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Background Notes

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Purpose of Survey

The National Travel Survey (NTS) is a household survey on the travel behaviour of respondents. It was conducted as a module of the Quarterly National Household Survey (QNHS) in the fourth quarter (October – December) of 2016. A similar module was included in the QNHS in the fourth quarter of 2012, 2013 and 2014 respectively. The NTS will be used to compile statistical indicators for journey purpose and modes of travel, which will help monitor the implementation of existing transport policy and will inform future transport initiatives.

The QNHS is a comprehensive nationwide survey of households. The primary purpose of the survey is to produce quarterly labour force estimates in compliance with the requirements of Council Regulation (EC) No. 577/98. It also covers topics of specific social interest in additional modules each quarter. Further details on the QNHS are available on the CSO website at the following link

Reference Period

The National Travel Survey for the reference year 2016 was included as a module to the QNHS in the three months from October to December 2016 (Quarter 4). The travel reference days, i.e. the days for which travel data was collected, covered the period October 10th 2016 – January 8th 2017.


The NTS questionnaire was designed by the Central Statistics Office in consultation with the Department of Transport, Tourism and Sport (DTTaS) and the National Transport Authority (NTA). The questionnaire was included on waves two to five of the QNHS sample and was answered by all persons aged 18 years and over in this sample. The section on 'Sample Design' below details how the sample was selected.

A copy of the NTS 2016 questionnaire is available on the CSO website at QNHS National Travel Survey Q4 2016 (PDF 649KB) (PDF 650KB).

Individual Reference Person

This survey was asked of persons aged 18 years and over on waves two to five of the QNHS sample. Only direct respondents were included in the NTS survey (i.e. no third party responses were permitted).

Data Collection

Information was collected on tablet computers, using computer-assisted personal interviewing (CAPI) software.

Sample Design

A two-stage sample design is used. A new sample was introduced in Quarter 4 2012 following the 2011 Census of Population and an additional new sample also based on the 2011 Census of Population will be introduced incrementally from Quarter 3 2016. The sample frame of households is clustered into blocks (small areas) with each block containing a minimum of 60 occupied households on the night of the 2011 Census of Population. In the case of the sample introduced in 2012, the sample frame is stratified using administrative county and population density while the sample introduced in 2016 is stratified using administrative county and the Pobal HP (Haase and Pratschke) Deprivation Index. In the first stage 1,300 blocks are selected using Probability Proportional to Size (PPS) sampling and in the second stage, 20 households are selected using Simple Random Sampling (SRS). This ensures that each household in the sample frame has an equal probability of selection and results in a total quarterly sample of 26,000 households. The actual achieved sample varies over time depending on the level of response.

Households are asked to take part in the survey for five consecutive quarters and are then replaced by other households in the same block. Thus, one fifth of the households in the survey are replaced each quarter and the QNHS sample involves an overlap of 80% between consecutive quarters and 20% between the same quarter in consecutive years. As the new sample based on the 2011 Census of Population was introduced incrementally across each quarter from Quarter 4 2012 to Quarter 4 2013, the new sample is fully effective from Quarter 4 2013.

Householders are not asked to participate in the module in their first quarter participating in the survey. This is primarily to minimise response burden on the householders.

The survey results are weighted to agree with population estimates broken down by age, sex and region and are also calibrated to nationality control totals. The population estimates for April of each year are published in a separate release.

Grossing Effect

The QNHS grossing procedure aligns the distribution of persons covered in the sample with independently determined population estimates at the level of sex, five-year age group and region.

The grossing factors applied in the processing of the NTS were calculated in the same manner but differ from those that were used in the preparation of the main QNHS estimates as the NTS was asked of a sub-sample of the overall QNHS sample (persons aged 18 years and over and waves two to five of the QNHS sample).

Statistical Significance

All estimates based on sample surveys are subject to error, some of which is measurable. Where an estimate is statistically significantly different from another estimate, it means that we can be 95% confident that differences between those two estimates are not due to sampling error.

Note on Tables

The sum of row or column percentages in the tables in this report may not add to 100.0% due to rounding.

Guide to Using NTS Results

Care should be taken when interpreting the results or when comparing them with other data sources such as POWSCAR. POWSCAR is the 2011 Census of Population Travel to Work, School and College Census of Anonymised Records and is available at the following link POWSCAR should be used as the definitive source of data on travel to work, school and college. When comparing the NTS results to POWSCAR data, it should be noted that the NTS journey purpose of ‘work’ includes both commuter and business travel while the POWSCAR data includes commuter travel only. The NTS collected travel data for a specific day while the Census collected travel data for the ‘usual’ journey to work, school or college. Similarly, when examining issues such as the mode share for travel to school/education, it is important to note that the NTS doesn't accurately reflect the mode share for the whole student population as the NTS only sampled persons aged 18 years and over.

Data from other international sources/surveys indicates that there can be significant seasonal variations in travel patterns. The NTS travel reference days spanned the Christmas and New Year holiday period when travel patterns may be atypical. This period also encompasses the shortest days and some of the coldest and wettest weather of the year. Estimation of survey results from data relating to only one day’s activity for a sample of journey introduces a statistical variability which would not be present if a full year’s data had been collected.

Key Definitions and Descriptions


This survey was asked of adults, aged 18 years and over, resident in the Republic of Ireland.


A journey is defined as a one-way course of travel from location A to location B for the purpose of carrying out a specific activity at location B. A location could be a single premise (e.g. a house, an apartment, a shop, an office, etc.) or a complex of premises (e.g. a shopping centre, a factory site, a hospital, etc.). Return trips were recorded as separate journeys. To be relevant to the survey, journeys must have:

  • Commenced in the travel reference day (it may end the following day)
  • Been at least 100 metres in length (approximately a one minute walk)
  • Comprised exclusively of domestic travel (all stages of foreign travel were excluded)
  • Not formed an integral part of a respondent's routine employment (e.g. milkman, taxi driver, etc.)

Journey Purpose

The purpose of a journey is governed by what action was taken at the end of the journey.

Mode of Travel

Where a journey consists of more than one mode of travel, the main mode of travel is determined by the mode of travel used for the greatest distance. In the event of there being more than one main mode of travel (i.e. when two or more modes are of equal distance), then the main mode of travel is determined by the mode of travel used for the earliest stage of the journey.

Journey Duration

This is calculated as the sum of time spent on each stage of the journey and not the difference between the start and end time of a journey.

Travel Reference Period

The travel reference period is 4am to 3:59am. This allowed the capture of information for respondents who finish work or return from leisure activities after midnight.

Travel Reference Day

To ensure that data was collected for all seven days of the week, each person participating in the NTS was assigned a selected 'travel reference day'. The travel reference day was a maximum of three days prior to the day on which the interview was conducted to ensure that recall was not compromised.

For interviews conducted on Wednesday through to Saturday, the travel reference day was the immediately preceding day, i.e. if a person was interviewed on Friday November 25th, the travel reference day would be Thursday November 24th.

For interviews conducted on Mondays a different arrangement applied. 30% of Monday interviews were assigned at random to the immediately preceding Friday, 42% to the immediately preceding Saturday and 28% to the immediately preceding Sunday.

For interviews conducted on Tuesdays, 17% were assigned at random to the immediately preceding Sunday and 83% were assigned to the immediately preceding Monday.

Degree of Urbanisation

This classification is created from an aggregation of population density estimates derived from the Census of Population. The categories included in each aggregate are explained below:

  • Thinly populated area refers to rural areas
  • Intermediate density area refers to towns and suburbs
  • Densely populated area refers to cities, urban centres and urban areas


The regional classifications in this release are based on the NUTS (Nomenclature of Territorial Units) classification used by Eurostat.  The NUTS3 regions correspond to the eight Regional Authorities established under the Local Government Act, 1991 (Regional Authorities) (Establishment) Order, 1993, which came into operation on 1 January 1994. The NUTS2 regions, which were proposed by Government and agreed by Eurostat in 1999, are groupings of the NUTS3 regions. The composition of the regions is set out below.

The composition of the regions is set out below.

Border, Midland and Western NUTS2 Region     

Southern and Eastern NUTS2 Region          




Dublin City




Dun Laoghaire-Rathdown








South Dublin
























Limerick City




Limerick County




North Tipperary


Galway City




Galway County










South Tipperary




Waterford City




Waterford County












Cork City




Cork County






QNHS Social Modules

While the main purpose of the QNHS is the production of quarterly labour force estimates, there is also a provision for the collection of data on social topics through the inclusion of special survey modules. The selection of the major national modules undertaken to date has been largely based on the results of a canvass of users (over 100 organisations) that was conducted by the CSO in 1996, 2002, 2006, 2008 and most recently 2011. The results of the canvass are presented to the National Statistics Board and they are asked to indicate their priorities for the years ahead.

The schedule for social modules in any given year is based on the following structure:

Quarter 1   Accidents and Illness module and  Information, Communication and Technology (ICT) Survey

Quarter 2   EU module (always covered under EU legislation)

Quarter 3   National module

Quarter 4   National module

Some of the social modules published to date in the QNHS are outlined below:

Irish Health Survey 2015

Q3 2015 Crime and Victimisation

Q2 2016 Households and Family Units

Q2 2016 QNHS Union Membership

Q4 2015 Pensions

Q2 2015 Households and Family Units

Q3 2014 Equality Module

Q2 2014 Environment Module

Q3 2013 Volunteering and Wellbeing

Q2 2013 Sport and Physical Exercise

Q3 2012 Effect on Households of the Economic Downturn

Q2 2012 Retirement Planning

Q2 2012 Parental Involvement in Children’s Education

Q2 2012 Union Membership

Q1 2012 Unemployment Thematic Report

Q2 2011 Response of Households to the Economic Downturn - Pilot Module

Q2 2011 Voter Participation

Q4 2010 Equality

Q3 2010 Health Status and Health Service Utilisation

Q2 2010 Cross Border Shopping

Q2 2010 Educational Attainment

Q1 2010 Crime and Victimisation

Q4 2009 Pension Provision

Q3 2009 Carers

Q2 2009 Union Membership

Q2 2009 Cross Border Shopping

Q3 2008 Lifelong Learning

Q4 2007 Childcare

Q3 2007 Health Status and Health Service Utilisation

Q3 2006 Sport and Physical Exercise


More historical social modules published are available at:

Participating Households

The Central Statistics Office wishes to thank the participating households for their co-operation in agreeing to take part in the survey and for facilitating the collection of the relevant data.