This Chapter describes the results of our individual scheme analysis. The key here is to understand the profile of demand before the 20 year mark, and after the 20 year mark, to get an understanding of what happens to demand in reality after schemes are built. The analysis suggests that demand does not stop growing after 20 years, when the current demand cap is applied.
This Chapter has the following sub-sections.
Scheme Selection – summarises how the schemes were selected.
Scheme Demand Profiles – describes the demand profiles of the schemes, before and after 20 years.
Scheme Demand Growth vs Population Growth – comments on the suitability of using forecast population growth as a predictor of demand growth.
3.1 Scheme Selection
Transport schemes were selected from those that were built 20 or more years ago, and for which time-series data was available (see Table 2). These are schemes available in our data bank and the degree to which they are representative of all transport schemes is unknown. Local major road schemes are underrepresented, for example.
Our analysis focuses on how schemes grow 20 years after opening, although the demand cap in rail tends to be applied 20 years from the appraisal year, rather than opening year, which may be five to ten years before the opening date itself.
This is primarily due to being unable to review the business cases for all of these schemes within the time frame of this study, to understand when the cap year was applied. Appendix A shows the demand profiles for each of these schemes individually with commentary on significant events and drivers of change.
Table 2 – Schemes examined in summary analysis
Scheme Opening Year Mode
A19 Barlby Junction bypass (near York) 1987 Road
A19 Billingham Diversion (near Middlesbrough) 1983 Road Dualling of A66 between Banks Gate and Bowes West 1993 Road Dartford crossing (fully connected to M25) 1986 Road
Dartford crossing (west tunnel opens) 1963 Road
M11 Motorway (fully opened) 1980 Road
M23 between Hooley and Mertsham (J7-J8) 1974 Road
M25 between Micklefield to South Mimms (J19 to J23) 1986 Road
M25 Motorway (fully opened) 1986 Road
M3 between Sunbury to Lightwater (J1 to J3) 1974 Road M40 between Stokenchurch to Waterstock (J5 to J8a) 1974 Road
M42 Southern Links (M5 to M42 J1) 1987 Road M5 between Avonmouth Bridge (J18 to J19) 1974 Road M65 between Nelson to Colne (J13 to J14) 1988 Road M74 between Millbank and Nether Abington (J12-J13) 1991 Road A616 Stocksbridge bypass (near Sheffield) 1988 Road
Docklands Light Railway (DLR) 1987 Rail
InterCity East Coast (Electrification) 1991 Rail
Glasgow Subway Re-opening 1980 Rail
Jubilee Line 1979 Rail
Manchester Metrolink 1992 Rail
Sheffield Supertran 1994 Rail
Tyne and Wear Metro 1980 Rail
Source: Arup
Some of the schemes examined have had significant capacity expansions or ridership-stimulating upgrades beyond the opening date. For example, the DLR has had numerous extensions over the years, motorway networks have been expanded, and feeder roads have changed in nature. The absence of truly unaltered schemes has made it more difficult to draw conclusions on the organic growth that schemes typically experience over the long term, however we have attempted to address this by removing a number of schemes from our sample in some of the analysis.
Some charts and tables in this section show values that ‘exclude schemes with significant further investment’, and these schemes are as described in Table 3.
Table 3 – Schemes with significant further investment
Scheme Investment
Docklands Light Railway DLR has been expanded numerous times since opening.
Jubilee Line Jubilee Line was extended in 1999
Dartford Crossing Since opening the Dartford Crossing has expanded to include a second tunnel and bridge crossing
M25 motorway Since opening there has been a series of major junction improvements and widens
Manchester Metrolink The Metrolink system has been expanded multiple times, most notably in 1999, 2002, 2014.
Source: Arup
3.2 Scheme Demand Profiles
The key point here is that demand for transport schemes tends to continue to grow 20 years after opening, as shown in Figure 16. It shows in green the median growth profile of all schemes sampled across road and rail and it demonstrates that a typical scheme tends to continue growing between their 20th and 35th year. Beyond the 35th year we have insufficient data to show clear result.
Figure 16 – Median growth profile for all schemes sampled
Source: DfT & Rail Industry Monitor 20
40 60 80 100 120 140 160 180 200
Opening year 2nd 4th 6th 8th 10th 12th 14th 16th 18th 20th 22nd 24th 26th 28th 30th 32nd 34th 36th 38th 40th 42nd 44th 46th 48th 50th 52nd 54th 56th 58th 60th
Indexed growth in passengers/traffic (100 = pax/traffic 20 years after event)
Years since transport scheme was completed
Median growth (all schemes sampled)
All projects sampled
Our analysis indicated that road and rail projects had similar growth rates once schemes that have had further significant investment were excluded. The fact that road and rail schemes have similar ‘organic’ growth profiles after 20 years could indicate that a consistent approach to growing demand in later years could be acceptable for both rail and road. Table 4 illustrates these finding with the mean outcomes.
Table 4 – Mean annual demand growth rates by age of project and mode
Y4-Y19 Y20-Y35 Y36-Y6013
All projects sampled
Road 2.5% 1.9% 0.5%
Rail 3.8% 6.1% Insufficient data
All projects sampled – excluding schemes with significant further investment14
Road 2.8% 1.3% 0.6%
Rail 1.1% 1.0% Insufficient data
Source: DfT & RIM
Note that when excluding schemes with significant further investment, we are excluding schemes which have been in high growth places.
3.3 Scheme Demand Growth vs Population Growth
We consider here whether a simple rule could be utilised as a way of forecasting long term demand growth. The rule considered is that ‘forecast population growth can be used on its own as an approximation for demand growth’.
Rationale. Using population-based growth is another approximation to considering long term demand growth, like the current demand cap
guidance. Using population growth as a tool for demand forecasting in the post-modelling period (Year 20) should only be applied if there is
certainty or evidence that this alone is what drives long term growth in demand.
Evidence. However, no evidence exists to suggest that population growth can be applied as a general rule to all schemes to forecast long term demand growth. Population growth may be an appropriate proxy for demand forecasting for certain schemes, but not for others. We know, based on our evidence from previous road and rail schemes, that for some schemes, the rate of demand growth has far outstretched the comparable rate of population growth over the same period.
The population growth forecasts also provide a limited indication as to the distribution and intensity of the growth. Our view is that an overall general approach like growing demand based on population growth isn’t appropriate.
13 We have limited data for the profile of demand for Y36-Y60.
14 Schemes excluded include: DLR, Jubilee Line, Dartford Crossing, M25 motorway and Manchester Metro Link