Evaluating the feasibility of measuring travel to school using a wearable camera.
BACKGROUND
The school journey is often studied in relation to health outcomes in children and adolescents. Self-report is the most common measurement tool.


OBJECTIVE
To investigate the error on self-reported journey duration in adolescents, using a wearable digital camera (Microsoft SenseCam).


METHODS
During March-May 2011, participants (n=17; aged 13-15 years) from four schools wore wearable cameras to and from school for 1 week. The device automatically records time-stamped, first-person point-of-view images, without any action from the wearer. Participants also completed a researcher-administered self-report travel survey over the same period. Analysis took place in November 2011. Within- and between-subjects correlation coefficients and Bland-Altman 95% limits of agreement were derived, accounting for the multiple observations per individual.


RESULTS
Self-report data were collected for 150 journey stages and SenseCam data for 135 (90%) of these. The within-subjects correlation coefficient for journey duration was 0.89 (95% CI=0.84, 0.93). The between-subjects correlation coefficient was 0.92 (95% CI=0.79, 0.97). The mean difference (bias) between methods at the whole sample level was small (10 seconds per journey, 95% CI= -33, 53). The wide limits of agreement (± 501 seconds, 95% CI= -491, 511) reveal large random error.


CONCLUSIONS
Compared to direct observation from images, self-reported journey duration is accurate at the mean group level but imprecise at the level of the individual participant.
British Heart Foundation Health Promotion Research Group, University of Oxford, United Kingdom. paul.kelly@dph.ox.ac.uk
Paul
P
Kelly
Aiden R
AR
Doherty
Alex
A
Hamilton
Anne
A
Matthews
Alan M
AM
Batterham
Michael
M
Nelson
Charlie
C
Foster
Gill
G
Cowburn
D000293:Adolescent; D001336:Automobiles; D001642:Bicycling / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D010781:Photography / Q000379:methods*; D012574:Schools; D057566:Self Report / Q000592:standards*; D013334:Students; D013997:Time Factors; D014186:Transportation / Q000379:methods / Q000706:statistics & numerical data*; D016138:Walking / Q000502:physiology