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< Previous | Contents | Next > SCOTTISH TRANSPORT STATISTICS No 23: 2004 EditionChapter 12 PERSONAL AND CROSS-MODAL TRAVEL1. Introduction 1.1 This chapter includes information which was collected from individual people in surveys like the National Travel Survey and the Scottish Household Survey. Such surveys provide "person-based" "cross-modal" information, in contrast to most of the earlier chapters, which tend to be based on particular modes of transport. 1.2 The following new tables have been added for this edition:
1.3 The first six tables provide some statistics from the National Travel Survey. Because its Scottish sample is very small (see section 4.1), the results may be subject to large percentage sampling errors, due to the small number of cases upon which they are based (see section 3.6). Therefore, the NTS-based statistics should be regarded as broad indications (rather than precise measures) of the relative use of different modes of transport. 2. Main Points 2.1 The National Travel Survey’s estimated average number of trips per person per year was 997 in 2002, equivalent to an average of 2.7 trips per person per day. The estimated average number of trips per person per year has remained around the range 1,000 to 1,100 between 1985/86 and 2002, with fluctuations which could be due to sampling variability (see section 3.6). Since 1985/86, the estimated number of trips by car has risen by 54%, but there have been falls of 31% and 38% respectively in the estimated numbers of trips for which "walking" or "local bus" is the main mode. (Table 12.1) 2.2 Cars, vans and lorries accounted for over three-quarters (79%) of the average of around 6,500 miles which was travelled per year per person in 2002. Almost half the distance (49%: about 3,200 miles) was covered as the driver, and a further 31% (almost 2,000 miles) as a passenger. No other mode of transport accounted for more than 5%: "local bus" had the next highest share, with 5.0% of the total distance travelled (325 miles). Surface rail accounted for 4.7% (303 miles - the apparent fluctuations will reflect sampling variability, as discussed in Section 3.6), walking for only 3.0% (around 196 miles) and cycling for only 0.3% (21 miles). (Table 12.2) 2.3 The estimated average distance travelled per person per year has increased by 39% between 1985/86 (under 4,700 miles) and 2002 (almost 6,500 miles), with some fluctuations during the period, which may be attributed to sampling variability (see section 3.6). Almost all the increase was accounted for by travel in a car as a driver (up from around 1,900 miles to over 3,100 miles) or as a passenger (up from about 1,300 miles to just under 2,000 miles). (Table 12.2) 2.4 Over the period since 1985/86, the average length of a car trip has remained around 8-9 miles, compared to around 4-5 miles for local bus trips and very roughly 30 miles for train trips, with fluctuations that may be due to sampling variability. (Table 12.3) 2.5 In 2002, other personal business or other escort (20%) was the most frequent purpose of a trip, and three other purposes had large shares of the total: "shopping" (19%), "commuting" (16%), and "visiting friends at home" (12%). Again, there will be some fluctuations caused by sampling variability. (Table 12.4) 2.6 Of the trip purposes, "commuting" had the largest share of the total distance travelled in 2002 (20%: 1,322 miles). "Visiting friends at home", "other personal business", and "shopping" each accounted for 14-15% of the distance travelled (1,004, 990, and 919 miles respectively). "Holiday / day trip" accounted for 10% (about 653 miles) and "business" travel for 9% (589 miles). Some of the apparent changes between one period and the next will simply reflect sampling variability (Table 12.5) 2.7 Between 1985/86 and 2002, there were increases in the average length of trips for most purposes. For example, the average length of commuting trips rose from 5.4 miles to 8.2 miles, and the average length of shopping trips increased from 2.9 miles to 4.7 miles, with sampling variability likely to explain some period-to-period fluctuations. (Table 12.6) 2.8 The Scottish Household Survey (SHS) provides information about how often people aged 17 or over drive. In 2003, 52% of men, 35% of women and 42% of all people aged 17+ said that they drive "every day". A further 16% said they drove at least once a week (but not every day), 3% drove less frequently, 4% had a full driving licence but "never" drove, and 35% did not have a full driving licence. Changes in figures over the 5 years of the survey may be misleading, due to a change in the question in 2003 from being asked of the head of the household, or his or her spouse/partner, about all adult members of the household, to being asked of one randomly-selected adult member of the household about themselves. (Table 12.7) 2.9 The frequency of driving varied with age. In 2003, approaching three-fifths of people aged 30 to 49 were said to drive every day. As age rises the percentage falls to under 10% for people aged 80 and over. The frequency of driving also varied with the annual net income of the household of which the person was a member. Around two thirds of people aged 17+ living in households with an annual net income of £30,000 or more were said to drive every day, compared with only about a fifth of those living in households with an annual net income of up to £10,000. As far as location was concerned, 34% of people aged 17+ in large urban areas drove every day compared to around 56% of those in "accessible" rural areas. (Table 12.7) 2.10 The SHS asks adults (people aged 16 or over) on how many days, in the last seven days, they made a trip of more than a quarter of a mile by foot in order to go somewhere (e.g. to work, to the shops or to visit friends) - i.e. on how many days did they use walking as a means of transport (as distinct from walking solely for pleasure). In 2003, 53.5% of adults said that they had made a journey of more than a quarter of a mile by foot to go somewhere in the last seven days — a little more than in 1999 (51.7%). The apparent slight reduction from the figures for 2001 (54.5%) and 2002 (54.1%) could be due to sampling variability: each of these percentages has a "95% confidence interval" of +/- about 1% point. Young adults (aged 16-19) were the most likely to have walked to go somewhere, with 73% reporting this compared with only about 50% of those in their 50s and 60s. The percentage of adults who walked to go somewhere did not vary greatly with household income. (Table 12.8) 2.11 The SHS also asks adults how often, in the last seven days, they made a trip of more than a quarter of a mile by foot just for pleasure or to keep fit (jogging and walking a dog were counted under these purposes). In 2003, 43.5% of adults said that they had done so at least once - slightly more than in the previous four years of the survey. Men were slightly more likely than women to report that they had walked for pleasure or to keep fit (men: 47%; women: 41%). There was some variation with age: the percentage was highest for those aged 30-69 (47-48%) and lowest for those aged over 80 (20%). There was also some variation with household income: the percentage tended to rise with income, and was highest (53%) for adults living in households with an annual net income of over £30,000. (Table 12.8) 2.12 Information about the frequency of cycling is also collected by the SHS. In 2003, only 3% of adults said that, in the previous seven days, they had made a trip of more than a quarter of a mile by bicycle in order to go somewhere. The percentage was slightly higher for men and for younger adults. Only 4% said that, in the previous seven days, they had made a trip of more than a quarter of a mile by bicycle for pleasure or to keep fit. The percentage was slightly higher for men, and for those from the higher household income bands. Although the survey's results for previous years suggest a rise in the percentage of adults who report that they had cycled in 2003, to close to 1999 levels, this, and the apparent falls in earlier years, could simply reflect sampling variability. (Table 12.9) 2.13 Labour Force Survey results show that, between 1993 and 2003, there has been an increase in the percentage for whom a car or a van is the usual means of travel to work (from 65% in 1993 to 70% in 2003) and decreases in the percentages using buses (from 15% to 11%) and walking (from 15% to 12%). People who work at home are excluded from these figures. (Table 12.10) 2.14 There appears to have been little change in recent years in the average times taken to travel to work by the main modes of transport (in 2003: 20 minutes by car; 33 minutes by bus and 12 minutes by foot). The occasional fluctuations in the average times for ‘rail’ and ‘other’ may be due to sampling variability. (Table 12.11) 2.15 The longer-term trends are shown by statistics from the population censuses, which have collected information about travel to work since 1966. Excluding those that worked at home, the percentage of the working population using cars to travel to work has increased from 21% in 1966 to 68% in 2001 and the percentage using buses has fallen from 43% in 1966 to 12% in 2001. There has also been a significant fall in the proportion of the working population who walk to work, from 24% in 1966 to 12% in 2001. (Table 12.12) 2.16 SHS data can be used in more detailed analysis of travel to work patterns. The SHS shows that only 9.1% of employed adults worked from home in 2003, up on the 1999 figure. Over half of self-employed people worked from home. (Table 12.13) 2.17 Overall, the SHS found that the majority (69%) of adults who were employed and did not work at home used a car or van to travel to work in 2003. This percentage varied with sex (men: 72%, women: 65%), age (40-49 being highest, at 74%), type of employment (only 62% for those who work part-time), socio-economic classification (ranging from 58% for those in semi-routine occupations to 77% for those in lower managerial and professional occupations) and annual net household income (rising to 78% of those in the "£30,000+" band). The other usual means of travel to work were: walking (13%); bus (11%); rail (3%); bicycle (2%); and other modes (2%). Use of such modes of transport also varied. For example: in general, the greater the income of the household, the less likely a person was to walk or use the bus to travel to work; the percentage who walked to work was highest in "remote" small towns (24%) and the percentage who commuted by bus was highest in large urban areas (19%). The survey's results suggest that, between 1999 and 2003, there has been a slight decrease in the percentage walking to work or taking the bus, and a slight increase in the use of cars, consistent with the longer-term trends shown by Census figures. However, some of the apparent year-to-year changes could be due to sampling variability. For example, the percentage commuting by car/van has a "95% confidence interval" of +/- nearly 1.5% points, so the apparent rise from 66.5% in 1999 to 68.6% in 2003 could be the result of sampling variability. (Table 12.14) 2.18 The SHS also collects information about the usual main method of travel to school. In 2003, 53% of children in full-time education at school usually walked to school, 22% usually went by bus, 22% by car or van, 1% went by train, 1% cycled and about 2% used other means of transport (such as taxi or ferry). There was little difference between the sexes, but the usual means of travel varied greatly with age: 57% of pupils of "primary school" age (those aged up to 11) usually walked to school compared with only 47% of those of "secondary school" age (those aged 12 and over); 28% of "primary" pupils went by car or van compared with only 13% of "secondary" pupils; and only 12% of "primary" pupils usually travelled by bus compared with 36% of those of "secondary" age. The percentage who usually travelled by car or van tended to rise with household income, to 31% of pupils from households with an annual net income of £30,000 or more. The percentage who walked to school was lowest (26%) for those living in "remote" rural areas. The survey's results for the four years suggest slight falls in the percentages who walk to school and travel by bus, and a slight rise in the percentage who go by car. However, some of the apparent year-to-year changes may be due to sampling variability for example, the percentage walking to school has a "95% confidence interval" of about +/- 2% points, so the apparent fall from 54.7% in 1999 to 52.6% in 2003 could well be due to sampling variability. The NTS shows that the percentage of pupils aged from 5 to 16 who walk to/from school has decreased, and the percentage who go by car has risen, between 1985/86 and 1998/2000. (Table 12.15 & 12.16) 2.19 According to the International Passenger Survey (IPS), Scottish residents made an estimated 3.8 million visits abroad in 2002 with about 3.5 million visits (91%) being made by air. Glasgow was the main airport used and accounted for about 2.0 million visits (52% of all visits abroad), followed by Edinburgh (some 464,000 or 12%) and London Heathrow (355,000 or 9%). Around 293,000 visits abroad (8%) were made by sea, and roughly 39,000 (1%) were made using the Channel Tunnel. (Table 12.17) 2.20 Around four-fifths of Scottish residents' visits abroad were made for holiday purposes. Of these, 2.0 million (52%) were on a package holiday whilst 1.1 million (28%) travelled independently. There were 402,000 (10%) visits abroad to visit friends or relatives and 334,000 visits abroad for business purposes (9%). (Table 12.17) 2.21 Over 69% (2.7 million) of Scottish residents' visits abroad were made to EU countries and visits to other European areas totalled 466,000 (12%). Visits to Canada and the USA together totalled about 391,000 (10%). (Table 12.18) 2.22 The estimated number of visits abroad by Scottish residents increased from almost 2.3 million in 1993 to over 3.8 million in 2002, a rise of 69%. There were large percentage increases for each of the main purposes of visit, and for each of the main areas visited. One should not read too much into some of the apparent year-to-year changes, which may be due to sampling variability. (Table 12.19) 2.23 Some information on travel between different parts of Scotland is available from the Transport Model for Scotland (TMfS), which covers the area, broadly, from the Borders, through Perth and Dundee, stretching North East to Aberdeen and the surrounding area. The "base year" of TMfS is 2002. 2.24 It is estimated that, on an average weekday in 2002, over 5.2 million person-trips were made by car, bus or train across the boundaries of one or more of the "zones" which are within the area covered by the TMfS. (The basis of these estimates is explained in the "Notes and Definitions" and "Sources" sections below.) Almost half of these trips were within Glasgow and Strathclyde (excluding Ayrshire), a fifth were within Edinburgh and the Lothians, and 8% were within Aberdeen and the North East. Only 11% of trips were between different TMfS "sectors", with the largest such flows being roughly 45,000 person trips in each direction between Glasgow/Strathclyde and Ayrshire; around 40,000 person-trips each way between Edinburgh/Lothians and Glasgow/Strathclyde; about 30,000 person trips each way between Fife and Edinburgh/Lothians; and another 30,000 or so person-trips each way between Central and Glasgow/Strathclyde. The numbers travelling between the area covered by the TMfS and elsewhere in Scotland are estimated to be around 10,000 each way per weekday. (Table 12.20) 2.25 Of the 5.2 million "inter-zonal" person trips per weekday it is estimated that almost 4.3 million were by car. These accounted for over four-fifths of the total, and the main features of the pattern of trips by car were similar to (but smaller than) those described in the previous paragraph. There were also an estimated 0.9 million "inter-zonal" person-trips by bus or train per weekday. Slightly over half of these were within Glasgow/Strathclyde, and about 30% were within Edinburgh/Lothians. The only flow between different TMfS sectors which involved as many as 10,000 bus or train passengers each way per weekday was between Glasgow/Strathclyde and Ayrshire. (Table 12.20) 2.26 There was an average of almost 4.3 million trips per weekday by cars and goods vehicles. Over two-fifths were within Glasgow/Strathclyde, and a sixth were within Edinburgh/Lothians: in total, 87% were within TMfS sectors. The largest flows between areas were around 40,000 vehicles each way per weekday between Glasgow/Strathclyde and Edinburgh/Lothians, and about 35,000 vehicles each way per weekday between Glasgow/Strathclyde and Ayrshire. (Table 12.20) 2.27 The TMfS also produces estimates of the number of trips which are made by car, bus or train across the border with England. These suggest that, on an average weekday, around 10,000 people travel each way between Scotland and places in North East England, about 6,000 travel each way between Scotland and places in North West England, and some 7,000 people travel to and from other parts of England and Wales. (Table 12.21) 2.28 Over 118 million passenger journeys were made under concessionary fare schemes in 2002-03 10% more than in 2001-02. The figures for 2002-03 were influenced by the introduction of a national minimum standard of free off-peak local bus travel for elderly and disabled people in Scotland with effect from 30 September 2002. Because it was introduced midway through the financial year, its full effect will not be seen until the figures for 2003-04 are available. The most used mode was bus travel with just under 114 million passenger journeys (96%). Figures for the past ten years are only available for the Strathclyde Concessionary Travel Scheme. Over that period, the number of concessionary fare journeys decreased by 15% from around 73 million in 1992-93 to around 62 million in 2002-03. However, this reflects the overall fall in bus passenger journeys over the same period. (Table 12.22) 2.29 In 2003 Traveline Scotland received 464,700 telephone calls which was an increase of 31% over the previous year. Its Web site recorded 990,500 hits in 2003. (Table 12.23) 3. Notes and Definitions Travel by Scottish residents - statistics from the National Travel Survey (NTS) 3.1 The averages given in the tables are averages per head of population, and they will vary greatly from person to person: for example, there will be many people who do not travel on business at all, and others who travel thousands of miles on business. 3.2 A trip is defined as a one-way course of travel having a single main purpose. Outward and return halves of a return trip are treated as two separate trips. If a single course of travel involves a mid-way change of purpose then it is split into two trips (but trivial subsidiary purposes, such as a stop en route to buy a newspaper, are disregarded). 3.3 Main mode of transport: the mode that was used for the longest stage of the trip, where a trip involves more than one mode of transport (e.g. a bus and then a train). In the text, references to car trips include a few by van and lorry. 3.4 Length of a trip: the distance actually covered by the traveller, as reported by the traveller and not the distance "as the crow flies". 3.5 Other personal business: includes - e.g. - trips to the bank, doctor, hairdresser, library and church. 3.6 Sampling variability: Because the NTS's Scottish sample is small (see section 4.1), its results may be affected by large percentage sampling errors. Chapter 8 of the "NTS Technical Report 2000" provides information about the possible scale of the sampling errors for the survey's estimates for the three-year period 1998/2000. Tables on page 85 show the estimated "per person per year" averages, and their associated "95% confidence ranges", for different parts of Great Britain. The figures given for Scotland for 1998/2000 were:
Estimates based on smaller samples tend to be subject to larger sampling errors, all else being equal. Therefore, the 95% confidence ranges for the estimates are likely to be wider for 2002 than for the three years 1998/2000 taken together (because the sample was smaller in 2002 than in 1998/2000 taken together). And, the estimated numbers of trips made and distances travelled for some modes of transport could be subject to proportionately much greater sampling variability (because those modes were used by only a few people in the sample). Therefore, some of the apparent changes in some modes’ figures in Table 12.2 may be due to sampling variability: for example, the apparent fluctuations in the "surface rail" figures (285 miles in 1985/86, 468 miles in 1989/91, 154 miles in 1992/94, 256 miles in 1995/97, 479 miles in 1998/2000, 387 miles in 1999/2001 and 303 miles in 2002) are inconsistent with the changes in the overall figures for rail passenger numbers for the same period. It is likely that the fluctuations in the NTS results reflect the inclusion (by random chance) in the sample of more rail users, or greater rail users, in some years than in other years. Similarly, some of the NTS results in other tables may be affected noticeably by sampling variability. Frequency of driving, walking and cycling; and usual main methods of travel to school and travel to work - statistics from the Scottish Household Survey (SHS) 3.7 These notes do not cover the statistics on travel to work in Tables 12.10 to 12.12, which are from the Labour Force Survey and the Census of Population. 3.8 Annual net household income: this is the net income (i.e. after taxation and other deductions) which is brought into the household by the highest income householder and/or his/her spouse or partner, if there is one. It includes any contributions to the household finances made by other members of the household (eg "dig money"). In the case of households for which any of the main components of income were not known (for example, because of refusal to answer a question), the SHS contractors imputed the missing amounts, using information that was obtained from other households that appeared similar. 3.9 SHS urban / rural classification: the urban / rural classification shown in some tables was developed for use in analysing the results of the SHS. It is based on settlement sizes, and (for the less-populated areas) the estimated time that would be taken to drive to a settlement with a population of 10,000 or more. Each postcode in Scotland was classed as either "urban" or "non-urban", then clumps of adjacent "urban" postcodes, which together contained more than a certain total number of addresses, were grouped together to form "settlements". Six categories were then defined: Large urban areas - settlements with populations of 125,000 or more. These are around - but not the same as - Aberdeen, Dundee, Edinburgh and Glasgow. This category may (a) include areas outwith the boundaries of these four cities, in cases where a settlement extends into a neighbouring local authority, and (b) exclude some "non-urban" areas within the boundaries of these four cities. Other urban areas - other settlements of population 10,000 or more. "Accessible" small towns - settlements of between 3,000 and 9,999 people, which are within 30 minutes drive of a settlement of 10,000+ people. "Remote" small towns - settlements of between 3,000 and 9,999 people, which are not within 30 minutes drive of a settlement of 10,000+ people. "Accessible" rural areas - settlements of less than 3,000 people, which are within 30 minutes drive of a settlement of 10,000+ people. "Remote" rural areas - settlements of less than 3,000 people, which are not within 30 minutes drive of a settlement of 10,000+ people. 3.10 Full driving licence and frequency of driving: the SHS asks whether the person currently holds "a full driving licence (car or motorcycle)". For those who are said to hold a licence, the SHS asks how often the person drives nowadays. The interviewer records whichever of the categories shown in the table is the most appropriate, in the light of the answer. Prior to April 2003, these questions were asked of the head of the household, or his or her spouse/partner, about each adult member of the household. Since April 2003, these questions have been asked of a randomly-selected adult member of the household about themselves. Hence, results for previous years may not be entirely comparable with results for 2003. 3.11 Frequency of walking: the SHS asks on how many of the last seven days the person made a trip of more than quarter of a mile by foot. The interviewer asks about walking for the purpose of going somewhere, such as work, shopping or to visit friends. The interviewer then asks about walking just for the pleasure of walking or to keep fit or to walk the dog. 3.12 Frequency of cycling: the SHS asks on how many of the last seven days the person made a trip of more than quarter of a mile by bicycle. The interviewer asks about cycling for the purpose of going somewhere, such as work, shopping or to visit friends. The interviewer then asks about cycling just for the pleasure or to keep fit. 3.13 Socio-economic classification: the social class categories used in the SHS match those used in all official statistics and surveys. The National Statistics Socio-economic Classification (NS-SEC) has been designed to group together, as far as possible, people with similar levels of occupational skills. The version of the classification used for this analysis has eight categories, although the final one is not used in the "travel to work" table, as it refers only to those who have never worked or are long-term unemployed. The seven classes used are:
Scottish residents' visits abroad - statistics from the International Passenger Survey 3.14 The International Passenger Survey is designed to be representative of all people travelling in and out of the UK in terms of: the usage of air, sea and tunnel; UK residents going abroad and foreign residents coming to the UK; different types of traveller (eg holiday, business, etc); and travel to and from different parts of the world. However it is not designed to produce results which are representative for different regions of residence within the UK. While the survey's procedures should not lead to any major bias in the estimates for Scottish residents, the "luck of the draw" inherent in the sampling process may result in their being over-represented in the survey in some years, and under-represented in other years. 3.15 Visits abroad: The figures include all tourists who make trips which last no more than a year, those travelling to Eire have been included in the IPS since 1999. 3.16 Miscellaneous and other purposes: includes visits for study, to attend sporting events, for shopping, health, religious or other purposes, and multi-purpose visits for which no one purpose predominates. 3.17 Area visited: in cases where two or more countries are visited, a person is counted on the basis of the one country in which he or she stayed for the longest time. "Inter-zonal" trips made on an average weekday - estimates from the Transport Model for Scotland (TMfS) 3.18 These are the estimated annual average numbers of trips made per weekday between or within the areas shown, using the specified modes of transport (for example, they do not include trips made by foot, by bicycle, or by motorcycle). The figures represent the estimated total flows over the whole 24 hours of an average weekday. A return journey, from A to B and back again, on the same day, would be counted as two trips: one from A to B and one from B to A. 3.19 The figures are estimates of the numbers of "inter-zonal" trips - i.e. trips which cross the boundary of at least one of the zones used in the Transport Model for Scotland (TMfS). The zones used in the model are constructed by amalgamating Population Census output areas. The model's zones vary in size from area to area, depending on factors such as the size and density of the population and the nature of the transport network that the model must represent. As a result, there is no simple definition of a zone. Some Council areas have many zones (e.g. there are 180 in Edinburgh, and 239 in Glasgow); others have only a few (e.g. there are 10 in East Lothian and 11 Midlothian and 21 in West Lothian). It follows that a trip of a particular length will be more likely to be counted as an "inter-zonal" trip if it is in (say) Edinburgh than if it is in (say) East Lothian. 3.20 'Person trips' relate to the number of people travelling by the specified modes of transport, and 'vehicle trips' to the numbers of vehicles going between the specified areas. Thus, for example, if a car containing two people goes from A to B, it is counted as two person trips and one vehicle trip. 3.21 The areas identified in the table are "sectors" within the TMfS. These correspond broadly (but not necessarily exactly) to the areas of the similarly-named former Regions and/or current Councils. Some of these sectors do not contain many TMfS zones - for example, the "Borders" sector contains 11 zones, and the "Perth & Kinross" sector contains 23 zones. All else being equal, the larger the zones are within a sector, the smaller the proportion of the trips within the sector that will be treated as "inter-zonal" trips - and, hence, the smaller the proportion that will be represented within the model. 3.22 "Elsewhere in Scotland" refers to those parts of Scotland which are outwith the TMfS model area: broadly, Arran, Argyll & Bute, Highland, Moray, Orkney, Shetland and the Western Isles. The model does not hold information regarding trips which are wholly outwith its model area, such as a trip between Inverness and Dingwall, which would be wholly within the "elsewhere in Scotland" area. 3.23 The estimated average number of trips originating in an area usually differs from the estimated number with a destination in that area - for example, compare the estimates of 1,132,000 person trips with a destination in Edinburgh & Lothians and 1,140,000 trips originating in Edinburgh & Lothians. This is because the estimation process (which is described in section 4) is mainly based upon survey data covering the 7 a.m. to 7 p.m. period, and cannot take full account of trips which involve returning later in the evening. Therefore, the TMfS-based estimates indicate broadly the levels of flows within Scotland, but do not provide precise measures. 3.24 The model's estimates of the number of cross-border trips by bus and train may not be particularly reliable, because of the way that they are produced - see section 4. 4. Sources 4.1 Travel (within GB) by Scottish residents (Tables 12.1 to 12.6) 4.1.1 Information about travel (within Great Britain) by Scottish residents is obtained from the National Travel Survey (NTS). This collects "travel diary" details from a sample of households across Great Britain. Travel for all private purposes is included. Trips in the course of work are included if they fulfil the requirement that the main reason for the journey is for the traveller to reach the destination. However, travel in the course of work to convey passengers or to deliver goods is excluded, such as travel in the course of their work by bus drivers, lorry drivers and postmen. Trips off the public highway, such as country walks, are excluded. 4.1.2 Prior to 2002, the NTS was not designed to provide reliable estimates for Scotland for single years: the sample included only a few hundred Scottish households each year. Therefore, the samples for a number of years had to be combined in order to produce Scottish results, and even they could be subject to considerable sampling variability. In 2002, the NTS’s sample size was increased greatly, enabling the production of results for individual calendar years with effect from 2002. However, the sample size was less in 2002 than in the previous three years taken together, and therefore the results for 2002 could be subject to greater sampling variability than those for 1999/2001 taken together. Section 3.6 provides some information about sampling variability. 4.2 Frequencies of driving, walking and cycling; and usual main method of travel to school (Tables 12.7 to 12.9 and 12.16) 4.2.1 Information on these and some other transport-related topics is collected by the Scottish Household Survey, which started in February 1999. The SHS collects information on a wide range of topics, to allow exploration of the relationships between different sets of variables. Interviewing takes place throughout the year. 4.2.2 The SHS is a survey of private households. For the purposes of the survey, a household is defined as one person or a group of people living in accommodation as their only or main residence and either sharing at least one meal a day or sharing the living accommodation. A student's term-time address is taken as his/her "main residence", in order that he/she is counted where he/she lives for most of the year. The sample was drawn from the Small User file of the Postcode Address File (PAF) which does not include (eg) many nurses homes, student halls of residence, hostels for the homeless, other communal establishments, mobile homes, and sites for travelling people. Therefore, the SHS cannot produce figures completely representative of people living in Scotland: its target population includes only a proportion of the student population, for example. People living in bed and breakfast accommodation may be included, if it is listed in the Small User file of the PAF and if it is their sole or main residence. Prisons, hospitals and military bases are excluded. 4.2.3 Each year, SHS interviews are conducted with a randomly-chosen sample of (on average) over 15,000 households across Scotland. Within each Council area, the sample is stratified using a geo-demographic indicator in order that it will be representative across that Council's area. A higher sampling fraction is used in the areas of the Councils with the smallest populations, in order that (in each two-year period) there is a minimum of 550 household interviews per Council. The results are then reweighted so that they will be representative of Scotland as a whole. 4.2.4 The SHS interview is conducted in two parts. The first part is with the highest income householder, or his/her spouse/partner (if any), who answers questions about the household and its members. This part of the interview provides the information about the ages and sexes of household members, and about the annual net household income. Prior to April 2003, it included questions about the type of driving licence (if any) held by each adult member of the household, and about the frequency of driving of those who hold a full driving licence. It also provides the information about the usual main method of travel to school for one randomly-chosen schoolchild member of the household (if there is one). Because the information is collected for at most one schoolchild per household, in the analysis proportionately greater weight is given to cases where there are greater numbers of schoolchildren in the household. 4.2.5 The second part of the SHS aims to obtain results which are representative of Scottish adults by interviewing a randomly-chosen adult (aged 16+) member of the household (who may happen to be the person who answered the questions in the first part of the interview - for example, this is always the case for single pensioner households). The second part of the survey has fewer respondents because some of the randomly-chosen adults cannot be interviewed, perhaps because they choose not to take part in the survey or perhaps because the interviewer cannot contact them. This part of the interview provides the information about the type of driving licence (if any) held by the randomly selected adult (since April 2003), about the frequency of driving of those who hold a full driving licence (since April 2003), about the frequency of walking and the frequency of cycling and, in cases where the person is employed, about the place of work and the usual means of travel to work. Questions are also asked about journeys made on the previous day (the "Travel Diary"). These include the start and end times of each stage of the journey, the mode of transport used, the purpose of the journey, and experiences of congestion. Because at most one adult is interviewed per household, in the analysis proportionately greater weight is given to cases where there are greater numbers of adults in the household. For the "Travel Diary" questions, further weighting is given according to the day of the week and the economic status of the adult. 4.2.6 Although the SHS's sample is chosen at random, the people who take part in the survey will not necessarily be a representative cross-section of the people of Scotland. For example, purely by chance, the sample could include disproportionate numbers of certain types of people, in which case the survey's results would be affected. In general, the smaller the sample from which an estimate is produced, the greater the likelihood that the estimate could be misleading. As an example, Table 12.14 shows that the percentages of people aged 16-19 who usually travelled to work in various ways were calculated from data for only 104 commuters of that age in the SHS in 2003. It was estimated that 1% of them cycled to work - but if, purely by chance, the sample had contained just two more 16-19 year olds who cycled to work, the estimate would have been 3% rather than 1%. Results produced from a small sample could therefore be greatly affected by sampling variability. The larger the sample, the less likely it is that the results will be affected greatly by sampling variability. The Transport Statistics publications of SHS results and the SHS Annual Reports (see sections 5.3 and 5.4) provide examples of the "95% confidence limits" for estimates of a range of percentages calculated from sub-samples of a range of sizes. 4.2.7 The above information relates only to sampling variability. The survey's results could also be affected by non-contact / non-response bias: the characteristics of the (roughly) one-third of households who should have been in the survey but who could not be contacted, or who refused to take part, could differ markedly from those of the people who were interviewed. If that is the case, the SHS's results will not be representative of the whole population. Without knowing the true values (for the population as a whole) of some quantities, one cannot be sure about the extent of any such biases in the SHS. However, comparison of SHS results with information from other sources suggests that they are broadly representative of the overall Scottish population, and therefore that any non-contact or non-response biases are not large overall. Of course, such biases could be more significant for certain sub-groups of the population. In addition, because it is a survey of private households, the SHS does not cover some sections of the population - for example, it does not collect information about many students in halls of residence. The SHS technical reports (see section 5.4) provides more information on these matters. 4.3 Travel to work (Tables 12.10 to 12.14) 4.3.1 The information about the usual means of travel to work and the time taken to travel to the usual place of work shown in tables 12.10 and 12.11 is obtained from the Labour Force Survey using questions which have been included in those survey interviews which have been conducted in the Autumn each year since 1992. The tables include the self-employed, those on Government training schemes and unpaid family workers as well as employees, but exclude those working at home, and those whose workplace or mode of transport to work was not known. The LFS is a household survey covering 60,000 households each quarter in GB, and about 6,000 households per quarter in Scotland. 4.3.2 Table 12.12 provides some Census of Population information about travel to work. There have been some changes in the categories used — for example, the 1966 Census had a category described as "none" which was included in the 1971 Census under its "On foot and none" category; the 1971 Census had a category described as "Public Transport" which was separate from the categories for "Train" and "Bus"; and the 1966 and 1971 Census "travel to work" figures did not identify separately those who were working at home, so they are included in the figures for those years. However, the effect of such differences on the statistics will be small compared to the scale of the changes in the shares of the main modes of travel. 4.3.3 Information about travel to work is also collected by the SHS (see section 4.2 above), which is the source for tables 12.13 and 12.14. 4.4 Scottish residents' visits abroad (Tables 12.17 to 12.19) 4.4.1 This information is collected by the International Passenger Survey (IPS), from a sample of passengers returning to the UK by the principal air, sea and tunnel routes (excluding some routes which are too small in volume or which are too expensive to be covered). Travellers passing through passport control during the day are randomly selected for interview (interviewing is suspended at night). A weighting procedure takes account of the non-sampled routes and time periods. For example, the figures for certain airports are "uplifted" to take account of the passenger numbers at the other UK airports which are not covered by the survey. Edinburgh and Glasgow are the only Scottish airports at which interviewing takes place, so it is not possible to produce estimates for other Scottish airports but the figures for both Edinburgh and Glasgow are uplifted to take account of the non sampled airports. 4.4.2 The figures in the tables are based on interviews with Scottish residents who returned to the UK. This is the Office for National Statistics' standard practice for producing such estimates, as it can then also analyse other information that is collected in the interviews (such as the amount that people say that they spent while on holiday). 4.4.3 The survey covers both adults and children, and is voluntary - for example, the response rate was 81% in 1998, and the results reported in these tables for that year are based upon interviews with about 2,300 Scottish residents. 4.4.4 The IPS data used in the tables are adjusted to take account of the fact that not all people respond to questions regarding area of residence. This means that tables produced by area of residence will not always exactly match other published data regarding trips abroad by UK residents. 4.5 Trips made on an average weekday (Table 12.20 and 12.21) 4.5.1 These figures were provided using the Transport Model for Scotland (TMfS). This covers the areas from the Borders, through Perth and Dundee, stretching North East to Aberdeen and the surrounding area, in which lives roughly 95% of the population of Scotland. 4.5.2 The area covered by the model is divided into 1,133 zones. The model uses planning data for each zone (e.g. population, number of households, car ownership, employment, number of employed residents) to calculate the number of trips that would be expected to be generated. It also uses information collected by traffic counts, roadside interviews and surveys of passengers on public transport. Some of the information was collected specifically for the model (the programme of surveys to collect data for TMfS started in 2002, which is its base year). TMfS also uses information from other sources, such as ‘donor’ models (such as the Strathclyde Integrated Transport Model), the 2001 Census of Population and the Scottish Household Survey (which has been conducted continuously since February 1999). Data collected in other years were "factored" to represent the base year. The quality and coverage of the data that are held within the TMfS vary between different areas and different parts of the transport network. This is the result of the historical interest in the movement of people and goods between various points on the transport network, and the resultant availability of data. However, the base information used for the TMfS is more robust and comprehensive than that used for the former Central Scotland Transport Model. 4.5.3 The pattern of travel movements is held in a series of trip matrices covering the morning peak period, the evening peak period and the intervening off-peak period. Taken together, these matrices can be combined to provide a matrix reflecting trip movements during the period 7 a.m. to 7 p.m. on a typical weekday. Daily, monthly and annual averages can then be derived by grossing-up these figures using time series data sources. The resulting expected flows around the transport network are then "calibrated" and "validated" for each modelled time period using information about the actual numbers of trips that were made on particular routes. 4.5.4 Applying the calibration and validation process to the "expected numbers of generated trips" calculated by the model produces estimates of the numbers of trips which are consistent with the observed traffic counts and the results of surveys and interviews. The estimated numbers of trips for the areas shown in the table were then produced by aggregating the estimated numbers of trips for the relevant zones. 4.5.5 The model's estimates of the numbers of people travelling by bus and train across the border with England are less reliable because it uses its standard set of "public transport" factors to "gross up" the cross-border passenger numbers obtained (e.g.) from surveys and passenger counts which were carried out at certain times on certain days. Because local bus services account for the vast majority of public transport in Scotland, the model's standard public transport "grossing-up" factors mainly reflect the pattern of local bus passenger usage - so applying these factors to the data for cross-border bus and train traffic may not take proper account of the different patterns of such traffic. 4.6 Passenger journeys made under concessionary fare schemes (Table 12.22) 4.6.1 The figures for the Strathclyde Concessionary Travel scheme were supplied by Strathclyde Passenger Transport (SPT); the figures for the other schemes were collected from local authorities using the Local Financial Returns form LFR5. 4.6.2 Local authorities were asked to provide numbers of passenger journeys on the same basis as the expenditure on concessionary fares that they report in the LFR5. This relates to concessionary fares for elderly people, for people with visual or other disabilities, and for children (but excluding any element of school transport costs). In cases where authorities participate in a joint scheme (other than the Strathclyde one) for some modes of transport, they were asked to provide the estimated numbers of journeys for those modes which correspond to their shares of the joint scheme's total numbers of journeys for those modes. It is appreciated that such estimates may not be precise. 4.6.3 SPT was able to provide passenger numbers from its records for the Strathclyde Concessionary Travel scheme for several years; figures for the passenger numbers for other schemes are only available for 2000-01 onwards because that was the first year for which that information was requested from local authorities using the LFR forms. 5. Further Information 5.1 The Scottish Executive statistical bulletin "Travel by Scottish residents: some National Travel Survey results for 1998/2000 and earlier years" provides a range of National Travel Survey statistics for Scotland, and some information about the survey. More details of this publication are given under "Scottish Executive Transport Statistics publications". The National Travel Survey is also described in the Department for Transport publications "Focus on Personal Travel" and "National Travel Survey" bulletins, and in the "National Travel Survey Technical Report". 5.2 Enquiries regarding National Travel Survey statistics, and transport statistics from the Labour Force Survey, should be directed to Spencer Broadley of the Department for Transport (tel: 020 7944 3097) 5.3 There are a number of publications on the Scottish Household Survey. The main transport-related results are given in three series of bulletins:
More details of these publications appear under "Scottish Executive Transport Statistics Publications". 5.4 There are also a number of SHS publications. The main one is "Scotland's People", a detailed Annual Report, which provides many tables of results on a wide range of the topics covered by the survey. There are also "technical" reports which contain information about the survey's procedures (such as the sample design and the method of reweighting) and an edited version of the questionnaire. In addition, between 1999 and 2002, a series of SHS bulletins, provided a selection of SHS results, including some on transport-related topics, together with a brief description of the survey. All the SHS publications are available from the Stationery Office bookshop. 5.5 Enquiries regarding the Scottish Household Survey should be directed to the SHS Project Manager: Josephine Dean of the Scottish Executive Central Research Unit (tel: 0131 244 8420). 5.6 The annual report on the International Passenger Survey is called "Travel Trends", and is published by the Stationery Office. Enquiries regarding the International Passenger Survey should be directed to Josh Lovegrove of the Office for National Statistics (tel: 020 7533 5765). 5.7 Further information or guidance on the detailed application of the Transport Model for Scotland can be obtained from Diarmid Lindsay, the Scottish Executive Transport Division 1 (tel: 0131 244 7260) or Kevin Lumsden, MVA (tel: 0131 220 6966). 5.8 Further information about the numbers of passenger journeys made under concessionary fare schemes can be obtained from John Valentine of the Scottish Executive Local Government Finance Statistics branch (tel: 0131 244 7033) and, in the case of the Strathclyde Concessionary Travel Scheme, from Anne Gibson, Strathclyde Passenger Transport (tel: 0141 333 3253). 5.9 Further information about the number of telephone calls and Web site hits for Traveline Scotland can be obtained from Ron Cruickshank, the Scottish Executive Transport Division 3, (0131 244 0153). Figure 12.1 Calls to Traveline Scotland in 2002 |
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