I'd be interested in what the trade-offs are. I imagine space usage is a big one.
You mean to turn left, correct?
I've seen this technique used by people as an optimization. Some lights have very long wait times for left turns, so people will do what you describe rather than waiting in the left turn lane.
This design seems to shift that problem 100 meters down the road, but the challenge of crossing oncoming traffic remains (I guess without the pressure of trying to get out of a turning Yellow Light situation).
So it's definitely an improvement, but isn't there a simpler one called "Dedicated Left Turn Signals"? If both directions had an "advance left" light where both could turn safely, and there was a dedicated light for turning (i.e. no entering the intersection to turn except in a dedicated Left turn sign), this solves the problem, no?
Dedicated Turn lanes and signals need space, so they're not always possible in dense urban environments, but the Michigan setup doesn't suffer from a lack of space. So i feel like the Michigan solution is useless for San Francisco, and also not as good as the alternative for Michigan
[0] https://en.wikipedia.org/wiki/Michigan_left#/media/File:Mich...
[1] Which, incidentally, FEELS unsafe, and inexperienced drivers panic trying to get out as soon as possible, but isn't actually - these vehicles are starting from 0 and accelerating - they are unlikely to accelerate INTO you. In rushing to get out before the light turns red, they are more likely to collide with an oncoming vehicle trying to run the yellow.
Dedicated left turn light phases solve the problem too, but there's a cost to intersection throughput since there's an additional light phase (during which only left-turners on one axis can move).
There are certainly a lot of trade offs to be made here with regards to space, cost, and safety.
Pretty sure you mean 'to turn left'
These exist on major thoroughfares where the destination road is divided. So you make a right and go to the far left lane, then go into a u-turn in the median where you can make a left turn in the desired direction without worrying about crossing oncoming traffic.
Here's a link, and if you look at Telegraph Rd. just north of Maple (a few hundred yards from where Jimmy Hoffa was last seen alive), you can clearly see the traffic flow: https://www.google.com/maps/place/Telegraph+Rd+%26+W+Maple+R...