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Chapter Six Understanding trends in long distance commuting
Introduction
6.1. Consideration is now given to the historic trends in Scottish long distance commuting. The key sources of data utilised in the analysis were as follows:
- The National Travel Survey (to provide a GB-wide context)
- 1991 and 2001 Scottish Census travel to work data
- The SHS data (covering 1999 to 2005)
- TMfS forecasts
6.2. Initially NTS, Census and SHS data was used to explore historical trends in long distance commuting. Results from the Transport Model for Scotland ( TMfS) were then used to analyse the TMfS forecasts of future long distance commuting in Scotland.
National Travel Survey trends
6.3. The National Travel Survey is a key source in examining long distance commuting trends. The 2004 National Travel Survey (2005 Transport Statistics, Department for Transport) shows changes in personal travel over the previous decade and includes trends in distance, number of trips and time spent in travelling.
6.4. Between 1992/1994 and 2004, commuting trip rates decreased by 7% from 158 trips per person per year to 148 trips per person per year (see Table 6.1). Since 1992/1994 there has been an increase of 15% in the number of escort education trips (trips solely to take another person whose trip is education) and 45% increase in annual miles per person for this journey purpose.
6.5. The average length of commuting trips increased by 13%, education trips increased by 8% and escort education trips by 25% (Table 6.1). The average time of a commuting trip increased by 8%, educational trip time increased by 11% and escorted educational trips by 8% (Table 6.2)
Table 6.1: NTS ( GB) average trip length (kilometres) per person
Year | Commuting | Education | Escort education | All purposes |
|---|
1992/ 1994 | 12.1 | 4.5 | 2.9 | 9.8 |
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1998/ 2000 | 13.5 | 4.7 | 3.2 | 10.6 |
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2002 | 13.7 | 5.1 | 3.7 | 10.9 |
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2003 | 13.7 | 4.8 | 3.4 | 11.1 |
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2004 | 13.7 | 4.8 | 3.5 | 10.9 |
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Table 6.2: NTS ( GB) average trip time (minutes) per person
Year | Commuting | Education | Escort education | All purposes |
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1992/ 1994 | 24 | 18 | 12 | 20.5 |
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1998/ 2000 | 24 | 19 | 12 | 21.0 |
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2002 | 25 | 20 | 13 | 21.6 |
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2003 | 26 | 20 | 13 | 21.9 |
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2004 | 26 | 20 | 13 | 22.0 |
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Geographic comparison of 1991 and 2001 census travel to work data
Introduction
6.6. Geographic comparison of 1991 and 2001 Census travel to work data were undertaken to determine possible variations in the growth of long distance commuting within Scotland.
6.7. The 1991 Census data is confined to employed and self employed people and does not include those in education. The 1991 set provides the journey to work flows within and between postcode sectors in Scotland. The procedure described in Chapter 3 was followed for English cross-border travel to workplaces.
6.8. Initial data processing was carried out to make the 1991 and 2001 Census travel to work data compatible. This was achieved by aggregating the 2001 output areas into 1991 Census postcode sectors. Road-based distances between each postcode sector were then estimated from the Ordnance Survey road network using a Geographic Information System ( GIS). (Note: Previous 2001 road based estimates were based on data zones and not postcode sectors. Consequently, 2001 results presented in this section may differ slightly from those stated elsewhere in this report).
6.9. Initial comparisons of the 1991 and 2001 Census datasets indicate slight increases in average commuting distance and percentages of long distance commuting. In 1991, 26.0% of out-commuting trips were long distance (greater than 15km). In 2001, 26.7% of out-commuting trips were long distance. This represents a 2.7% increase in the percentage of long distance commuting over the decade.
6.10. In 1991 the average commuting distance was 11.95km (N=179,790). In 2001, the average commuting distance had increased to 12.50km (N=2,136,549). Average commuting distance in 1991 and 2001 for residents of each Regional Transport Partnership are shown on Figure 6.1. As may be seen, Highlands and Islands (17% increase), Central and Tay (7%) and South West (6%) have had a relatively high increase in the average commuting length between 1991 and 2001. In contrast, Shetland (13% decrease) had a relatively large decrease in average commuting distance.
Geographic comparison of 1991 and 2001 Census travel to work data for Local Authorities
6.11. This section considers the changes in the distribution of long distance in-commuting and out-commuting by Local Authority area. The percentage changes in long distance commuting between 1991 and 2001 are provided by Local Authority in Annex 2. The results are displayed in map form on Figure 6.2 and Figure 6.3.
6.12. The figures illustrate the change in percentage long distance commuting (% LDC). The change in percentage long distance commuting was estimated as follows:
Change in % LDC between 1991 and 2001 = [% LDC (2001) - % LDC (1991)]/ % LDC (1991).
6.13. As may be seen, Aberdeen City (22%), Dundee City (20%), West Dunbartonshire (17%), Glasgow City (13%) and Clackmannanshire (13%) have had a relatively high increase in their long distance out-commuting percentages between 1991 and 2001. In contrast, Orkney Islands (-29%) and Eilean Siar (-29%) have had a relatively large decrease in their long distance out-commuting.
6.14. Clackmannanshire (28%), West Lothian (26%), Aberdeen City (23%), Midlothian (21%) and Moray (20%) have seen relatively high increases in their long distance in-commuting between 1991 and 2001. In contrast, Orkney Islands (-25%) and Eilean Siar (-25%) have seen a relatively large decrease in the percentage long distance in-commuting.
Geographic comparison of 1991 and 2001 Census travel to work data by mode share
6.15. An analysis of Census data (1991 and 2001) was undertaken to determine percentage changes of long distance commuting by method of travel for Scotland. Figure 6.4 details mode share by year. It may be seen from Figure 6.4 that between 1991 and 2001, long distance commuting mode share for car drivers has increased from 66% to 71%. Over the decade, train commuters mode share has increased from 6% to 7%. During the same period, mode share for bus long distance commuters has decreased by almost a third (12% to 8%). In addition, car passenger mode share has decreased significantly from 11% to 8%.
6.16. The following additional information detailing mode share by Local Authority is provided in Annex 2:
- In-commuters: Mode share percentages by Local Authority (Census 1991)
- Out-commuters: Mode share percentages by Local Authority (Census 1991)
- In-commuters: Mode share percentages by Local Authority (Census 2001)
- Out-commuters: Mode share percentages by Local Authority (Census 2001)
- In-commuters: Change in percentage mode share (Census 1991 to 2001) by Local Authority
- Out-commuters: Change in percentage mode share (Census 1991 to 2001) by Local Authority
Geographic comparison of 1991 and 2001 Census travel to work data for car drivers
6.17. Within this section, consideration was given to the historic trends (Census 1991 to 2001) in car driver mode share of long distance commuting. The percentage changes in car driver mode share by Local Authority for out-commuters are shown on Figure 6.5 and in-commuters are shown on Figure 6.6.
6.18. West Lothian (19%), Scottish Borders (16%), Eilean Siar (15%) and Falkirk (15%) have produced a relatively high percentage increase in long distance car mode share between 1991 and 2001. In contrast, Aberdeen City (-3%) and East Renfrewshire (-2%) have seen a decrease in long distance car driver mode share.
6.19. Argyll and Bute (25%), East Lothian (24%), Scottish Borders (19%) and Eilean Siar (17%) have attracted a relatively high increase in long distance car driver mode share between 1991 and 2001. In contrast, Aberdeen City (-10%) has seen a decrease in long distance car driver mode share.
Analysis of SHS commuting trip-length data
6.20. Analysis of SHS commuting trip-length data (February 1999 to March 2005) was undertaken to determine whether or not there had been statistically-significant increase in commuting trip-length or percentages of long distance commuting. Figure 6.7 suggests that there has been no significant growth in the proportion long distance commuting for each of the thresholds for long distance recorded via the Scottish Household Survey.
Comparison of Census, NTS and SHS historic trends
6.21. Figure 6.8 illustrates historic trends over time for Census, NTS (Scotland) and SHS data. Generally the data sources indicate growth in long distance commuting in the 80's and early 90's, levelling off recently. It is noted that:
- National Travel Survey ( NTS) results for Scotland indicate that there was steady growth in average commuting distance in the 1980s and early 1990s (20% increase between 1985/86 and 1992/94), but this may now have levelled off, or started to decrease. Results indicate a slight decrease in average commuting distance between 1995 and 2003 (1% decrease between 1995/97 to 2002/2003). The apparent slight decrease could well be the result of sampling variability
- The NTS estimate of growth in average commuting distance between 1991 and 2001 is higher than the estimation from the Census
- The SHS data suggests a slight decline in average commuting distance since 1999 (4% decrease between 1999 and 2005)
Census historic trends and TMfS predicted trends
6.22. TMfS forecasts small growth (0.3% per year) in the percentage of car long distance commuters, as a percentage of total car trips, over the next 10 years. This is broadly consistent with the recent historic trend (ie growth in the 80's and early 90's, levelling off recently). Figure 6.9 illustrates the predicted growth in car long distance commuting. It should be noted that TMfS based estimates exclude intra-zonal trips which lead to its slightly higher estimates of long distance car driver commuting.
Analysis of TMfS forecasts of future travel-to-work trip length distributions
6.23. The existing Transport Model for Scotland ( TMfS) networks for the base year (2002) and future years (2006 and 2011) were used to predict future AM Peak travel to work trip length distributions. The infrastructure and land use assumptions were those within the current TMfS reference case (2002).
6.24. Overall, TMfS predicted that the number of long distance commuter trips would increase by 20% between 2002 and 2011.
6.25. There were a number of regional differences within the predicted increases between 2002 and 2011. The largest percentage increase for long distance out-commuters were for residents of Glasgow (90%), Aberdeen (54%), West Dunbartonshire (35%) and Dundee City (33%). Figure 6.10 details the predicted percentage changes in the number of long distance commuters living in each Local Authority.
6.26. Figure 6.11 shows the predicted percentage increase in the number long distance in- commuting for each Local Authority. The largest predicted percentage increases are for Midlothian (55%) Edinburgh (50%), East Renfrewshire (42%) and Renfrewshire (41%). Figure 6.12 and Figure 6.13 show the change in absolute numbers of in-commuters and out commuters.
6.27. Figure 6.14 and Figure 6.15 shows the corresponding percentage increase in the number of long distance out-commuting and in-commuting for each Regional Transport Partnership.
Figure 6.1: The percentage change in long distance out-commuting between 1991 and 2001 by Regional Transport Partnership
Figure 6.2: The percentage change in long distance out-commuting between 1991 and 2001 by Local Authority
Figure 6.3: The percentage change in long distance in-commuting between 1991 and 2001 by Local Authority
Figure 6.4: Long distance mode share (Scottish Census 1991 and 2001)
Figure 6.5: Percentage change in car driver mode share by Local Authority for long distance out-commuters
Figure 6.6: Percentage change in car driver mode share by Local Authority for long distance in-commuters
Figure 6.7: SHS Commuting Trips (February 1999 to March 2005)
Figure 6.8: Average commuting distance by year ( NTS, Census and SHS data)
Figure 6.9: Census historic trends and TMfS predicted trends
Figure 6.10: Changes in percentage of long distance out-commuters by Local Authority (only those in the area covered by TMfS)
Figure 6.11: Changes in percentage of long distance in-commuters by Local Authority (only those in the area covered by TMfS)
Figure 6.12: Changes in absolute numbers of long distance out-commuters by Local Authority (only those in the area covered by TMfS)
Figure 6.13: Changes in absolute numbers of long distance in-commuters by Local Authority (only those in the area covered by TMfS)
Figure 6.14: Changes in percentage of long distance out-commuters by Regional Transport Partnership (only those in the area covered by TMfS)
Figure 6.15: Average commuting distance in 1991 and 2001 for out-commuters by each Regional Transport Partnership
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