More than you ever wanted to know about my model railroad
This map shows how the PV&T climbs out of the Connecticut River valley into Vermont. This is the incline that makes the Madison incline in Indiana not look quite so spectacular.
The blue line with the red rectangles is the original PV&T line from Thetford to Strafford (not shown) When it was built in 1856, the railroad decided to use rope-hauled inclines (red boxes) to get cars over Thetford Hill. By 1875, this was a huge bottleneck, and the PV&T built a new line (yellow line) with a tunnel (black box) at 730' ASL, which reduced the grade from the east to 8000 feet of 4.1% grade, and from the west to a little over a 1% grade.
It took about a year to cut the tunnel, and the new line was put into service in 1877. The inclines were kept in reserve until 1880, when the winding engines were taken out of service (the inclines themselves were never dismantled; the approach to the east incline was removed in the 1920s because the state of Vermont wanted to use the right-of-way for a highway relocation, but the inclines themselves are still visible if you look carefully enough.) The tunnel is graded up from both ends to the center, and a large ventilation shaft was drilled down just west of Thetford (approximately where the east incline winding engine was located) and fitted with large fans to suck exhaust fumes out of the tunnel.
After the PV&T got trackage rights into Montréal, PQ, the Thetford bottleneck (and the Lyme, NH to Ashland, NH bottleneck, but that's a different story) slowly came back. The PV&T was one of the shortest routes between Portland and Montréal, so bridge traffic split pretty evenly between it and the Grand Trunk, but to get trains over the interesting Strafford to Ashland division took lots and lots of helper engines. By the turn of the 20th century, the PV&T had 12 helper engines stationed at East Thetford, 4 helper engines stationed east of Strafford, and 12 helper engines stationed at Ashland, NH, and these engines were becoming woefully inadequate for the job. In 1904, a large collection of decapods were ordered, but by the time they started to arrive traffic had jumped again to the point where they weren't sufficient for the job.
What was left for a railroad to do? But that's another story.
