reaperexpress
Senior Member
The existing tunnel has a speed restriction due to low clearance. Reducing it to 2 tracks will eliminate the speed restriction.Not sure why they are going that far east as the 4-track interlock block is a short distance to the east of Islington with all four tracks in place with block working signals. There is enough room from the interlock to Islington to spread the tracks apart for two tracks to use the two tunnels and two of the three tracks currently under Islington Overpass. Since you already had three tracks under Islington, I found it odd that they need to build two extra tracks under the 401/409 unless they were looking at having five tracks at this point to the airport cut off with two being used for UPX only.
There is not enough space for 4 tracks under Islington with the existing grading. They need to build a retaining wall on the south side of the underpass to fit the south track under the existing structure.
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