Route carryings and capacity utilisation

Carryings

In order to provide context for the capacity utilisation analysis, there is benefit in setting out the aggregate trend for each route in terms of carryings – this should be built-up from published data sources such as Scottish Transport Statistics and sailing-by-sailing data over a circa ten-year period. The following indicators have been developed in relation to carryings, with the required data shown in italics below:

  • How have passenger and vehicle carryings changed over time?
    • 10-year time series (a longer time-series could be used where appropriate, for example where a new vessel was introduced at or just before the start of the 10-year period).
    • Presented in absolute terms and indexed to e.g., 2013.
    • For routes on the CHFS network, a statement of the year in which Road Equivalent Tariff was introduced should be provided.
  • How have coach and commercial vehicle (CV) carryings (absolute numbers and lane metres) changed over time?
    • 10-year time series (a longer time series could be used where appropriate).
    • Presented in absolute terms and indexed to e.g., 2013.
    • Ideally these data would also disaggregate motorhomes – some CFL datasets do provide this and should be obtained if possible.
  • How do passenger and car carryings vary across the year?
    • Monthly carryings statistics for the most recent year.
    • Ratio of ‘deep’ winter (i.e., November to February inclusive) to peak summer (i.e., July and August) carryings for cars, CVs and coaches.
  • How do passenger and car carryings vary by day of the week?
    • Sailing-by-sailing data for the most recent calendar year used to calculate % travel by day of the week.
    • Carryings should be shown separately for each direction to pick-up peak travel days.
    • Ratio of vehicles to passengers.

Capacity utilisation

The ability to secure a vehicle booking (and cabin booking on SNF) on the ferry is an issue of primary concern for many island residents and businesses. The passenger certificate of most vessels means that passenger capacity is rarely a problem on most routes, although there are isolated sailings which are fully booked. It is therefore important that detailed analysis of vehicle-deck capacity utilisation is undertaken (analysis of passenger utilisation can be undertaken where it adds value). 

That said, the analysis undertaken needs to be proportionate to the extent of the potential problem – on some routes, vehicle-deck capacity will:

  • Rarely, if ever, be a problem.
  • Be concentrated in a specific season – on most routes, this will be in summer but the reduction in services in the winter timetable, vessel redeployment during drydock periods or winter operating restrictions does cause capacity issues on some routes.
  • Be concentrated on a specific sailing or day.
  • Be a problem on most sailings.

Vehicle-deck utilisation

Vehicle-deck utilisation is the main area of interest from a capacity perspective, as it is the component of capacity which is most frequently under pressure on ferry services throughout Scotland. Ideally, the analysis would be split by periods of:

  • Normal timetabled operations.
  • Disruption (requiring a cross-reference with the performance data introduced above).

However, vehicle deck utilisation is currently difficult to calculate precisely. Note, on the Clyde and Hebrides network, outputs from the new booking system – Ar Turas – may simplify the process of calculating vehicle deck utilisation. If this is the case, this guidance paper will be updated at the appropriate juncture. The current data are complex and inexact, as e.g., on the CHFS network:

  • Reported carryings data records only ‘cars’ plus CVs / CV lane metres and coaches / coach lane metres - ‘cars’ includes vans, some campervans, trailers, caravans etc, so ‘Car lane metres (LM)’ are not known and have to be estimated.
  • Wider vehicles can straddle two lanes, leading to dead space on the vehicle deck. A sailing may therefore appear to have deck space from an LM perspective, but this deck space cannot be used.
  • Deployment or otherwise of mezzanine decks affects total lane metre capacity and is not systematically recorded – this can sometimes be inferred from the data though.
  • Report vessel carrying capacity has been eroded as vehicles get larger.
  • Whilst a diminishing problem as vessels are gradually replaced, vessel deadweight limitations can also be an issue. In such instances, the vehicle deck may not be full in terms of LM usage but, because a weight threshold has been reached, no other vehicles can be carried.
  • Attempted but failed bookings, stand-by lists etc. are not systematically recorded so any suppressed demand is not known.

Acknowledging the above caveats, it is possible to build-up analysis of estimated vehicle deck utilisation (load factors) from sailing-by-sailing data. The following indicators have been developed in relation to carryings, with the required data shown in italics below:

  • How much capacity is there across the year?
    • Aggregate figures showing the proportion of sailings within set load factor bandings of <25%, 25%-50%, 50%-75%, 75%-90%, >90% across the year, by season etc. This can be for all sailings or by individual sailing (e.g., the weekday 07:00 departure from Stornoway).
    • Development of a ‘loadings calendar’ (or equivalent) showing load factors for each day of the year (within set bandings of <25%, 25%-50%, 50%-75%, 75%-90%, >90%) by direction for every day of the year. These can be set up to show maximum, mean, median or total daily load factors or load factors on any specific sailing and can be tailored to the route in question.
    • This can be for the most recent calendar year or for a longer time series, as appropriate for the route in question.
  • How often is capacity a problem?
    • Development of ‘box and whisker’ load factor charts – these can be by month, season, week, day and / or sailing.
    • This can be for the most recent calendar year or for a longer time series, as appropriate for the route in question.

Passenger utilisation

Passenger utilisation is fairly straightforward to calculate – i.e., it is the passenger carryings on any individual sailing as a proportion of the vessel’s passenger certification and / or maximum passenger capacity for that sailing where variable passenger certificates are used. Equivalent indicators to those developed for vehicle deck utilisation could be developed for passenger utilisation. However, in the interests of proportionality, it is recommended that effort is targeted at routes and / or individual sailings where this is understood to be a problem, which are currently relatively few and far between.

Cabin utilisation

Equivalent analysis could also be undertaken with regards to cabin and sleeping pod utilisation on SNF sailings. It should though be noted that the analysis will show the number of cabins booked as a proportion of the total, which is one measure of utilisation. However, it is common on SNF services for the cabins themselves to be under-utilised (e.g., a four-berth inside cabin booked by a single occupant) and the data will not readily capture this, although the discontinuation of shared cabins makes this less of an issue than it once was.

The output of this step will be a clear set of current route performance metrics which will provide some quantification of how well the service is meeting the needs of the island in terms of reliability, punctuality and the ability to travel with a vehicle and / or secure sole occupancy accommodation when travelling on SNF.