B&M's Centralized Manual Block: The Worst CTC

The Guilford Rail System and to some extent is predecessor Boston and Maine Railroad, had a reputation for stinginess despite being one of the more "interesting" railroads signal wise. In 2014 the formerly Guilford owned Connecticut River Main Line was restored for passenger operation that had been routed off the line in 1987 due to poor track condition.  I took a trip over this route via Amtrak's Vermonter in 2021 and posted a trip report covering the new Guilford style LED target signals, bracket masts as well as surviving instances of searchlights both in Massachusetts and on the New England Central owned portion of the line in Vermont north of the Mass border. However I missed something pretty important in that trip report that only became salient when I was processing all of the photos. Before I try and explain it I'll show a sample of the pre-rebuild Guilford Employee Timetable for the route.

At first view this looks like a pretty common Rule 261/CTC setup, an interlocking, some bi-directional intermediates.  However if you look closely you'll see that each of the two intermediates, shown at mileposts 2 and 7, are distant to the CPR-1 and CPR-9 (not pictured) respectively. That creates a rather unusual 5 mile long block in the middle of the bi-directional single track section that would be broken up by an industry standard 2-3 mile long block. Although this setup was modified in 2014, it was not modified much with a new interlocking CPR-2 eliminating the very long block with a dual distant at milepost 5 for a relocated controlled point CPR-8. The next line segment had a 6.5 mile northbound block replaced with another two 3 mile blocks with the milepost 13 intermediate.  However the third line segment is where things go off the rails again with a massive 8 mile long automatic block between the mileposts 20 and 28 intermediates.

The CT River Line changes ownership at the Massachusetts border reflecting the historic split between the Boston and Main and the Vermont Central.  No matter the ownership however, where the line had been upgraded from Track Warrant/Form D to CTC, the block lengths are reasonable, however wherever the Boston and Main had installed CTC, megablocks are the norm. In fact, on the former Boston and Maine signaled territory controlled by the NECR, the situation is even worse with the intermediate signals acting as single direction distants only similar to Amtrak's 562 cab signal territory, just without the cab signal blocks. The controlled signals in advance of the single track segments are the only indications of block status until the distant signal 2 miles short of the next interlocking. 

This creates automatic blocks of 6 miles south of Putney, 11 miles south of Bellows Falls, 10 miles south of Wapole , 14(!) miles south of Claremont and then a comparatively reasonable 6 miles south of Windsor. North of Windsor a new CTC extension has reasonably spaced blocks of about 3 miles each. At the time of my journey I figured I was just doing a bad job looking out for and photographing intermediate signals, however upon further review I wasn't missing anything, The Boston and Main had employed CTC with manual block distances and setups. If this had been the PRR they could have replaced Clear, Approach and Restricting indications at the ends of sidings with Clear Block, Caution and Permissive Block.

While this sort of layout might seem to be a clever twist of frugality, it is in fact an example of the adage "The Stingy Man Pays the Most".  Not only is the capacity not much better than with manual block/track warrant, ANY track circuit failure in ANY of these super blocks will result in a Restricting signal indication at best or, more likely, a permission past stop signal. The next choice is a 10 mile slog at Restricted speed (elapsed time 30+ minutes) or a dispatcher process to temporarily replace signal rules with TWC/DCS rules if that is even possible thanks to whatever is causing the track circuit problem, like a broken rail. This explains in part why the poor maintenance of the Guilford years formed Amtrak to move off the CT River Line and seize by eminent domain the segment between Vermon and Windsor. Any signal problem would instantly cause a 30 minute delay in addition to all the bad order track. In summary this setup might work for low density lines with some passenger trains that need better protection than track warrants. However if track circuit integrity is taken seriously, this setup is highly fragile. It's no wonder that setups such as this are somewhat more popular with axle counters substituting for track circuit integrity.