Initial note: Having read How do I design an efficient exit from a large one-way road?, the answers there do not help in this specific situation, as they rely on having lots space to spare - I have very little.
When I started my city, I designed a simple exit from the default highway that I thought was sustainable: I left enough space around it to upgrade the road as I needed to, which has worked up until now. However, I am now stuck with a six-lane one-way exit from the highway that isn't getting used: since cars seem to pick the most efficient lane to get where they want to go, regardless of traffic, the rightmost lane fills up, then spills over onto the highway. This blocks the highway, my bus routes, and more importantly my planned emergency routes.
My setup looks like this:
The red arrows show road direction, and the orange line is the traffic backed up. Note that in this image, I have replaced the six-lane one-way exit with a highway exit, as this is just about as efficient...
This situation is getting to be pretty bad, and is bringing half my city to a standstill. Its effects compound themselves further down the highway:
In this image, the orange line is the traffic directly caused by this exit not working. This traffic jam then blocks two exits/entrances further down, on the red crosses; the yellow line shows the traffic jam caused by these being blocked. In other words, my inefficient exit design is now blocking itself from moving.
So this is a two part problem.
Considering that I'm constructing a residential district in the space above left of the problem exit, and would like to keep the solution inside the power line, how can I redesign this exit to be more efficient?
How do I solve the ring of traffic jams? Is it a simple case of just deleting and replacing a bit of road?