Chapter 2 Background
The 2025 NTS sample was increased for the 2025 survey year, which saw the sample significantly increase to 31,680 addresses. For the last 6 months of 2025, a reserve sample was issued, which was an additional 3,476 addresses to the core number of addresses, increasing the overall sample size for 2025 to 35,156 addresses. For further details on how the reserve sample was issued in 2025, see Chapter 3. The sample size was increased to allow more granular analysis, and also to ensure robustness in the key statistical estimates which are required from NTS data (see section 2.2 below for further details).
This chapter introduces the F2F methodology for sample design, fieldwork procedures, data preparation and data provision for the 2025 NTS.
2.1 Uses of the NTS data
The NTS is one of DfT’s main sources of data on personal travel patterns in Great Britain. The survey collects detailed information on the key characteristics of each participating household and any vehicles to which they have access. In addition, everyone within the household is interviewed and then asked to complete a 7-day travel diary, which followed a digital-first approach for 2025 with a paper diary available as a back-up. The survey therefore produces a rich dataset for analysis with information recorded at several different levels (household, individual, vehicle, long-distance journey, day, trip, and stage).
Data from the NTS is used extensively by DfT to monitor changes in travel patterns and to inform the development of policy. The findings and data are also used by a variety of other organisations, including:
- other government departments (such as HM Revenue and Customs, HM Treasury, the Department for Environment, Food and Rural Affairs)
- university academics and students
- transport consultants, local authorities and voluntary sector organisations representing a wide range of interests including motorists, cyclists, older people, rural communities and children
Table 2.1 below gives examples of the uses of NTS data with links to the relevant webpages.
Key results from the 2025 NTS are published by DfT in the statistical release National Travel Survey: 2025.
DfT deposit a non-disclosive version of the NTS dataset at the UK Data Service, which is available at the UK Data Service.
Table 2.1: Examples of the uses of NTS data
| Uses |
|---|
| To understand how and why people travel, including trip chaining, for the Department’s Better Connected strategy |
| To help forecast future trends in road traffic as part of the National Road Traffic Projections |
| To monitor the number of cycle stages per person per year for an indicator in the Department’s Single Departmental Plan |
| As an input into the Cycling and Walking Investment Strategy |
| To answer Parliamentary Questions and other Ministerial Correspondence, for example Roads: Accidents, Bus Services: Commuters |
| As a possible supplement to rail demand forecasting models in DfT |
| In the development of the National Cycling Propensity Tool for DfT |
| For monitoring road accident rates amongst different road users, especially pedestrians in the Road accidents and safety statistics |
| To understand how people travel to the shops and the impact of home deliveries in the Why people travel: Shopping factsheet |
| To examine travel among different groups, such as older people and people with mobility difficulties in the Disability and travel: 2007 to 2014 factsheet |
| To get information about users of modes of transport, for example in the Motorcycle use in England factsheet |
| To produce free annual reports that allow analysis of changes in personal travel over time |
| To study how children travel to school and how this has changed over time, in the Travel to school factsheet |
| To provide analysis and advice for around 300 direct requests to the DfT statistics team per year |
| To estimate annual pollutant emissions, including greenhouse gases and air quality pollutants |
2.2 Overview of sample selection
The 2025 NTS was based on a stratified, clustered random sample of private households in England, drawn from the Postcode Address File (PAF), as was the case in 2024 (see Chapter 3 for further details).
In 2025, the issued survey sample was 35,156 addresses, which was an increase from the 2024 sample size. Before 2023, the sample issue size was 12,852 addresses. As such, the sample size in 2025 was more than twice the size it was in 2022. This increase was done to facilitate more granular analysis of the data both geographically and demographically, such as allowing more analysis by specific protected characteristics.
2.3 Overview of fieldwork sequence
Historically, the NTS has used 2 data collection methods:
F2F interviewing using computer assisted personal interviewing (CAPI) on interviewer laptops
self-completion of a 7-day travel record (issued as a digital diary with a paper diary as a back-up)
The overall sequence of tasks, from the initial sample selection to data analysis and reporting was as follows:
Sample selection from the Postcode Address File (PAF).
Questionnaire development and fieldwork preparation.
Fieldwork.
Data transmission and documents returned by interviewers.
In-house data input and editing.
Quality checking.
Data checking using SPSS.
Data file production, variable derivation and imputation and delivery to NTS.
Data analysis and reporting by NTS.
In 2025, the phone back-up option (PB) was only used when F2F was not possible, primarily for households where participants were unable to participate due to having a suppressed immune system. Of the 11,021 productive households, 378 were PB cases (figures are unweighted and include cases with missing weighting information).
This PB fieldwork approach broadly followed the same fieldwork sequence as F2F. The introduction of the digital diary allowed respondents who need to use this approach to self-complete a diary compared to previous years where the paper diary had to be completed by the interviewer.
Fieldwork sequence for F2F:
Sampled addresses issued to interviewers.
Advance letters posted (by interviewers).
Make contact at the address and organise interview.
Placement interview conducted in person, and travel diary placed with household.
Travel week starts, as per ‘fixed travel week’ allocation method.
One mid-week check (in person or by telephone).
Travel week ends.
Pick-up interview in person.
Return work and transmit data.
Fieldwork sequence for PB:
Sampled addresses issued to interviewers.
Advance letters posted (by interviewers).
Make contact at the address with the intention of arranging a F2F interview. If someone in the household was immunosuppressed, a telephone interview would be arranged instead.
Placement interview conducted via telephone, and travel diary task introduced to the household.
Travel week starts, as per ‘fixed travel week’ allocation method.
If the household was set-up on a digital diary, at least one mid-week check was conducted. If the interviewer was completing on their behalf, 2 mid-week checks were conducted, with interviewer populating a couple of days of the travel diary at each check.
Travel week ends.
Pick-up interview via telephone including populating remaining days of the travel diary.
Return work and transmit data.
2.4 Overview of fieldwork procedures
Interviewer points (also known as assignments) were distributed evenly across a quarter, whilst the individual start dates for each point were spread out across each month. The aim of this approach was to obtain a balanced and representative response to the survey across the whole year (see sections 3.7 and 3.8 for further information).
The fieldwork sequence is outlined in section 2.3 and began with the interviewer sending advance letters to their sampled addresses. These letters briefly explained the purpose of the NTS and mentioned that an interviewer would contact them. It also stated that each respondent would receive a shopping voucher as a thank you, if all household members completed the survey.
From June 2004 to December 2024, a book of first-class stamps was included with the advance letter as a gesture of goodwill to encourage respondents to take part. In 2025, the stamps were replaced with a £10 Post Office voucher which was printed as a barcode on the bottom of the advance letter.
Interviewers followed up the advance letter by making in-person contact with the household to arrange a placement interview. The start date of their point determined when they could first go into field to make contact. The placement interview gathered information about the household, its individual members, household vehicles and long-distance journeys that the household members had made in the last week. At the end of the placement interview, the interviewer explained and placed the 7-day travel diaries, allocating a travel week using the ‘fixed travel week’ method.
The ‘rolling travel week’ approach (whereby the travel week always started on the day before the placement interview) has been retained in 2025 as a fallback option, only used in exceptional cases where the interviewer has been allocated their point late into the fieldwork period, and permission must be sought to use them.
If respondents agreed to it, they were sent an automated text reminder on the morning of the first day of the travel week to remind them to start completing their diary. If there was a gap of more than a few days between the placement interview and the start of the travel week, interviewers were expected to make a reminder call or visit or delivered a reminder card to the household to remind them that their travel week was about to start. This was followed by a mid-week check call (either by telephone or F2F) during the travel week to check on the household’s progress in completing their diaries.
After the travel week (and ideally within 6 days) a pick-up interview was conducted. The digital diaries were checked. Paper diaries were collected, checked, and posted back to the Data Operations team at NatCen. The pick-up interview was also used to complete any outstanding sections of the placement interview and to check whether any key factors had changed since the placement, such as the purchase of a new car. At the end of the pick-up interview, the interviewer would administer a £5 shopping voucher conditional on a fully completed placement interview and a fully completed diary for each member of the household.
2.5 Overview of data input and editing
The CAPI data was transmitted back to the NatCen operations department, usually on the day after the pick-up call. Once the digital diaries were marked as complete by the respondent, the interviewer approved each diary and submitted the household on the digital diary system. Once submitted, the diary data was transferred from the digital diary supplier to NatCen via an API. Any paper documents were returned by interviewers by post. Once the data and any documents had been received, a team of NTS coders booked the diaries into the system. They then coded, keyed and edited the travel diary information using the Diary Entry System. The contents of the CAPI questionnaire were edited and checked, and all interviewer notes examined. The interviewers were contacted if there were any queries that could not be resolved by the coders. If necessary, the interviewer re-contacted respondents to resolve any issues, although this would be rare given the burden on the respondents.
Quality checks were also made on selected interviewers on a rota basis and 10% of addresses were back-checked (please see section 4.19 for more information).
2.6 Overview of data file structure
The data were organised into different levels, namely:
households
individuals
vehicles
long-distance journeys (made in the 7 days before the placement interview or before the travel week which ever date was earliest)
journeys made during the travel week and days within the travel week
stages of these journeys
Lastly, NatCen provided DfT with Primary Sampling Unit (PSU) level variables associated with each household, but which were not collected directly from households.
2.7 Quality of F2F fieldwork
The rate of interviewers making reminder calls or leaving a reminder card was 60% in 2025 compared to 55% in 2024 and 66% in 2019. Additionally, 94% of interviewers made mid-week checks in 2025 compared to 75% in 2024 and 77% in 2019. This change was largely driven by the introduction of the digital diary, which enabled interviewers to review diary entries remotely and conduct checks by phone.
The trip rate for all cases was 12.79 in 2025 compared to 13.79 in 2024 and 14.36 in 2019. This means there was a reduction of 1 trip per week in 2025. The no travel rate was 4.1% in 2025, which was consistent with 2024 and lower than the 2019 rate of 4.3%.
In 2025, there was a much higher proportion of interviewers who had worked on NTS in the last year (90%) compared to 2024 (85%), showing growing experience across the fieldwork team. For some indicators which are very similar to pre-pandemic levels this is likely supported by this greater interviewer experience.
2.8 Overview of survey response
Only households classed as ‘fully co-operating’ are included in the response calculations. Based on this, a national response rate of 28% was achieved in 2025. See section 4.16 for a definition of ‘fully co-operating’ and for full response details.
Overall, this is equivalent to an achieved sample rate (ASR) of 26%. The ASR includes those households classified as ineligible in the denominator.
As seen across all large-scale random probability F2F surveys, response rates in 2025 remained significantly below pre-pandemic levels. This is driven by 2 main factors. Firstly, refusal rates are higher now than they were pre-pandemic. Before 2020 around a third of selected households declined to take part in the survey. Since F2F fieldwork returned in April 2020 this has increased to around half. Secondly, on-going challenges that survey organisations face in re-building their fieldworker capacity since the pandemic mean that it is not always possible to issue all selected sample points to interviewers. In 2025, 6% of selected sample points were unworked.