Chapter 1 Introducing the digital travel diary
Authors and Contact Details
Authors: Ella Gerlack, Alison Henderson, Anna Keyes, Iain Templeton, Matthew Wong
National Centre for Social Research
3rd Floor, Tiller and Lock
250 City Road
London EC1V 2AB
020 7250 1866
Prepared for: Department for Transport
1.1 Introduction and background
The National Travel Survey (NTS) provides up-to-date and regular information about personal travel within Great Britain and monitors trends in travel behaviour. The Ministry of Transport commissioned the first NTS in 1965 to 1966, and it was repeated on an ad-hoc basis in 1972 to 1973, 1975 to 1976, 1978 to 1979 and 1985 to 1986. In July 1988 the NTS became a continuous survey (that is, fieldwork was conducted on a monthly basis starting in January and ending in December) with an annual set sample size of 5,040 addresses. This increased to 5,796 by 2001 and to 15,048 addresses in 2002.
Since January 2002, the Department for Transport (DfT) has commissioned the National Centre for Social Research (NatCen), an independent social research institute, as the contractor for the NTS. NatCen is responsible for questionnaire development, sample selection, data collection and editing, data file production and building the database. The DfT is responsible for data analysis, publication, and archiving.
From its inception, the NTS has operated using a face-to-face (F2F) design. Under the F2F approach, initial contact with the selected addresses was made by an advance letter, sent through the post. This was then followed up with a visit to the address by a trained interviewer who attempted to encourage participation and for the household to complete a F2F in-home survey and 7-day travel diary, which was then collected by the interviewer from the respondent’s home. Following the onset of the COVID-19 pandemic in March 2020, F2F fieldwork was paused. The survey switched initially to a phone-based interview, then resumed doorstep recruitment and face-to-face interviewing from 2022.
Since the survey’s inception in 1965, the 7-day travel record has been administered exclusively on paper. Starting in 2025, the NTS adopted a digital-first approach to the collection of information on travel behaviour, offering respondents a digital diary as the primary mode of completion, with a paper option available for those unable or unwilling to use the digital format. This mixed-mode, digital-first approach aligns with broader trends in survey methodology, as more surveys shift toward digital modes to leverage technological advances and reduce logistical and environmental costs.
This chapter introduces the F2F updated methodology for 2025 particularly regarding fieldwork procedures for the digital-first approach.
1.2 Overview of changes in 2025 to incorporate the digital travel diary
Although introducing multiple survey modes offers clear advantages (including reduced logistical and environmental costs, increased participation), it can also introduce systematic differences in measurement that bias survey estimates. The digital diary was designed to mimic the paper diary, to reduce possible impact on the time series of the travel data.
The feasibility of an online travel diary was assessed through various testing phases from 2018 to 2024. During the discovery and alpha phases (2018 to 2020), a minimum viable product was developed and tested with interviewers, whose feedback led to refinements in the beta phase (2021). In this phase, the diary was tested with a few respondents who had previously used the paper diary. Following adjustments made based on feedback, the digital diary met Government Digital Standards through fulfilling technical requirements and securely handling data. A small-scale pilot was conducted in late 2022 with a sample of 100 addresses, leading to further modifications based on the pilot findings.
To evaluate the impact of the digital-first approach on key trip estimates and overall NTS fieldwork procedures, a large-scale parallel run of the two methodologies was carried out in early 2024. The digital-first approach did not substantially impact response rates, fieldwork performance, or processing procedures such as weighting and imputation. The key differences between the digital-first approach and the traditional paper-only approach are outlined below:
increased proxying in the digital-first group
evidence of lower trip reporting in the digital-first group, particularly short walking trips
difference in digital uptake across certain socio-demographic groups
For more details, see the full report of the digital diary parallel run, which outlines the findings.
Following the parallel run, it was agreed that the new digital diary would be introduced to the NTS in 2025. As a result of recommendations from the parallel run, detailed improvements to fieldwork procedures and training were implemented for 2025 giving a comprehensive strategy to enhance the efficiency and effectiveness of interviewers working on the digital-first diary approach. These changes supported the comparability of delivery of the two diary modes, of which the key initiatives were:
an automated onboarding system (using a QR code) was implemented to streamline the process of setting up households in the digital diary system and reduce human error
ensuring all interviewers have access to working mobile phones capable of reading QR codes; and providing appropriate training for these devices
mandatory pre-briefing sessions to ensure a basic level of technical literacy, including skills such as tethering phone signals, scanning QR codes, and accessing the internet on mobile devices
interviewers allowed to use respondents’ devices for onboarding
the CAPI questionnaire was adjusted so mixed-mode households were accommodated, to increase flexibility and the number of digital diaries received
an example page incorporated into the digital diary to guide respondents on how to record their trips
a dedicated NTS helpline was established, staffed by trained members of NatCen’s freephone team to offer rapid responses to interviewers’ queries while setting up households digitally. This team also monitored the support and feedback queries logged in the digital diary system from respondents and interviewers
a team of experienced NTS interviewers with excellent technical skills, also known as NTS “project champions” to provide personalised support to interviewers
Full details on the changes and improvements to the NTS fieldwork sequence are provided in Chapter 4.
1.2.1 The digital travel diary
The digital diary was developed from the paper diary and collects the same travel data. Although the data requirements are consistent across both modes, differences in their user interfaces result in different respondent and interviewer experiences. Both diary modes include guidance to support trip recording, but differ in how information is presented, accessed and recorded.
During the set-up stage, households using the digital diary were required to register at least one email address. For paper diaries, interviewers prepared the booklets and left them with the household. For both diary modes, interviewers were encouraged to use the practice page to demonstrate diary completion and enter examples of typical trips before respondents began recording their travel.
The digital diary offers a mobile-accessible, browser-based format with contextual guidance and features designed to reduce duplicate data entry, such as return, repeat and shared trip functions. It includes video guides, direct support links and a feedback centre to assist participants throughout their travel week. It also features pre-coded transport modes and routed questions, ensuring users only see relevant questions, such as parking or ticket cost screens. Trip summaries are displayed on the right-hand side of the screen, allowing participants to easily review trips they have already recorded.
The paper diary provides a physical record that allows respondents to view multiple trips and days at once and to refer to example and practice pages while completing entries.
Table 1.1 compares the key features of the digital and paper travel diaries from the respondent’s perspective.
Table 1.1: Differences between diary completion across diary modes for respondents in 2025
| Feature | Digital diary | Paper diary |
|---|---|---|
| Format | Online diary accessible through a web browser, with a mobile-optimised version | 16-page A4 stapled booklet |
| Portability | Accessible via mobile phone and can be completed while travelling or away from home. A separate memory jogger can be provided to support diary completion | Physical booklet that can be carried for recording trips throughout the travel week. A separate memory jogger can be provided to support diary completion |
| Prompts and guidance | Guidance, video guides and contextual help text are available throughout diary completion | Guidance is provided on the inside cover, with brief instructions included on each diary page |
| Viewing entries | All trips in one day can be viewed on a single screen, with trip summaries displayed on one side of the screen | Allows respondents to view all trips for a day and compare or reference entries across days of the travel week |
| Practice page | Accessible on the respondent’s diary overview page | Accessible at the back of the booklet |
| Example page | Accessible on the respondent’s diary overview page | Accessible at the front of the booklet |
| Trip entry features | Return, repeat and share trip features available to reduce the amount of data entry required | Repeated and shared trips can be cross-referenced, but return trips must be recorded as separate trips |
Note: For the 2025 survey year, respondents could not copy journeys entered on the practice day into their live diary. This functionality was introduced for the 2026 survey year, allowing respondents to copy journeys from the practice day directly into their live diary.
1.2.2 Overview of digital-first fieldwork
The task of completing the diary was explained to respondents with reference to the digital diary in the first instance. At the end of the placement interview, interviewers assist household members in setting up their access to the digital diary and ensure they can log in successfully. To access the digital diary, households were required to provide at least one email address. This was collected during the placement interview and entered into the digital diary system, enabling respondents to receive access details and log in to complete their diaries online. Paper diaries remained available for those unable or unwilling to take part digitally. Proxying was also allowed for both diary modes for those unable or unwilling to complete their own diary where the diary was completed by another household member, or in a few cases, by the interviewer. See section 4.9 for more details on placing and proxying of the travel diaries.
The digital diary includes some data validation measures, for example times must be numeric, and fields such as trip origin, destination, and purpose cannot be left blank. However, the digital diary does not contain automated checks to prevent impossible diary entries, such as two different journeys occurring at the same time, or no return journey. As with the paper diaries, quality control of the data was provided by the interviewer’s review of the diaries during the mid-week check and pick-up visit, and through robust post-hoc diary edit and checking procedures.
The procedures used for checking and editing diaries differed according to diary mode. In both modes, interviewers were encouraged to conduct at least one mid-week check with respondents to resolve queries and support diary completion. Table 1.2 summarises the main differences in the checking and editing processes.
Table 1.2: Differences between the interviewer checking and editing process across diary modes in 2025
| Process | Digital diary | Paper diary |
|---|---|---|
| Viewing diaries | Interviewers could remotely view respondents’ entries through the interviewer dashboard during the travel week | Interviewers reviewed diary entries directly from the paper diaries at the mid-week or pick-up visit |
| Household cross-checking | A dedicated household overview interface allowed interviewers to navigate between household members’ diaries and compare journeys | Interviewers typically laid out household members’ diaries side by side and cross-referenced journeys on a day-by-day basis |
| Making corrections | Required amendments could be noted using the interviewer notes feature. Corrections could be applied using household overview screen the impersonate feature | Corrections were made directly on the paper diary |
| Identification of interviewer edits | Changes made by interviewers were recorded within the digital system which were visible to the coders | Interviewer amendments were distinguished from respondent entries through the use of green ink |
| Final checking and data submission | After final checks, interviewers approved each diary then submitted the household. The digital diary data was transferred via an API from to NatCen’s Operations Department for coding | After final checks, interviewers posted paper diaries back to NatCen’s Operations Department for coding |
For further details on the mid-week check and pick-up call, see section 4.13 and section 4.14.
All other aspects of the NTS were consistent with previous years and did not undergo any changes for 2025, such as the sample strategy, methodology, and fieldwork delivery. Details on these aspects are outlined in the following chapters.