User guide – Personal and crossmodal travel

Notes and definitions

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 (e.g. 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.

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 size, 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 fewer than 3,000 people, which are within 30 minutes' drive of a settlement of 10,000+ people.
Remote rural areas - settlements of fewer than 3,000 people, which are not within 30 minutes' drive of a settlement of 10,000+ people.

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 onwards.

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.

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.

Sampling variability

As with the NTS, the SHS is a sample survey so results will be subject to sampling variability. More information including a look up table to calculate confidence intervals can be found in the background section of the Transport and Travel in Scotland or SHS: Travel Diary publications.

International Passenger Survey

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 (e.g. 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 sample-based nature of the survey may result in their being over-represented in the survey in some years, and under-represented in other years.

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.

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.

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 - the Transport Model for Scotland (TMfS)

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.

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, 11 in 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.

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.

The areas identified in the table are sectors within TMfS. These correspond broadly (but not necessarily exactly) to the Strategic Development Planning areas 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.

Elsewhere in Scotland refers to those parts of Scotland not identified in other sectors: broadly, Argyll & Bute, Eilean Siar, Highland, Moray, Orkney Islands, and Shetland Islands.

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 111,000 person trips with a destination in Dumfries & Galloway and 112,000 trips originating in Dumfries and Galloway. This is because the estimation process (which is described in section 11.8) 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.

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.

Sources

Scottish Household Survey - Frequencies of driving, walking and cycling; and usual main methods of travel to school and travel to work (Tables 11.10 to 11.13 and 11.17 to 11.19 and 11.21 to 11.23)

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.

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 many nurses' homes, student halls of residence, hostels for the homeless, other communal establishments, mobile homes, and sites for travelling people.

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.

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 provides household members' age and gender , and 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 the frequency of driving. Main method of travel to school was also collected (for one randomly-chosen schoolchild member of the household). As the information is collected for one schoolchild per household, proportionately greater weight is given to cases with greater numbers of schoolchildren in the household.

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). This part has fewer respondents as not all randomly-chosen adults are available. Information on the frequency of walking, place of work , usual method of travel to work etc are collected 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. As one adult is interviewed per household, proportionately greater weight is given to cases with 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.

Although the SHS's sample is chosen at random, respondents will not necessarily be a representative cross-section of the people of Scotland. E.g. 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. SHS publications (see sections 11.10 and 11.11) provide examples of the 95% confidence limits for estimates of a range of percentages calculated from sub-samples of a range of sizes.

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 provide more information on these matters.

Travel to work (Tables 11.14 to 11.16)

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 11.14 and 11.15 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.

Scotland's Census took place on Sunday 27 March 2011 with the chief purpose of providing an accurate population count as well as collecting data on key characteristics of individuals in Scotland, including their travel to work. Some individuals are missed in the Census, and this under-counting does not usually occur uniformly across all geographical areas or across other sub-groups (for example, by age and sex) of the population.

To fill the gap, the National Records for Scotland (NRS) implemented a coverage assessment process to estimate the population that was missed, also identifying and adjusting for the people who were counted more than once or who were counted in the wrong place. Carrying out this work allowed a census estimate of the entire population to be obtained.

The methods were largely based on those developed by the Office for National Statistics (ONS). The ONS systems were also implemented although adapted as necessary to cope with Scotland specific data. ONS have produced a full suite of methodology papers detailing the statistical theory and practical application of the methodology. They can be found here: http://www.ons.gov.uk/ons/guide-method/census/2011/census-data/2011-census-user-guide/quality-and-methods/methods/coverage-assessment-and-adjustment-methods/index.html

It was not always practical or appropriate to replicate exactly what was done for the rest of the UK due to differences in fieldwork processes, data capture and processing and also the availability of comparator data sources. The ONS documentation should be read bearing in mind there were small differences between Scotland and the rest of the UK.

Table 11.16 provides some Census of Population information about travel to work. Information about travel to work has been collected in population censuses since 1966. 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 .

Information about travel to work is also collected by the SHS,which is the source for tables 11.17 and 11.18.

Hands Up Scotland Survey (Table 11.23a)

Established in 2008, the Hands Up Scotland Survey is the largest national dataset to look at travel to school across Scotland. The project is funded by Transport Scotland and is a joint survey between Sustrans and Scottish local authorities.

Schools across Scotland complete the survey by asking their pupils 'How do you normally travel to school?' The responses are then sent to local authority officers who collate the data and return it to Sustrans' Research and Monitoring Unit for overall collation, analysis and reporting.

A Parliamentary Order was passed designating Sustrans as Official Statistics Providers in the production of Hands Up Scotland on 1st June 2012. Sustrans is currently looking to acquire National Statistics status for the survey.

International Passenger Survey - Scottish residents' visits abroad (Tables 11.24 to 11.26)

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. Prior to 2005, Edinburgh and Glasgow were the only Scottish airports at which interviewing took place. Prestwick airport was added to the survey in 2005 and Aberdeen has been collected since 2009. These are uplifted to take account of the non sampled airports. Rosyth was included in quarters 2, 3 and 4 of 2007 and quarters 2 & 3 of 2008.

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).

The survey covers both adults and children, and is voluntary - for example, the response rate was 80% in 2003, and the results reported in these tables for that year are based upon interviews with about 2,000 Scottish residents.

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.

Transport Model for Scotland - Trips made on an average weekday (Table 11.27)

These figures were provided using the Transport Model for Scotland 2012. This model covers the Scottish Strategic Mainland Transport Network, and also includes representation of travel patterns between Scotland and England.

The area covered by the model is divided into 720 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. The information collected and used to develop the model started in 2002 and continued through to 2012, which is the 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 to develop TMfS12 is more robust and comprehensive than that used in former versions of the national model.

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.

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.

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.

Passenger journeys made under concessionary fare schemes (Table 11.29)

The figures for the Strathclyde Concessionary Travel scheme were supplied by Strathclyde Partnership for Transport (SPT); the figures for other schemes were collected from Transport Scotland (national schemes) and from local authorities using the Local Financial Returns form LFR5.

The National Concessionary Travel bus scheme was introduced on 1st April 2006, which allows elderly and disabled free travel on all scheduled bus services in Scotland. This is administered by Transport Scotland and replaced any local bus schemes. The Young People's Concessionary bus Travel Scheme started in 8 January 2007, aimed at 16 to 18 year olds (inclusive) and full time volunteers (aged under 26).

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 exclude school transport).

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.

Further information

Within Scottish Transport Statistics:

Chapter 1 – Road vehicles,
Chapter 5 – Road Traffic (including congestion)
Chapter 12 – International comparisons

Other Transport Scotland Publications:

Transport and Travel in Scotland – includes more detailed analysis of SHS data, in particular:

Table 11 – car sharing
Table 16 and 17 – Reasons for choice of travel to school mode
Table 18a – bicycle access
Table 21 – Park and ride
Table 28 – Frequency of bus and train use
Tables 31 and 32 – Concessionary pass use

Scottish Household Survey Travel Diary, published as part of Transport and Travel in Scotland – includes detailed tables using the Travel Diary dataset, in particular:

Table 2 – journeys by mode of transport

Table 2a&b – journey and stage distance by mode of transport
Table 3 – Purpose of travel
Table 4a & 5a – mode of transport by journey distance

SHS Local Authority Results, published as part of Transport and Travel in Scotland – provide breakdowns of SHS data by Local Authority, Regional Transport Partnership and Urban Rural Classification. In particular:

Table 2 – journeys by mode of transport
Table 2a&b – journey and stage distance by mode of transport
Table 3 – Purpose of travel
Table 4a & 5a – mode of transport by journey distance

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