Timetable: Technical Overview
The December 2007 timetable commenced operation on 9 December and continues until 17 May 2008.
Services on the Far North Line are retimed although the structure of the service pattern remains the same as previously.
The building blocks for each individual train schedule include:
- Sectional Running Times (SRTs) the time between stations, junctions etc
- Dwell Times (time when a train is at stationary either at a station or signal)
- Other allowances which include:
- performance time - additional time inserted into the schedule at key points to give right time presentation of the train at junctions, terminal stations;
- engineering allowance - additional time to offset temporary speed restrictions and/or other engineering activity en route that results in extended SRTs or dwell times;
- pathing time - added to schedules to path a train at given headway and junction margins;
- public differentials - time added at the end of a journey to give a later advertised time in the public timetable, or time subtracted where departure times are advertised in advance i.e. advertised in the public timetable earlier compared to the Working Timetable.
Not all these allowances are applicable on the Far North Line. However, four minutes 'engineering allowance' is added to individual Far North Line schedules split two x 2 minutes. These are added to the schedules at the following locations:
Northbound - 2 minutes approaching Lairg and 2 minutes approaching Georgemas Junction;
Southbound - 2 minutes approaching Lairg and 2 minutes approaching Dingwall. (note the occasions when you arrive at Lairg early and have to wait for right time departure).
Whilst these allowances are shown in the Working Timetable as engineering allowance, they also act as performance time. In some cases they can double up as pathing time and some degree of flexibility is used as to the positioning of the allowance. Put simply, where previously engineering allowances have been added to schedules at Forsinard (in the 1237 ex Wick) or Tain (1552 ex Wick) these have now been redistributed appropriately to Lairg and Dingwall respectively. Hence why the 1237 ex Wick is 2 minutes later throughout from Lairg and the 1552 ex Wick 2 minutes earlier at Tain and therefore the 1753 ex Inverness retimed 1 minute earlier from Inverness and 2 minutes from Tain. These may be only cosmetic changes that theoretically improve PPM by a small percentage point but nevertheless represent the building blocks of the timetable.
However, applying the above principles we now have the 0635 ex Lairg retimed earlier throughout for two reasons: (i) to allow for 2 minutes engineering allowance to be inserted at Dingwall and (ii) to increase the dwell time at Dingwall to provide a robust, reliable, right time crossing with the 0714 ex Inverness. This means that for passengers joining the train at Tain, Fearn, Invergordon and Alness they have a journey time extension of 4 minutes on the morning commute to work. Also, the 1033, 1312 and 1531 Invergordon - Inverness services have had 2 minutes engineering allowance added approaching Dingwall. This is arguably excessive, considering the best overall (assuming best clean path) journey time of 48 minutes (31½ miles) between Invergordon and Inverness. Good performance is not all about making journey times longer - it is getting the small, attention to detail basics correct. Regrettably, the FNL still suffers from poor performance due to fleet reliability issues where 2 additional minutes in the schedule can make no difference.
The reliability (strictly speaking punctuality as the train runs, albeit late) of the commuter service in the evening doesn't add confidence to regular passengers. Often a late start (due to the inward working being late and train crew diagrammed for a PNB), the 1752 ex Inverness will be held at Invergordon adding further delay minutes to Tain commuters. Insult is added to injury as some passengers have to stand which is in itself not unreasonable (the National Carriage of Conditions does not guarantee a passenger a seat) but when there is an empty two car set attached to the same train in which they are standing, this is unacceptable, particularly at times of excess passenger loadings. Nevertheless, this is an interim problem as it is planned, from the December 2008 timetable, that the 1752 departure will be a 4 car train to Dingwall with the front portion for Wick and the rear portion for Kyle of Lochalsh. FoFNL is working with FSR and Transport Scotland in developing a 'win-win' solution as the status quo is not acceptable for the next 12 months.