Transport Forecasts and Self Fulfilling Prophesies

In November 2018 Transport Scotland published their first transport demand forecasts. In the past reliance was made on the forecasts published by the Department for Transport in London. Transport Scotland say that the main purpose of publishing these forecasts is to “report the transport forecasts generated by the Transport Model for Scotland (TMfS) and the Transport and Economic Land use Model of Scotland (TELMoS).”
Transport Scotland say “The forecasts are not self-fulfilling; i.e. the exogenous assumptions and agreed interventions from which this baseline was developed will change.” This is a slightly strange statement since the fact that the exogenous assumptions and interventions change does not imply that the forecasts are not self fulfilling. However throughout the document there are many health warnings and requests to contact Transport Scotland if users are unsure.
The forecasts explain that there is uncertainty associated with many factors. In Chapter Four, outputs from sensitivity tests are described to understand the sensitivity of the model to some of the more influential assumptions; population, economic growth, fuel prices and car ownership.
Do we still need transport forecasts? These are published as model results so is that a more helpful way to explain them rather than forecasts?
What other steps need to be taken to help to develop robust transport plans in a changing world?
Contribute to the STSG transport planning and forecasting debate here.

1 Comment

  • The 42 page document (available on TS website) was published in mid-November. It contains initial forecasts from 2014 to 2037 and initial assumptions on population and land use changes

    Initial Transport Scotland assumptions 2014-37
    6.5% rise in population
    25% rise in person trips by car
    7% fall in urban bus passenger miles
    44% rise in road vehicle goods trips
    5% fall in inter-urban bus passenger miles
    40% rise in road vehicle miles (to 28 bn)
    42% rise in rail passenger miles

    NOTE also no detail given for total personal miles by car (taking account of occupancy & length of trip) and no detail given for tonne miles moved by road, including load factors and length of trip)

    Total passenger miles
    Year, Urban Bus, Inter-urban Bus, Rail
    2014, 236m, 1,320m, 2,400m
    2022, 233m, 1,280m, 2,840m
    2027, 227m, 1,280m, 3,030m
    2037 220m 1,250m 3,400m

    No data provided on walking, cycling, taxis/private hire, ferries, ports and rail freight. Other data suggests that the rise in cycle miles may be well over 100% though with strong focus on shorter trips. No data given on average length of personal car and goods trips by road – is this expected to rise or fall? What changes are expected in levels of car occupancy?

    No data on Glasgow Subway, Edinburgh trams and other heritage or mountain rail trips or on rise and nature of cruise shipping and private cruising/passenger only ferries to, from and within Scotland

    No data provided on passenger miles by car (including occupancy levels and assumptions on changes in average length of trips) – yet there are prospects that the average length of trips by car may fall partly compensated by improved occupancy, especially at urban peaks, and some further shifts to cycling)

    No data on pass. miles by air a) beyond UK b) between Scotland and rest of UK c) within Scotland
    Average road vehicle delays per mile expected to rise from 1 minute 29 sec to 1 min 40 sec. with PM peak delays up from 29.3 sec to 57.1sec.

    Fares peak Rail Fares and all Bus, Ferry, Subway Fares and Parking Charges up at RPI (but with off-peak rail fares up by RPI -1% to 2021). No mention of levels of Road Fuel duty or variable road and parking charging
    Transport Infrastructure Assumptions 2027 (p30)

    17 road schemes scheduled for completion by 2017 but several are still uncompleted (no mention of any on
    A9 or any major work on A96) 3 road schemes listed for completion by 2022 (Inverness west link, Tay crossing at Perth, M8 Bishopton Jc) and 1 for 2027 (M8 Winchburgh Jc)

    5 rail schemes listed for completion by 2017 (all still uncompleted or not started) Aberdeen-Inverness Rail, Perth-Inverness Rail, EGIP, Carstairs improvements, 4 extra services per hour on Glasgow-Paisley line

    Land Use Assumptions Volume of allocated land for housing and other development is outlined but not the issue of how far this land is allocated in ways supportive of government policies for low carbon sustainable development, shifts away from car use, equitable access and improvements in air quality and local environments

    Forecasts for Eight Areas within Scotland
    These are presented separately for road vehicle miles, bus passenger miles and rail passenger miles rather than as regional overviews of movement and modal share – and related volumes to and from other regions. Road traffic growth above 40% to 2037 is forecast for North-east (boosted by AWPR) with Ayrshires having the lowest growth at 30%. Only the North-east, DG and Highlands/Moray are forecast to have (very modest) growth in bus passenger miles. Regions with rail passenger miles up more than 40% by 2037 are North-east, SESplan, GCV and Stir/Clack/Fal

    Next Steps
    ‘Transport Scotland initial forecasts are based on current travel behaviour and committed transport schemes (they also assume continuation of the present fiscal, pricing and regulatory framework – including land use policies). The NTS review will go further and set out an updated vision of what kind of transport (and access?) system we want for the whole of Scotland over the next 20 years and how we plan to get there’. 168 factors affecting future travel demand were identified in 2017 and these are being further studied and refined as part of Scenarios for Probable, Plausible and Possible Futures.

    COMMENT
    Though with clear recognition of a continuation of the rise in the rail modal share of passenger movement which began around 2000 in Scotland (and in UK), this Transport Scotland document is still heavily influenced by a preoccupation with modelling road traffic growth (and identifying points of rising congestion) rather than looking at overall views on how transport and access is likely to change in an economy which will be stronger, more sustainable with low carbon targets and also aims for a more equitable and inclusive society with improved health and local environments – and possibly a higher rate of population growth than in present estimates.

    There is a surprising lack of reference to tourism growth (and its possible implications) and no explanation of why growth in goods vehicle road trips is so high – with no mention at all of freight by rail and water – is this mainly light van growth or heavier lorries? – why is rail freight not mentioned especially in relation to longer and bulk hauls? Why is there no mention of cycling or walking? This is the first official publication to mention passenger miles by bus and confirms what has been suspected for some time i.e. that passenger miles by rail are already higher than by bus. A definition of ‘urban bus’ is needed, also a category to indicate rural travel by bus and recent changes in taxi, private hire and other alternatives for shorter distance rural trips linking well with key longer distance public transport by both rail and bus. Why is there no mention of major A9 and A96 schemes while including Perth-Inverness and Aberdeen-Inverness rail improvements (possibly due to no firm funding commitments though with high spend on design work)?

    The emphasis on modes needs to be replaced by more integrated yet subdivided information on transport and access e.g data on changing nature of movement to and from Scotland
    Volume and modal share of trips crossing regional boundaries within Scotland
    Trips and the modes used within regional bounds
    Quality of interchanges, frequency preferences and simplified integrated ticketing

    The prime need is a change of emphasis from the assumption that present arrangements for fiscal, pricing and regulatory policies have a good relationship with wider, and stated, government objectives. This should be crucial in phased reforms in a National Strategy for Transport and Access also contributing to a stronger, more inclusive and sustainable economy. Strategy needs to highlight the aim, and impact, of a major review fiscal, pricing and regulatory practices by 2025.

    Subject to further evaluation and five-yearly reviews, this could lead to 2037 outcomes of :-

    10% rise in population to 2037 but a slowing of growth rate in air travel
    20% fall in person travel by car (modest in dispersed areas but higher in, and between, cities)
    30% rise in road goods vehicle miles (but larger rise in rail/shipping freight)
    30% rise in walking and 150% rise in miles cycled per year (mainly shorter-distance)
    70% rise in rural/smaller town bus/DRT use but a 150% rise in city area public transport use
    (including city related rail/light rail trips less than 20km in length)
    150% rise in longer-distance rail passenger miles within and to and from Scotland
    80% cut in transport carbon and local pollution related to trips internal to Scotland (but a lesser
    reduction for external movement by air and shipping modes)

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