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Comparison of travel time using the Time Use Survey and National Travel Survey

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Trip details: TIME, method of travel, purpose etc ... Only national source on time spent travelling - apart from TUS. What do DfT want from TUS? ... – PowerPoint PPT presentation

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Title: Comparison of travel time using the Time Use Survey and National Travel Survey


1
Comparison of travel timeusing the Time Use
Survey and National Travel Survey
  • Time Use Seminar 22 June 2004
  • Dorothy Salathiel Department for Transport

2
What is the National Travel Survey?
  • Long running household survey of personal travel
  • Very detailed information on households,
    individuals and vehicles through personal
    interview
  • All individuals keep 7 day diary recording
    details of trips
  • Trip details TIME, method of travel, purpose etc
  • Only national source linking personal
    characteristics to trips
  • Only national source on time spent travelling -
    apart from TUS

3
What do DfT want from TUS?
  • Better estimates of time spent travelling
  • recording of short travel episodes
  • walking
  • coverage of travel excluded from NTS
  • context in relation to other activities
  • test value of time use diary compared with travel
    diary

4
Can differences between the surveys be explained
and questions answered?
5
Time recording in TUS and NTS
  • Similarities
  • household interview
  • time recorded in a diary by respondent
  • GB
  • compare for over 16s
  • trip is one way course of travel
  • Differences
  • TUS in 10 minute blocks and NTS to nearest minute
  • TUS 2 days NTS 7 days
  • NTS short walks only on Day 7
  • Minor differences in trips included
  • Inclusion of travel as secondary activity
  • NTS not weighted but profiles similar

6
Day 7 issue
  • Short walks only included in NTS on Day 7
  • Therefore comparison uses just Day 7 data
  • Number of trips recorded declines through the
    week (fatigue) so Day 7 underestimates compared
    with Days 1-6
  • People have not recorded short walks on Days 1-6,
    so may forget to do so on Day 7
  • Intend to gross up Day 7 for TUS comparison using
    Day 1 but not done yet

7
Large difference in total travel time recorded,
across all modes
8
NTS has more people with no trips in a dayTUS
has more people doing at least 90 mins travel a
day
Adults GB
9
Total travel time number of trips per day x
time per trip
10
NTS has more days with no tripsTUS records more
days with 1,3 5 etc trips
Adult GB
11
Characteristics of people doing no trips
  • More likely to be
  • female
  • looking after home
  • sick
  • unemployed

12
Where a trip is done, little difference for main
modes. If redistribute unspecified then
differences very small
13
NTS has higher proportion with no car stage. TUS
higher for 1,3 5 etc stages
14
NTS has more days with no walk stages.TUS more
days with 1,3,5 stages
15
Summary of key travel statistics
16
Average travel time per stage (minutes)
17
Modal shares(spreading TUS unspecified evenly
over modes)
18
Recording travel time
  • What should happen
  • NTS should record all walks over 50 yards, ie of
    more than 1 minute
  • TUS should not record travel of 1-4 minutes, ie
    under 1/4 mile
  • What do we think does happen
  • NTS misses short trips
  • NTS often records trips to nearest 5 minutes
  • TUS records trips under 5 minutes because they
    dont want to ignore the activity

19
Stage duration Distributions closer if exclude
NTS trips of 1-4 mins
20
Walks travel time per stage (excluding NTS 1-4
mins and half 5 mins)
NTS stage duration increases from 15 to 20 mins
compared with TUS 19 mins
21
Car travel time per stage (excluding NTS trips
of 1-4 mins and half 5 mins)
NTS increases from 20 to 21 mins compared with
TUS of 28 mins
22
Summary
  • TUS records about 40 more total travel time per
    day than NTS
  • TUS records about 5 more trips/stages per day
  • NTS records more non travel days
  • TUS records about 30 more travel time per
    trip/stage
  • Most of this is due to more long car trips in TUS

23
Conclusion from comparison between Belgian time
use and travel surveys
  • transport survey underestimates numbers of trips
    and time spent
  • TUS biases time spent because it rounds durations
    of very short trips upwards
  • Surveys more consistent for daily number of trips
    and modal shares
  • very similar to GB result!

24
Conclusions
  • The uncertainty over how short time periods are
    recorded makes it difficult to compare results
  • We need to do more work to reduce differences eg
    grossing up day 7
  • Differences mean we cannot answer our questions
    eg better information about short travel
    episodes and walking
  • But there are lessons for the NTS, eg record
    short walks on Day 1?
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