Hammersmith Flyover to "Flyunder"

Source: West London Link Design

The proposal to build a "flyunder," burying the A4 with a 2.3 mile road tunnel from Earls Court to the Hogarth roundabout in Chiswick, is shaping up, as the ageing and increasingly unreliable Hammersmith Flyover will need replacing, now that it is approaching the end of its lifespan. 
A "flyunder" will involve an extended tunnel being built passed the end of the current flyover, thus freeing up a large tract of land in West London for redevelopment; plus the further benefit of removing the busy A4 as a barrier between Hammersmith and the river. 
However, there is a shorter option, which would put the entrance/exit for the tunnel nearer to North End Road, thus turning that area into a major London road junction, instead of passing the Lytton Estate by and emerging at Earls Court. 
So we need to keep a close eye on developments, as the council's interim study, which will outline three alternative types of  tunnel with different lengths, is due to published later this month. 
Here are some links:

Infographic

• H&F's Flyunder page
• West London Link Design
• Boris Backs it
• The Story So Far (pdf)
• Standard story
• Construction Enquirer