Agreed, it's pretty bad. I have taken to changing lanes from the bike lane to the vehicular travel lane a few hundred feet before the end of the bridge (although it's tough to go between the flexposts at high speed, but it is doable) to avoid the risk of Something Bad happening at island.

I gather TP&T was consulted on this design and approved it? What is the thinking? also, there is an SCF issue with a photo of the problem that helps to understand this...

https://seeclickfix.com/issues/4517112-pavement-marking-issue

I'm confused why that was closed and sent to MassDOT with such optimism. Let me mark up the photo to show it a little better...it's hard to make the (1)-(2) transition at speed, and totally impossible to do (2)-(3).

If the goal is to slow down bikes, it's effective, but it's TOO effective. It makes us leave the bike lane and do something that's probably more dangerous.

The bend also makes it harder to look over your shoulder for approaching cars. Even at slow speeds this configuration makes no sense to me. It seems like it’s asking for conflicts and crashes.

It is not possible to safely allow a conflict between turning vehicles and through bicycles while either road user is moving at a high rate of speed. The turning island requires both turning vehicles and through bicycles to reduce their speed on approach to the intersection. MassDOT will be installing additional signage to increase the visibility of the island and reinforce the requirement for turning vehicles to yield to bicycles.

The only way for a cyclist to safely travel through the intersection at the high speed created by the downhill approach is to use the through vehicle lane.

If you want some indications that signs won't solve problems, go watch the speed limit sign on the bridge. It says 25MPH, but I regularly see drivers going 35, 40, 45MPH on this bridge. A yield sign isn't going to prevent collisions, but a better designed intersection might.

Couterargument::
> go watch the speed limit sign on the bridge. It says 25MPH, but I regularly see drivers going 35, 40, 45MPH

Is the speed limit posted anywhere other than in the middle of the bridge? I haven't seen it posted at the ends, so it does seem kind of a bit of a trap?

The city wide speed limits in both Boston and Cambridge are 25MPH. So, you really shouldn't have any reason to think that the bridge is anything else. Also, do you really think all these drivers are making their inaugural trip over the bridge? The first time over it, you'll see the sign.