Scottish Government

BARRIERS TO MODAL SHIFT

CHAPTER THREE Analysis of Travel Choices

Review of Existing Analysis of Travel Choices

3.1 The Glasgow area has many of the highest and lowest car ownership areas in Scotland, benefits from an extensive urban rail network, and has seen significant changes in patterns of bus services in recent years. In taking forward the developing transport strategy for the West of Scotland Strategic Transport Partnership it is important to understand the range of travel choices available throughout the area and the scope for mode shift to be achieved.

3.2 Four potential corridors were identified in the research brief as suitable for more detailed study:

• Milngavie/Bearsden to Glasgow
• Bishopbriggs to Glasgow
• East Kilbride to Glasgow
• Giffnock/Newton Mearns to Glasgow

3.3 These corridors all have rail, bus and car travel options available and include both high and low car ownership areas. To consider the characteristics of the corridors, eight sectors were identified. The boundaries for these were based on the zonal structure for the Strathclyde Integrated Transport Model. This is a four stage travel demand model which is developed and managed by SPT and can provide a detailed breakdown of modelled modal split across the area. These boundaries of the selected zones are shown in Figure 5.

Figure 5 Select Zones from SITM for Modal Split Analysis

3.4 Table 3 compares some key social and demographic indicators for the eight sectors in the four corridors.

Table 3 Comparison of Social and Demographic Characteristics

Source SITM courtesy of SPT

3.5 It can be seen that the highest car ownership is for Giffnock and Newton Mearns and the lowest is for the City North area. However, in broad terms the four outer areas show similar characteristics, and the four inner areas show similar characteristics. The city sectors generally have slightly more economically inactive people and elderly people than the outer sectors and there is a greater contrast between rich and poor for the two corridors on the north side of the city.

3.6 To consider the transport characteristics of the four corridors, the starting point was to identify what previous analysis had been undertaken by the relevant Councils, Strathclyde Passenger Transport (SPT) Executive and the Glasgow and Clyde Valley Structure Plan (GCVSP) Team.

3.7 Based on consultations with staff in each of these authorities, the recent previous analysis relevant to the current research and the main findings are summarised in Appendix A. A key issue to emerge from these local studies is the high importance given to public consultation. The organisations with a more regional brief, SPT and GCVSPT, have also undertaken detailed analysis of travel patterns and trends.

3.8 The local consultations demonstrate that if people see personal benefits from public transport improvements they are likely to support them. At present many car users have no intention of using buses, so do not support the changes to bus services which might make the services more attractive to them. Rail service improvements serve many fewer people than buses but are generally supported, including by car users, since car travellers also sometimes travel by rail.

3.9 Data was sought on mode split for each of the corridors. Unfortunately, survey data was only available for two of the corridors, as described in Appendix A. In the absence of recent survey data covering all corridors and all modes, SPT was able to supply estimated data on the car/public transport mode split from the Strathclyde Integrated Transport Model (SITM) trip matrices. The SITM travel matrix data had been estimated from origin-destination survey data collected over many years and some of the surveys dated back nearly 10 years. Nevertheless the estimation programmes used to develop the trip matrices involve sophisticated procedures that take account of the age of each data set so should have ensured that a reasonably robust representation was obtained. The reliability of the data is further demonstrated by the ability of SPT to calibrate the SITM travel demand against observed levels. Eight areas were chosen for analysis of mode split as follows:

• Bearsden/Milngavie;
• Bishopbriggs;
• East Kilbride;
• Giffnock/Newton Mearns;
• City North;
• City North West;
• City South;
• Cambuslang/Rutherglen.

3.10 Figure 6 shows the percentage of car travel for each of the four corridors for travel to work and Figure 7 shows the percentage of car travel for other trip purposes.

Figure 6 Mode Share for Car Commuting by Destination

3.11 For travel to the city centre, around 30% of trips are by car, but this varies considerably from area to area. Car attracts the highest mode share from Bishopbriggs, but the lowest mode share is from the city north area which is also on the Bishopbriggs to city centre corridor.

3.12 Of the four corridors being considered, Giffnock/Newton Mearns has the lowest mode share by car, but this is still considerably higher than other more central parts on the south side of the city such as Rutherglen.

3.13 Even though the mode share for trips from East Kilbride is similar when compared by type of destination, it has much the highest mode share by car overall since there are a lower proportion of trips to the city centre.

Figure 7 Mode share for Car Travel for Non Commuting Trips

3.14 For non commuting trips a different picture emerges (Figure 7). Bearsden/ Milngavie and East Kilbride have 85% of trips by car, and even for trips to the city centre, Bearsden/Milngavie has over 50% of trips by car.

3.15 East Kilbride and Bishopbriggs have higher percentages of car travel to non city centre destinations, but for all trips the car percentage is very similar for all four of the outer areas.

3.16 For trips to the city centre, the city north area has more trips by car than for other more central areas, contrasting significantly with the picture for commuting trips.

Mapping of Travel Choices

3.17 It is particularly important to understand the actual car and non car based travel choices available to people in the potential case study corridors. Generalised time and cost skims from the Strathclyde Integrated Transport Model have therefore been obtained from SPT for two scenarios:

• Modelled 2001 networks - Road and public transport skims and the associated planning data showing population employment etc.
• Forecast 2011 networks - Road and public transport skims with a best estimate of future transport schemes including the Larkhall railway, M77 completion, Glasgow Southern Orbital (GSO), M74 Completion, and Finnieston bridge. Since demand model test results for 2011 were not available with forecast Structure Plan planning data, the base planning data factored up in line with national economic trends was used.

3.18 This allows travel choices between modelled zones to be compared for car and public transport travel. Perhaps the clearest way to compare the car and non car choices available is to look at the ratio of car to non car accessibility by trip purpose.

3.19 Figure 8 shows the ratio of car to non car accessibility to work for 2001 am peak travel (i.e. car accessibility to jobs for each zone/non car accessibility to jobs for each zone)

3.20 It can be seen that of the four corridors East Kilbride is most dependent on car travel for access to jobs with large parts of the outer corridor having ratios of greater than 4. The other three corridors have similar overall ratios although Newton Mearns and Milngavie are further from the city centre and have higher ratios than Bearsden, Bishopbriggs and Giffnock.

3.21 A similar plot for the 2011 network is shown in Figure 8. This shows that over time the impact of the road building to the south of the city such as the M77, GSO, and M74 maintain the ratios at a similar level to the present day. However in the north of the city increasing levels of road congestion result in lower ratios with public transport becoming more competitive with car travel.

3.22 Figure 10 shows the ratio of car to non car accessibility for accessibility to people for 2001 am peak and Figure 11 shows the equivalent ratios for 2011. Access to population is the indicator most often used to describe accessibility levels independent of trip purpose.

3.23 The overall patterns of the accessibility ratios are similar to those for access to work, but since the population is more broadly distributed away from the city centre than employment, the overall level of the ratios tends to be higher indicating a higher dependence on car travel.

Figure 8 2001 Am Peak Accessibility to Jobs Ratio