The Far North Line: Inverness - Dingwall Line Capacity
The distance from Inverness to Dingwall is 18.58 miles. There are two intermediate stations at Beauly (reopened in 2002) and Muir of Ord (reopened in 1976)
Although only 2.3 miles from Dingwall, it is now proposed to reopen a third station at Conon Bridge in order to gain local traffic to and from Inverness. Provision has already been made in the running times of trains between Inverness and Dingwall for this stop to be introduced when funding has been secured.
At present there are two single line sections between Inverness and Dingwall:
Ness Viaduct to Muir of Ord 12 miles 24 chains
Muir of Ord to Dingwall 5 miles 24 chains.
At present, there is one intermediate station between Inverness and Muir of Ord. The addition of Conon Bridge will add a station in the short section between Muir of Ord and Dingwall.
Although there is a 42 chain loop at Muir of Ord, the present timetable makes use of this facility only twice on weekdays and once on Sundays. Clearly the loop is also available at all times to pass trains that are running out of course but no information is available on how often it is used for this purpose.
FoFNL has proposed that an additional loop be provided between Lentran (5 miles 78 chains) and Clunes (7 miles 69 chains) in order to provide extra capacity on the line between Ness Junction and Muir of Ord and to give additional operational flexibility to reduce additional delay when trains are running late.
Before addressing these capacity and reliability issues, it is important to understand how an additional loop would fit into the overall infrastructure between Inverness and Dingwall. The first important point to recognise is that current capacity is severely constrained for the following reasons:
- 15 MPH speed restriction from the platforms to Rose St Junc and the 20 MPH from there to single line junction
- 10 MPH over Clachnaharry Swing bridge
- 35 MPH Bunchrew AOCL
- 15 MPH through both ends of the Muir of Ord loop points
- 50 MPH over Conon viaduct
- 15 MPH over the loop points in to Dingwall
The second point to recognise is that the proposed loop would be inserted into the first 75 MPH section of line from Inverness. The third point is that, until the RETB signalling is replaced, the new loop would result in two additional 15 MPH speed restrictions (i.e. at each end of the loop) on what is now a 75 MPH section of line. In other words, all trains would need yet another increase in journey time of 2-3 minutes (two 15 mph restrictions 40 chains apart on a 75 mph section).
In a paper, "Strengthening of the Far North Line" (June 2009), the proposed double track section is described a dynamic loop but of course it cannot be because of the short distance. Even if the route was re signalled with track circuit block and 75 MPH turnouts installed it would not be possible to path two trains to pass at line speed over such a short section.
It follows that the proposed loop between Lentran and Clunes will disadvantage more trains than it can benefit with existing signalling. The work undertaken by Gavin Sinclair, Secretary, demonstrates that capacity can be increased within the existing infrastructure by introduction of an even interval pattern without an additional loop.
I have examined the reliability and punctuality statistics for the ScotRail Highland Group, (which includes the FNL trains) for the last 12 months. These show that 99.3 % of the trains ran and that 95.2% arrived within 10 minutes. With figures like this, the case for an expenditure of several million pounds for the Lentran loop with negative journey time and capacity benefits seems impossible to make.
In conclusion, I believe that the FoFNL should as a matter of priority press for journey time improvements, particularly over the key revenue earning section from Inverness to Tain/Lairg