Accredited official statistics

Chapter 3 Fieldwork procedures and response rate

Published 27 August 2025

Applies to England

Introduction

The NTS is a continuous survey with fieldwork taking place throughout the year. Throughout 2024, traditional doorstep recruitment was used, preceded by the interviewers sending out an advance letter to each household. For the second quarter of 2024 an experiment took place where a £10 shopping voucher was trialled alongside the £5 shopping voucher. See section 3.15 for more details on the shopping voucher for respondents and the incentive experiment.

While F2F was the primary approach, interviewers could also offer a telephone interview as back-up in cases where COVID-19 was a concern. This was known as the phone back-up (PB) option. The travel records (also known as diaries) were filled in by the respondents themselves, except for PB cases for whom the diaries would instead be filled in by the interviewers over the telephone.

The ‘fixed travel weeks’ allocation method was in use, whereby interviewers would provide a household with a specific week in which to record their travel in the diary. This methodical allocation process was designed to ensure a relatively even spread of travel week start days over (a) the dates of the month and (b) the days of the week, due to the random element that was central to the allocation method. The first travel week available for allocation was staggered approximately 12 days after the interviewer was scheduled to start doorstep recruitment, to allow enough time to contact addresses and conduct placement interviews prior to the travel weeks starting. Interviewers were required to make one mid-week call for initial checking of the diaries that the F2F respondents were filling in, and 2 mid-week calls for PB cases.

The computer assisted personal interviewing (CAPI) questionnaires on the interviewer laptops were designed and implemented using the software system Blaise. A single Blaise instrument was used for the household, individual, vehicle and administrative sections of the questionnaire.

A separate Diary Entry System (DES) was written in Visual Basic. Selected CAPI variables were extracted and loaded into the NatCen field management system from where they were referenced by the DES. This process provides contextual information from the CAPI interview for those people inputting and editing travel diary data.

Note: for this chapter, comparisons of the 2024 data against 2023 data and 2019 data are included, as data from the pandemic years (2021 and 2020) was atypical for the NTS time series, and the methodology for 2022 remained different for part of the year, whereas 2019 continues to provide a robust baseline.

Interviewer briefings

In 2024 there were 2 types of briefings. New interviewers were briefed by NatCen’s research team during a series of 2-day online briefings (one briefing was held in person, but this approach was less flexible for people coming from across England and was not used in general). The briefings covered all aspects of the survey, including the demonstration of a dummy interview in the CAPI program, as well as role-play exercises to practise doorstep technique and the placing and picking up of the travel diaries. Interviewers were also given a pre-briefing exercise. This involved completing a travel diary themselves using their own journey details for the days preceding the briefing, studying the definitions manual, and completing a short test on how the diary should be filled in and the type of probing needed to gain the required level of accuracy and specificity.

Interviewers who had completed a NTS point (also known as an assignment) over the previous 12 months attended a half-day in-person refresher briefing shortly before the start of the survey year. This involved training on any changes that were new for the 2024 survey, a reminder of the fixed travel weeks allocation method, and using the new electronic Address Record Form (eARF).

Questionnaire and document despatch to interviewers

The Operations Department made the sampled addresses and the CAPI questionnaire available to the interviewers for download onto their laptops via a secure broadband connection before the start of each quota month. The relevant NTS materials were despatched to the interviewers by post.

Any queries about transmission or other technical matters were dealt with by a helpline run from the Operations Department during working hours. Laptop maintenance was handled by a separate IT support department within NatCen. Interviewers had the support of their launch supervisor, an experienced NTS interviewer who accompanies new interviewers when they first go out in field door knocking and interviewing. The interviewers were also able to contact staff within the Operations Department who deal with the administration of fieldwork.

Interviewer start dates and points

Interviewers were assigned to start fieldwork on different dates to ensure that interviewing was evenly spread across the year. The same principle applied to the travel week start dates, ensuring that the data recorded in the travel diaries was also spread evenly across the year, which is further underpinned by the fixed travel week allocation method used.

Interviewer points were allocated evenly across a quarter, rather than by month. When allocating points to quota months it is done in such a way a naturally representative sample is distributed for each quarter. See sections 2.7 and 2.8 for further information.

Contacting respondents

Interviewers were given advance letters to send to the selected addresses ahead of their first doorstep call (see Appendix B). For NTS 2024, the advance letter broadly mirrored the NTS 2023 advance letter. The only change made was removing text that mentioned the option to participate in a telephone interview from the ‘Frequently Asked Questions’ page on the rear side of the letter.

The advance letter gave some general background to the survey and explained its importance, some of its uses, and how the household had been selected. It also stated that each respondent would receive a £5 shopping voucher if all household members completed the survey.

The letters included a space for interviewers to write in their name so that respondents knew who would be calling and to make the letters more personal. As has been the case since June 2004 onwards, a book of first-class stamps was included with the advance letter as a gesture of goodwill to encourage respondents to take part.

Interviewers were notified of any refusals made to the Operations Department as a result of the advance letter being responded to by the residents of the sampled address. Interviewers were not required to visit these addresses and they did not count against interviewers’ individual response rates. However, they were classified as non-response (office refusals) in calculating the overall response to the survey.

A few days after the advance letters had been sent, interviewers contacted respondents by personal visit. Interviewers were required to make a minimum of 6 calls (that is, personal visits to the address) and to make sure that the days and times of these calls varied to maximise the chance of making contact with the selected household. If there was still no contact, only then could an interviewer return a case as a ‘non-contact’. Interviewers were also given a non-contact letter (which has been in place since November 2008) to post through the door of addresses where contact could not be made after 5 or 6 attempts (see Appendix C). The non-contact letter offered the household a further opportunity to learn about the NTS and to let NatCen’s Operations Department know if they wanted to take part. The changes that were made to the advance letter for NTS 2024 were also mirrored in the non-contact letter where relevant.

As in previous years, interviewers were also given information leaflets about the study (see Appendix D) and the NTS 2023 Factsheet so that, when necessary, they could demonstrate to respondents the type of data collected by the NTS. This was intended to help boost response and make the survey easier to sell on the doorstep.

Confidentiality

Respondents were informed in the advance letter that their participation was voluntary and that any information they provided would remain confidential and would not be passed on to anyone outside NatCen or the statistics section at DfT in a form that could be used to identify them. Respondents were provided with a telephone number and an email address for NatCen’s Operations Department that they could contact if they had any queries. Any substantive queries or complaints were subsequently passed on to researchers to deal with.

The placement interview

The first stage of interviewing consisted of the placement interview, using the CAPI questionnaire. This was conducted with all household members and consisted of 3 sections.

The household questionnaire was asked of the Household Reference Person (HRP), which is the householder with the highest income, or their spouse or partner. In exceptional cases the household questionnaire could be asked of another responsible adult aged 16 or over.

The individual questionnaire was asked of each household member, including children (although proxy information was always collected for children under 11 years old). A maximum of 10 people could be included. On the extremely rare occasions when interviewers encountered a household with more than 10 members, they were instructed to select the oldest 10 to take part in the interview, and to ensure that all vehicle owners were included.

The vehicle questionnaire was asked of the main driver for each vehicle in the household. A maximum of 10 vehicles could be recorded.

The percentage of individuals in 2024 who were interviewed in-person or by proxy for the placement interview (as well as those not interviewed) is shown in Table 3.1. The table is broken down by age into the 2 main age groups:

• those aged under 16 (defined as a ‘young person’)

• those aged 16 or over (defined as an ‘adult’)

Comparable figures for 2023 and 2019 are shown in Tables 3.2 and 3.3.

Table 3.1 shows that a high proportion of the individuals aged 16 or over were interviewed in-person in 2024 (68%), which is very similar to the proportion interviewed in-person in 2019 before the pandemic (70%) as shown in Table 3.3. The vast majority of individuals aged under 16 were interviewed by proxy in 2024 (96%), which is higher compared to the proportion interviewed by proxy in 2019 (85%). In 2024, a hard check was added into the (CAPI) questionnaire to ensure that no individuals aged under 11 were being interviewed in-person which explains the increase in proxy rates for individuals aged under 16.

Note: figures in the tables may not total 100% due to rounding.

Table 3.1: Method of individual interview at placement, by age (2024)

Method of interview	Aged under 16 (young person)	Aged 16 or over (adult)	Total
In-person	2%	68%	57%
Proxy	96%	31%	42%
Not interviewed	2%	1%	1%
Base (individuals)	3,490	17,122	20,612

Table 3.2: Method of individual interview at placement, by age (2023)

Method of interview	Aged under 16 (young person)	Aged 16 or over (adult)	Total
In-person	11%	69%	59%
Proxy	86%	30%	40%
Not interviewed	3%	2%	2%
Base (individuals)	3,032	14,351	17,383

Table 3.3: Method of individual interview at placement, by age (2019)

Method of interview	Aged under 16 (young person)	Aged 16 or over (adult)	Total
In-person	15%	70%	59%
Proxy	85%	30%	41%
Not interviewed	0%	0%	0%
Base (individuals)	3,163	12,920	16,083

The 2024 NTS questionnaire

Each section of the placement interview covered a number of different topics:

The household questionnaire included:

• the household grid

• questions about home deliveries and food shopping

• questions about children’s travel to school

• the household vehicles grid

The individual questionnaire included questions about:

• disabilities that affect travel

• methods of transport used

• walking

• cycling

• e-scooter

• driving licences

• internet use

• (self-completion section) satisfaction with transport services, and perceptions of one’s own social isolation

• education, paid work and journey planning

• last paid job

• income

• location of work

• travel to work

• working at home

• ease or difficulty of travelling to work

• transport difficulties

• road accidents involving adults

• road accidents involving children

• special tickets or passes

• long-distance journeys

• permission for re-contact for follow up

The vehicle questionnaire included questions about:

• the vehicle registration number

• vehicle details

• parking

• mileage

Note: The coding of Standard Occupational Classification was carried out in 2024 according to the 2020 system.

The questionnaire specification is provided in Appendix A3, and an overview of how to interpret the questionnaire specification is provided in Appendix A1. Additionally, the questionnaire show cards are provided in Appendix H for reference.

Long-distance journeys

The NTS collects details about any long-distance journeys, defined as trips of 50 miles or more made within Great Britain. Where journeys of this type occur during the allocated travel week, these are simply recorded in the travel diary as usual.

Additionally, respondents are asked about long-distance journeys in the placement interview itself, but relating to a different (earlier) 7-day period. The week for which respondents were asked about long-distance journeys was normally the 7 days preceding the placement interview. However, in cases where the travel week was allocated to start date before the placement interview, the 7 days were instead taken to be the week preceding the start of the travel week. In total, a maximum of 40 long-distance journeys could be recorded during the interview.

Changes in 2024

The changes made to the NTS questionnaire in 2024 were as follows:

• change in the administration of the ‘sex’ question located at the beginning of the Household questionnaire, so this is now asked instead of being coded from observation by the interviewer

• new questions about vehicle ownership have been added to the Vehicle grid in the Household questionnaire, about how people got their vehicles, including if they were received as a gift

• new questions about vehicle chargepoints and charging (for electric/battery only vehicles and plug-in hybrid vehicles) have been added to the Vehicle questionnaire

• an older question about important factors when buying a car or van was reintroduced to the Computer Assisted Self-Interviewing (CASI) section with some updates to the response options

• minor changes to the ‘ethnicity’ answer options

All changes to the questionnaire for 2024 are detailed in Appendix A2 and a summary of all questionnaire changes since 2002 is provide in Appendix A4.

Rotated questions

From 2002, some questions were designated to be ‘rotated’, such that they would be asked every other year. For 2024, the biennial rotating questions in Module A (even years questions) were asked, and the questions in Module B (odd years questions, last asked in 2023) were taken out. Some questions that previously appeared on a 2-year rotation are now being asked every year for 2024 onwards to find out what items the household might have ordered online and how often.

The 2024 survey also included questions that appear on a 4-year rotation. These were last asked in 2020, and will next be asked in 2028, and so on. One question that previously appeared on a 4-year rotation is now being asked every year for 2024 onwards to find out how long the (HRP) has lived at the address.

Module A (even years) included questions about:

• cycling:
  Barriers to cycling; and what would encourage more cycling

• driving licenses:
  Reasons for not driving currently among those with a licence; reasons for no longer holding a licence; and age last drove

• ease or difficulty of travelling to work:
  Difficulties with travelling to or from work by car, van, motorbike, scooter, or moped or by public transport; how easy is it to make journey to work, not using a car, van, motorbike, scooter, or moped; and what method of transport would they use instead

• transport difficulties:
  Type of transport respondent has difficulty with:

  • difficulties when travelling to the doctor’s surgery or hospital

  • difficulties experienced when visiting friends or relatives or other social activities

  • difficulties experienced when taking children to school or university

  • difficulties experienced when travelling for other purposes

• parking:
  Location of parking for vehicles

• mileage:
  Purpose and miles driven outside of Great Britain

For reference, Module B (odd years) included questions about:

• food shopping:
  Usual method of food shopping

• children’s travel to school:
  Barriers of children walking to school more and what would encourage more walking to school more; and reasons for travelling to and from school with an adult

• disabilities that affect travel:
  Use of powered or manual wheelchair and how often it is used; whether a respondent is a carer and time spent caring; and prevalence of special transport services and usage of any of these special services

• walking:
  Barriers to walking more and what would encourage more walking in local areas

• driving licenses:
  Reasons for not driving among those without a provisional licence; and likelihood to learn to drive

• travel to work:
  Types of road used to travel to work; are respondents the driver or passenger travelling to work and how often is a lift given or received; and place of parking when driving to work

• working from home:
  Days of the week normally working from home; and extent to which it is possible to work from home and how much can be completed from home

4-year rotation questions included:

• tenure:
  What type of accommodation does the household live in

• carpooling:
  Whether the household use cars from a company car-pool

• transport related barriers to work:
  Whether the respondent has turned down a job or decided not to apply for a job they were interested in due to problems with transport and if so what problems these were

• travel to work questions:
  Reasons why respondent walks to work; and reasons why respondent cycles to work

Self-completion questions

Since 2017, attitudinal questions were asked of one member of the household aged over 16, administered by Computer Assisted Self-Interviewing (CASI). This member was randomly selected by the Computer Assisted Personal Interviewing program among the adults of the household present during the interview (proxy respondents could not be selected). See section 2.6 for more details on how the random selection was made.

The respondent completed the section on their own, using the interviewer’s laptop. The questions asked about (a) the respondent’s satisfaction with transport services, and (b) their own perception of how socially isolated they were. In 2024, an older question was reintroduced to the Computer Assisted Self-Interviewing (CASI) section with some updates to the response options, to find out what is important to respondents when buying a car or van.

Harmonised questions

A number of harmonised questions are used in the NTS to allow users of the data to compare NTS data with those from other social surveys. These questions are listed in Table 3.4, with the harmonised question name shown against the equivalent NTS question name. The final column of the table shows when the question was introduced into the survey and also provides additional information if the question has changed since that time.

Table 3.4: Harmonised questions used in the 2024 NTS

Harmonised question name	NTS question name	Year introduced
Sex	Sexfw	2024 (question was updated in 2024 from an interviewer coded question to a show card question with the response options re-ordered. The 1998 ‘Sex’ variable continues to exist as a background variable in Blaise.)
Age	AgeIf	1998
Date of birth	Birth	2000
Marital status	MaritalStat	2013, with answer categories amended in 2023
Living arrangements	LiveWithN	2013
Ownership of accommodation	Hhldr	2002, with answer categories amended in 2003
Joint ownership	HiHNum	2002
Ethnic group	EthGroupB	2001, with answer categories amended in 2024 and headings for answer categories amended in 2022
Length of residence	HLongA	1998
Relationship to head of household	RelHoH	1998 (question now asked as relationships of household members)
Relationships of household members	Relation	2013, with answer categories amended in 2013
Religion	Religion	2022
Accommodation type	Accom	2000
House type	HseType	2000
Flat type	FltTypN	2000
Other accommodation	AccOth	2000
Housing tenure	Ten1	1998, with answer categories amended in 2013
Car ownership	UseVcl	1998, with answer categories amended in 2003 and question text amended in 2004
Vehicle type	TypeVcl2	1998, with answer categories amended in 2003 (question was deleted in 2004, and has since been imputed using TypeVcl2)
Company car	PrivVcl	1998, with question text amended in 2009
General health	GenHeal	2017
Length of residence	HLongInd	2017
Home deliveries	Deliv1 and Deliv2	2024
In employment	Wrking	1998
Training scheme	SchemeET	1998
Away from work	JbAway	1998
Own business	OwnBus	1998
Relative business	RelBus	1998
Looking for work	Looked	1998
Starting work	StartJ	1998
Inactive	YinAct	1998
Industry	IndD	1998
Job title	OccT	1998
Job description	OccD	1998
Job status	Stat	1998
Paid employment	EverWk	1998
Date of leaving last job	DtJbl	1998
Supervising employees	SVise	2001
Organisation size	EmpNo	1998
Self-employed	Solo	1998
Number of employees	SENo	1998, with answer categories amended in 2003
Full or part time work	FtPtWk	1998
Long-term unemployed	HowLong	2004
Educational qualifications	EdAttn1	2005
Professional or vocational qualifications	EdAttn2	2005
Highest qualification	EdAttn4	2005
Internet access	OnlineN	2013, with answer categories amended in 2013
Important factors when buying a car or van	CarStyle	2024
Well-being	LackComp	2019
Well-being	LeftOut	2019
Well-being	Isolated	2019
Well-being	Lonely	2019
Disabilities that affect travel	Heallll	2018
Disabilities that affect travel	ImpCat1 to ImpCat10	2018
Disabilities that affect travel	LimitAct	2018

Length of the placement call

The average length of the placement call (that is, the placement interview plus the time taken to explain and, where necessary, complete the first days of the diary) for all households was just under 56 minutes in 2024, and varied according to household size, as shown in Table 3.5. Comparable figures for 2023 and 2019 are shown in Tables 3.6 and 3.7. These tables show the average time for different household sizes and the base figures for each row are also shown for reference in the final column.

As expected, Table 3.5 shows that the mean length of the placement call in 2024 tended to be longer for larger households, although the increase in time for each additional household member was not linear. For example, the mean length for a single-person household was 43.88 minutes, and then 57.36 minutes for a 2-person household and 61.24 minutes for a 3-person household. The longest mean time was 110.40 minutes for households with 9 people.

While some of the mean lengths have increased slightly in 2024 compared to 2023 and 2019 as shown in Table 3.6 and Table 3.7 respectively, most of the figures remain broadly in line with the previous year and pre-pandemic. For example, the mean length in 2019 was 40.41 minutes for single-person households and 54.77 minutes for 2-person households, which is slightly lower than 2024. However, the mean length in 2019 was 60.69 minutes for 3-person households and 64.04 minutes for 4-person households, very close to the mean length in 2024 . The slight increase in the average length of the placement call can be explained by the additional questions in the questionnaire due to including the 4-year rotation questions.

Table 3.5: Mean length of placement call (in minutes), by household size (2024)

Number of people in household	Mean length (minutes)	Base
1	43.88	2,804
2	57.36	3,722
3	61.24	1,346
4	65.21	1,187
5	67.59	389
6	74.91	115
7	91.89	36
8	67.73	11
9	110.40	5
10	78.33	3
All households	55.74	9,618

Table 3.6: Mean length of placement call (in minutes), by household size (2023)

Number of people in household	Mean length (minutes)	Base
1	41.49	2,212
2	55.11	2,946
3	57.26	1,094
4	61.88	922
5	65.74	282
6	66.97	95
7	75.60	30
8	53.17	6
9	68.33	3
10	132.20	5
All households	52.95	7,595

Table 3.7: Mean length of placement call (in minutes), by household size (2019)

Number of people in household	Mean length (minutes)	Base
1	40.41	1,879
2	54.77	2,522
3	60.69	968
4	64.04	958
5	65.23	273
6	69.08	79
7	71.79	24
8	69.50	6
9	80.20	5
10	89.33	3
All households	53.63	6,717

Allocation of Travel Weeks

Respondents were required to record their journeys in the travel record for a period of 7 days (the period known as the travel week). Interviewers were given pre-selected lists of travel weeks, and from these lists the travel weeks were allocated to households by the interviewers using a methodical and unbiased process whenever they reached a definitive outcome.

To achieve this, each quota month was assigned a non-overlapping sequence of 30 to 31 travel week start dates. Individual interviewers were given a bespoke list (the ‘Travel Week Allocation Card’) of 22 travel week start dates, each of which was selected at random. This was achieved in such a way as to ensure, as far as possible, that an equal number of travel weeks would begin on each day in that month’s sequence (that is, evenly spread across all the interviewers working on a point belonging to that particular quota month). This means that it was possible to capture not only variations in travel behaviour within a month, but also differences across days of the week.

Because the number of trips that respondents record often falls away as their travel week goes on, the selection and allocation processes have been designed so that an approximately equal number of travel weeks start on each of the 7 days of the week. If, for example, all travel weeks were to start on Mondays, results would be biased toward travel behaviour on Mondays, Tuesdays and Wednesdays, whereas Saturday and Sunday travel behaviour would be under-represented.

Interviewers working on the 2024 survey were instructed to use the traditional ‘fixed travel week’ allocation method. This meant assigning the first travel week in their Travel Week Allocation Card list to the first address at which they reached a definitive outcome. They would then assign the next travel week on their list to the second address at which they reached a definitive outcome, and so on.

This method was applied universally, with the exception that when interviewers had to allocate a travel week that was in the past in relation to the interview itself they would therefore need to skip any travel weeks that started more than 2 days before the interview, and instead allocated the first travel week available on their list that started within 2 days before the interview. This exception exists to minimise the risk that respondents forget to include journeys or forget the specific details of journeys because the travel took place too far in the past for them to remember correctly. However, typically most travel weeks would start in the future in relation to the interview, especially if the interviewer had started their fieldwork as early as possible and did not suffer any unforeseen delays to their fieldwork progress.

Definitive outcomes include all the non-productive outcome types, such as deadwood addresses, refusing households, and any other type of non-participating address. For participating households, a definitive outcome was reached (that is, for the purpose of allocating a travel week) when the interview began, and not before, so as to avoid allocating travel weeks to households who eventually break interview appointments. The CAPI program prompted the interviewer to enter the allocated travel week at the very beginning of the interview.

Allocating travel weeks in this methodical manner, including to the non-participating addresses, is the best way to ensure the travel records of the participating households cover the entire survey period evenly. It also avoids biasing the spread of diary data collection that would occur if the respondents were to choose the travel week themselves.

The ‘rolling travel week’ approach (whereby the travel week always started on the day before the placement interview) was introduced in 2020 to replace fixed travel weeks as it was not possible to control for the timing of the placement interview as part of the push-to-telephone methodology. It was retained in 2024 as a fallback option, only used in exceptional cases where the interviewer had been allocated their point late into the fieldwork period, and permission was required to use them.

Placing the travel diary and other documents

For 2024 the approach for placing the travel diary and other documents followed the traditional NTS F2F pre-pandemic approach. This approach involved the interviewer introducing and placing the documents at the end of the placement interview with the intention that the respondents would fill in the documents themselves. The 7-day travel diaries (see Appendix E) were placed for each household member, and the mileage charts (see Appendix G) were placed for each household vehicle.

For PB cases, the interviewer completed the 7-day travel diary with the respondent, collecting the information from them over the phone and populating the paper version on behalf of the respondent.

The 7-day travel diary

Everyone in the household was eligible to complete a 7-day travel diary in which their travel activity was to be recorded, completed either by the respondent themselves, by a proxy within the household, or by the interviewer (depending on the methodology used for the interview). There are 2 versions of the travel record:

• one for adults (respondents aged 16 and over)

• one for children (the young person’s travel diary, aged 15 or younger)

Each trip was recorded, and details of origin and destination, purpose, mode, distance travelled, time, number travelling in their party, vehicles used, tickets used and cost was collected. In addition, the adult version of the travel diary collected details about of any parking costs as well as indicating whether they were a passenger or driver.

For F2F cases, interviewers explained to respondents in detail how to complete the travel diary. They generally did this by entering the details of some typical journeys made by the respondent in the blank pages provided, often using the respondent’s previous day’s journeys. Some interviewers referred to the NTS definitions manual to help describe the level and type of details required. Since 2014, interviewers have also been provided with a list of key points to cover when placing and checking a travel diary.

For PB cases, interviewers collected information from respondents via telephone to populate the travel diaries. Therefore the need to explain the nuances of completing the diary was lessened for PB cases, since the interviewer would simply probe the respondent for the necessary level of detail required as they were populating the diaries.

Note: All survey definitions are given in the NTS definitions manual, copies of which are available on request.

Simplified pocket size diaries or memory joggers (see Appendix F), into which respondents could briefly note down their journeys, were placed with F2F respondents if the interviewer felt they would be helpful, and were placed with all PB respondents so that they could make notes about their travel which they could later refer to when explaining their travel to the interviewer over the phone. The memory joggers however did not replace the need for a diary to be completed, they were simply provided as a note-taking aid.

The travel diary was redesigned in 2007 following an extensive development study. Full details of this study are available on the Department for Transport’s website. For further detail see McGee A, Gray M and Collins D (2006), NTS Travel Record Review Stage 1; and see McGee A, Gray M, Andrews F, Legard R, Wood N and Collins D (2006) NTS Travel Record Review Stage 2.

Minor revisions were made to the diary in the following years

Table 3.8 Minor revisions to the travel diary

Year	Minor revision
2009	More rows added to the diary to record journeys, and text added to remind respondents to record short journeys
2013	Removal of diary elements related to cost of road tolls, congestion charges and taxi sharing
2017	Short walking day for recording walks of under one mile was changed from Day 7 to Day 1

A full list of changes that have been made to the travel diary since 2002 can be found in Appendix A4.

For 2024, the travel diaries collected information on:

• purpose of journey

• time left

• time arrived

• origin: where the journey started (from village, town or local area)

• destination: where the journey ended (to village, town or local area)

• method of travel (car, bus, walking)

• distance (in miles)

• time travelling (in minutes)

• number of people in party travelling

• which car or motorcycle was used (if journey was made by private transport)

• ticket type: single, return or travel card (if journey was made by public transport)

• cost (if journey was made by public transport)

• number of boardings: the number of trains or buses. used to reach journey destination (if journey was made by public transport)

On Day 1 of the travel week, information was collected on all walks over 50 yards. However, on Days 2 to 7, only walks that were one mile or more were recorded (approximately equivalent to taking 20 minutes or more).

Additionally, the adult travel diaries (for those aged 16 or over) collected information on:

• whether the respondent was the driver or the passenger (if journey was made by private transport)

• how much was paid for parking (if journey was made by car or motorcycle for example)

The young person’s travel diaries (for those aged under 16) also collected additional information on the number of people in party travelling, by splitting out the party into the number of adults and the number of children (whereas in the adult travel diaries only the total number of people was recorded).

The mileage chart

In addition to the diaries, a mileage chart was placed at the end of the placement interview for each household vehicle. The driver was encouraged to keep this chart in their vehicle. The chart required the driver to record the milometer reading at the start and end of the travel week. For the small proportion of PB cases the mileage chart was provided to respondents as part of the doorstep recruitment stage.

See Appendix G for a copy of the mileage chart.

The reminder call

Once the travel diary has been placed, the next stage is to remind the household to start recording their journeys on the date allocated to them, as the allocated travel week would in most cases start on a date after the placement interview. Interviewers did this either by either making a reminder call visit to the household (or leaving a reminder card if the household was absent at the time the interviewer made the visit) or by making a reminder phone call. Reminder calls would usually take place 1 or 2 days before the start of the travel week and were used for both F2F and PB cases in 2024.

The mid-week check call

Interviewers were strongly encouraged to conduct a call halfway through the travel week for F2F cases, to motivate respondents and help them with any difficulties they might be having filling out their travel diaries. This could be either a phone call or a personal visit and was at the interviewer’s discretion, although they were encouraged to conduct an in-person check, especially for elderly participants.

For PB cases, the mid-week check was used by interviewers to complete several days of the travel diaries on the respondent’s behalf, and interviewers were strongly encouraged to conduct this over 2 calls (rather than one call for F2F cases). These checks were always completed over the phone for PB cases. Ideally the first mid-week call would take place on Day 2 of the travel week and the second mid-week call on either Day 4 or 5. The intention of conducting 2 calls was to help ensure that the data quality on the travel records remained as high as possible, by minimising the number of days between the respondent travelling and then having to recall their travel to the interviewer over the phone. Additionally, spreading the mid-week check over 2 calls helped to break the activity down into smaller, more manageable portions.

The proportion of households receiving a mid-week check in 2024 is shown in Table 3.9. Comparable figures for 2023 and 2019 are shown in Tables 3.10 and 3.11. These tables show the figures for each possible outcome:

• a mid-week conducted by phone

• a mid-week check conducted in person

• no mid-week check conducted.

The table is broken down by fully co-operating and partially co-operating households.

In 2024, 77% of fully productive households had a mid-week check (either by phone or in-person), which is very close to 2019 (80%). Of those mid-week checks, 28% were conducted in-person in 2024 compared to 30% in 2019.

Note: figures in the tables below may not total 100% due to rounding.

Table 3.9: Proportion of households where a mid-week check was conducted (either by phone or in-person), by fully and partially co-operating households (2024)

Type of check	Fully co-operating	Partially co-operating	Total
Mid-week check conducted by phone	49%	41%	48%
Mid-week check conducted in-person	28%	18%	27%
No mid-week check	23%	41%	26%
Base (households)	7,530	1,445	8,975

Table 3.10: Proportion of households where a mid-week check was conducted (either by phone or in-person), by fully and partially co-operating households (2023)

Type of check	Fully co-operating	Partially co-operating	Total
Mid-week check conducted by phone	48%	41%	47%
Mid-week check conducted in-person	28%	13%	26%
No mid-week check	23%	46%	27%
Base (households)	6,314	1,279	7,593

Table 3.11: Proportion of households where a mid-week check was conducted (either by phone or in-person), by fully and partially co-operating households (2019)

Type of check	Fully co-operating	Partially co-operating	Total
Mid-week check conducted by phone	50%	33%	48%
Mid-week check conducted in-person	30%	22%	29%
No mid-week check	20%	44%	23%
Base (households)	6,162	663	6,825

The pick-up call

For F2F cases, at the end of the travel week, the interviewer called at the household (generally within a few days) to pick up and check the travel diaries and to carry out another much shorter interview, known as the pick-up interview. The pick-up interview collected information about:

• new vehicles acquired since the placement interview (for the household)

• the disposal of vehicles recorded at the placement interview (for the household)

• new driving licenses acquired since the placement interview (for individuals)

• new season tickets acquired since the placement interview (for individuals)

• mileage details (for each household vehicle)

This pick-up call was also when the diaries were collected and checked before being sent back for coding by NatCen’s Operations Department. The mileage chart was collected also, and the details transferred into the CAPI questionnaire either during the interview or later on by the interviewer at home.

For PB cases, the pick-up interview was conducted over the phone, and he remaining days of the travel record were completed by the interviewer during the same call. The data collected by the mileage chart was collected over the phone at this stage too.

During F2F data collection, the pick-up interview was completed on the laptop using the CAPI questionnaire, or on rare occasions using a paper questionnaire as a fallback option (with the interviewer ensuring that the paper-recorded details were transferred into the CAPI questionnaire afterwards). The paper version of the pick-up questionnaire was introduced in 2002 to enable interviewers do the pick-up interview on the doorstep where respondents were unwilling to let them into the property again. For PB cases, the pick-up interview was always completed using the CAPI questionnaire over the telephone.

Table 3.12 shows the mean length (in minutes) of pick-up interviews for 2024 and all previous survey years going back to 2002, for both fully co-operating households and the total achieved sample of co-operating households. On average, the pick-up call (including the interview and checking the travel diaries) lasted just under 14 minutes for fully productive households in 2024. This call was ideally made within 6 days of the end of the travel week. The 2024 average length of the pick-up call is slightly lower than the last pre-pandemic figure (14.5 in 2019).

The mean length of the pick-up interview reported here is calculated using the amount of time entered by the interviewer into the CAPI program. Although the length of pick-up is also calculated within the CAPI programme, this is not a reliable source because the pick-up interview is sometimes conducted on paper with the interviewer entering the information into the program at home. In previous technical reports, the pick-up length has not been calculated in a consistent manner. The pick-up interview lengths shown in Table 3.12 replace those in earlier NTS technical reports and are based on the interviewer-reported length.

Table 3.12: Mean length (in minutes) of pick-up interview in minutes, by fully co-operating and total co-operating households (from 2024 going back to 2002)

Year	Fully co-operating	Total co-operating
2024	13.9	13.8
2023	14.0	14.0
2022	15.5	15.5
2021	18.1	18.0
2020	17.1	16.9
2019	14.5	14.4
2018	15.1	15.0
2017	14.7	14.6
2016	15.1	15.2
2015	15.5	15.3
2014	15.4	15.3
2013	15.1	15.0
2012	15.9	15.7
2011	16.4	16.3
2010	16.0	15.9
2009	16.4	16.2
2008	16.2	16.0
2007	16.6	16.4
2006	16.3	16.1
2005	18.6	18.5
2004	19.0	18.7
2003	18.6	16.3
2002	18.4	18.0

Gazetteer

The gazetteer is used to code the location of where respondents work and the origin and destination of any long-distance journeys during the CAPI interview. It is also used to code the location of journeys made in the travel record using the Diary Entry System. It holds a list of locations in Great Britain which is based on 1km grid references.

After the location of the respondent’s place of work has been established through the gazetteer, a follow-up question may be asked during the interview to determine more precisely where they work in relation to a common reference point. For respondents working in larger towns and cities they would be asked whether their place of work is within a short walking distance (between 5 and 15 minutes’ walk) from the reference point for their particular town of city, such as a landmark or a main street. Likewise, for respondents working in non-urban areas they would be asked if their place of work is ‘within 5 minutes’ walk of the main shopping or business centre’. The gazetteer maps these reference points against its list of locations, details of which are provided in the lookup table in Appendix J. Respondents working in other urban areas (that is, besides the larger towns and cities for which a reference point is given) would not be asked the follow-up question.

During the interview and the data checking stage, the CAPI and Diary Entry System uses the gazetteer’s grid references to calculate reasonably precise distances between each named location using checks based on straight line distances. For trips of 15 miles or over, respondents’ estimates of distance are flagged for checking if they are not between 0.75 and 1.75 ‘as the crow flies’ miles at the data processing stage. Discrepancies in distance estimates are not flagged where respondent and ‘as the crow flies’ miles are both below 15 miles.

Outcome coding

Interviewers were required to assign an outcome code to every address in their point. The fully and partially co-operating codes (110 to 130 and 241 to 262) were automatically computed for them by the CAPI program, whereas they had to input non-productive codes themselves into the CAPI program (with a small number of codes requiring office approval to be used).

Note: these fieldwork outcome codes are different to the participation categories that are used for the purposes of weighting.

For a household to be classed as fully co-operating, the placement interview had to be fully completed, and wholly filled in travel diaries had to be collected for all household members. The placement interview needed the household section, all individual interviews (whether in person or by proxy), and at least one vehicle section (if applicable) to be completed.

The household was coded as partially co-operating if any of the following applied, namely:

• the household section of the placement questionnaire was not completed

• anyone was coded as ‘not available’ for the individual section

• no vehicle questionnaire sections were complete (if applicable)

• travel diaries were not collected for all household members at pick-up

• any of the travel diaries were incomplete (for example, missing days)

The range of possible fieldwork outcomes is shown below in Table 3.13.

Table 3.13: NTS outcome codes

Code	Type	Outcome
110	Fully co-operating	Fully productive: All desired respondent(s) in person
120	Fully co-operating	Fully productive: Partly by desired respondent(s) in person, partly by proxy
130	Fully co-operating	Fully productive: By proxy
241	Partially co-operating	Partial productive: Desired respondent(s) in person, with some travel records
242	Partially co-operating	Partial productive: Desired respondent(s) in person, with no travel records
251	Partially co-operating	Partial productive: Partly by desired respondent(s) in person, partly by proxy, with some travel records
252	Partially co-operating	Partial productive: Partly by desired respondent(s) in person, partly by proxy), with no travel records
261	Partially co-operating	Partial productive: By proxy, with some travel records
262	Partially co-operating	Partial productive: By proxy, with no travel records
310	Non-contact	No contact with anyone at address
321	Non-contact	Contact made, but not at selected dwelling unit (used only for addresses with multiple dwelling units)
322	Non-contact	Contact made at (selected) household but not with responsible adult
328	Non-contact	Multi-household dwelling units only: contact made at (selected) dwelling unit, but not with anyone from selected household
333	Non-contact	Household opt-in, but telephone number wrong
410	Refusal	Office refusal
421	Refusal	Information refused about number of DUs at address
428	Refusal	Contact made but information refused about number of households
431	Refusal	Refusal before interview
432	Refusal	Proxy refusal
433	Refusal	Refusal of face-to-face interview due to COVID-19, no agreement for remote interview
440	Refusal	Refusal during interview
450	Refusal	Broken appointment, no recontact
510	Other unproductive	Ill at home during survey period
520	Other unproductive	Away or in hospital during survey period
530	Other unproductive	Physically or mentally unable/incapable
540	Other unproductive	Language difficulties
550	Other unproductive	OFFICE APPROVAL ONLY: Lost productive
561	Other unproductive	Household member ill with COVID-19 or related symptoms
563	Other unproductive	Household member is shielding from COVID-19
565	Other unproductive	Household has been instructed to self-isolate
591	Other unproductive	Interview completed but respondent requested deletion
599	Other unproductive	OFFICE APPROVAL ONLY: Other unproductive
612	Unknown eligibility: no contact made	OFFICE APPROVAL ONLY: Issued, but not attempted
614	Unknown eligibility: no contact made	OFFICE APPROVAL ONLY: Issued, but not attempted due to COVID-19 local lockdowns
620	Unknown eligibility: no contact made	OFFICE APPROVAL ONLY: Inaccessible
621	Unknown eligibility: no contact made	OFFICE APPROVAL ONLY: Inaccessible due to COVID-19
630	Unknown eligibility: no contact made	OFFICE APPROVAL ONLY: Unable to locate address
640	Unknown eligibility: no contact made	Unknown whether address contains residential, no contact made after 6 or more calls
650	Unknown eligibility: no contact made	Residential address, unknown if occupied due to no contact made after 6 or more calls
690	Unknown eligibility: no contact made	Other unknown eligibility (no contact made)
710	Ineligible or deadwood	Not yet built or under construction
720	Ineligible or deadwood	Demolished or derelict
730	Ineligible or deadwood	Vacant or empty
740	Ineligible or deadwood	Non-residential address (for example: business, school, office, factory, etc.)
750	Ineligible or deadwood	Address occupied, but no resident household (for example: holiday or weekend home)
760	Ineligible or deadwood	Communal establishment or institution, no private dwellings
770	Ineligible or deadwood	Residential, but not eligible for survey (for example, no-1 aged 16 and over)
780	Ineligible or deadwood	OFFICE USE ONLY: Address out of sample
790	Ineligible or deadwood	Other ineligible
810	Unknown eligibility: contact made	Information refused about whether address is residential
820	Unknown eligibility: contact made	Contact made, but not with someone who can confirm the presence of a residential household
830	Unknown eligibility: contact made	Information refused about whether resident(s) are eligible
850	Unknown eligibility: contact made	Unable to confirm eligibility due to language difficulties
890	Unknown eligibility: contact made	Other unknown eligibility (contact made)

For 2021, in response to the COVID-19 pandemic, some new outcomes were added to the survey (as shown in Table 3.13 above) including in 2024, namely:

• 433, refusal of face-to-face interview due to COVID-19, no agreement for remote interview

• 561, household member ill with COVID-19 or related symptoms

• 563, household member shielding from COVID-19

• 565, household has been instructed to self-isolate

• 614, OFFICE APPROVAL ONLY: Issued but not attempted due to Covid-19 local lockdowns

• 621, OFFICE APPROVAL ONLY: Inaccessible due to COVID-19

Addresses which were not issued to an interviewer or which were issued but not coded out (and therefore deemed to be unworked) were defaulted to the outcome code of 612 at the end of fieldwork for the quota month.

The shopping voucher incentive, conditional incentive experiment and thank you letter

Each member of the fully responding household was given a £5 shopping voucher (in the form of a physical gift card) by interviewers at the end of the pick-up call. Interviewers explained to respondents that the gift card would be activated by the office within 2 to 3 working days. For PB cases, the same £5 incentive was used, but this was sent out by NatCen’s Operations Department due to the fact that the pick-up call would have been conducted over the phone.

During the second quarter of 2024, an experiment was conducted to explore the efficacy of increasing the value of the conditional incentive. The performance of 2 conditional incentive values were tested:

• the traditional £5 shopping voucher, offered to each household member if all members fully complete the study.

• a £10 shopping voucher, offered under the same conditions.

Table 3.14 displays the proportion of fully productive households and then the proportion of partially productive households for each incentive condition, along with the results of statistical testing, namely for the chi-squared test measure (‘Χ²’) and statistical significance (‘p’) used throughout this report. The figures are presented for each of the 3 months individually and then for the quarter as a whole.

Table 3.14: Proportion of fully productive and partially productive households by incentive condition

Case Type	Period	£5 incentive	£10 incentive	Χ2	p
Fully productive	April	31.1%	32.9%	0.693	0.405
Fully productive	May	35.1%	37.3%	0.951	0.329
Fully productive	June	34.2%	34.3%	0.000	1.000
Fully productive	Quarter 2	33.4%	34.8%	1.200	0.273
Partially productive	April	8.3%	4.0%	15.242	less than 0.001
Partially productive	May	6.1%	6.0%	0.002	0.961
Partially productive	June	7.1%	6.1%	0.554	0.457
Partially productive	Quarter 2	7.2%	5.4%	7.987	0.005

For fully productive cases, over the 3-month period, the £10 incentive group achieved a 1.4 percentage point higher response rate overall compared to the £5 group, however this difference did not reach statistical significance. In both April and May, the £10 incentive group outperformed the £5 group by approximately 2 percentage points. In June, response rates were almost identical, however none of these differences were statistically significant.

Partially productive cases, where not all household members completed the diary, were more common in the £5 condition than in the £10 condition. This difference was primarily driven by the results in April, where the proportion of partially productive cases was twice as high in the lower incentive group.

Due to the lack of evidence of an improvement in response rates when increasing the conditional incentive from £5 to £10, the decision was made to retain the £5 shopping voucher on the NTS for the 2025 survey year. The findings are detailed in the National Travel Survey: conditional incentive experiment report.

Starting in 2019, interviewers also handed out a thank you letter at the end of the pick-up call (see Appendix I). The thank you letter was addressed from the DfT and given as a recognition of the respondents’ time and effort. For PB cases, an equivalent letter was mailed out by the Operations Department along with the gift card(s).

Response rates

Tables 3.15 to 3.18 show the response rates in 2024 for England as a whole (the national response rate), the response for Inner London and Outer London, and finally the response for the rest of England excluding London. These tables show the response rate for the Achieved Sample, which includes all sampled addresses, and also the Standard Response Rate, which includes eligible households only and is the measure by which response is monitored year on year.

The overall national Standard Response Rate in 2024 was 32%, but this was lower in Inner London (20%), and very slightly lower in Outer London (31%). The response rate for the rest of England (excluding London) was 33%.

Table 3.15: NTS National (England) response rates

Category	Achieved Sample	Achieved Sample Response Rate	Standard Response Rate
Set sample	25,608	100%	not applicable
Ineligible or deadwood	1,912	7%	not applicable
Unknown eligibility	2,294	9%	not applicable
Eligible households	23,508	92%	100%
Fully co-operating	7,530	29%	32%
Partially co-operating	1,445	6%	6%
Refusal to co-operate and other unproductive	10,003	39%	50%
Non-contact	2,424	9%	12%

Table 3.16: NTS Inner London response rates

Category	Achieved Sample	Achieved Sample Response Rate	Standard Response Rate
Set sample	1,804	100%	not applicable
Ineligible or deadwood	137	8%	not applicable
Unknown eligibility	190	11%	not applicable
Eligible households	1,651	92%	100%
Fully co-operating	336	19%	20%
Partially co-operating	112	6%	7%
Refusal to co-operate and other unproductive	729	40%	52%
Non-contact	300	17%	21%

Table 3.17: NTS Outer London response rates

Category	Achieved Sample	Achieved Sample Response Rate	Standard Response Rate
Set sample	2,486	100%	not applicable
Ineligible or deadwood	243	10%	not applicable
Unknown eligibility	150	6%	not applicable
Eligible households	2,227	90%	100%
Fully co-operating	689	28%	31%
Partially co-operating	113	5%	5%
Refusal to co-operate and other unproductive	1,032	42%	51%
Non-contact	259	10%	13%

Table 3.18: NTS England excluding London response rates

Category	Achieved Sample	Achieved Sample Response Rate	Standard Response Rate
Set sample	21,318	100%	not applicable
Ineligible or deadwood	1,532	7%	not applicable
Unknown eligibility	1,954	9%	not applicable
Eligible households	19,631	92%	100%
Fully co-operating	6,505	31%	33%
Partially co-operating	1,220	6%	6%
Refusal to co-operate and other unproductive	8,242	39%	49%
Non-contact	1,865	9%	11%

As mentioned in section 2.4 the NTS oversamples Inner and Outer London with the aim of achieving responding sample sizes that reflect the regional distribution without the need for corrective weighting. The degree of oversampling in 2024 was based on estimates of differences in response rates between Inner London, Outer London and the rest of England.

From 2006 onwards, weights were introduced in order to correct for non-response (see Chapter 5 for a detailed description of the weighting). Data back to 1995 have been weighted retrospectively.

Back-checking and quality control

Like all NatCen projects in the field, the NTS was back-checked to ensure that interviewers were working to the standards to which they were trained and in accordance with the specific project requirements on which they were briefed.

A minimum of 10% of the total productive interviews were back-checked, the majority (usually 90%) by telephone, but where this was not possible (usually 10%) by letter. If the responses received indicated significant deviations from the standards set, a supervisor was asked to personally revisit the address(es) concerned. Back-checking was carried out usually within 2 weeks, and always within 4 weeks, of the interview date. The back-checking exercise did not find any systematic errors in the way interviewers were working for 2024.