.
My main beef is with the fact that many places in the city become almost inaccessible due to a huge reduction in possible routes. E.g. 7 years ago I could get to a large mall / parking area next to the town square maybe in 5-6 diffferent ways (allowing me to balance the traffic out).
Now there's 1 way only from my side of the city, and I can't balance anything out by going where others aren't.
Guess the "grid" street network is really a hard prerequisite.
As for safety, safety records in the city haven't moved at all in the past 10 years so I don't know. (But traffic has grown so maybe it's ok?)
Now the "best" part: Consequences if you want to drive into the city center: you need to make a sequence of correct turns 1-2 kilometers before your target, and if you don't, you are punished with extra 20 minutes in traffic at least (and still won't land where you wanted) - there is simply no route to where you wanted to go unless you pick 1 specific ideal route which many drivers don't know. Results: if you know the city / have good gps (Google Maps sometimes gets it wrong) +10 minutes in traffic, if you don't - + 20-30 minutes in traffic.
[edit] You may ask "why you can't do a triple-right-turn?" that's because the city center is not a grid. Many streets are don't have cross-paths for long stretches around historical part of the city.
Now the really painful part... Your trip outside the city center is only 5-10 minutes. Losing an EXTRA 20 minutes is a huge loss, it makes the ttrip almost as bad as walking - but inside a car. Bad for everyone really.
My main beef is with the fact that many places in the city become almost inaccessible due to a huge reduction in possible routes. E.g. 7 years ago I could get to a large mall / parking area next to the town square maybe in 5-6 diffferent ways (allowing me to balance the traffic out).
Now there's 1 way only from my side of the city, and I can't balance anything out by going where others aren't.
Guess the "grid" street network is really a hard prerequisite.
As for safety, safety records in the city haven't moved at all in the past 10 years so I don't know. (But traffic has grown so maybe it's ok?)