@article{ref1,
title="Visibility of traffic control devices: catering for the real observer",
journal="Ergonomics",
year="1976",
author="Johnston, A. W. and Cole, Barry L. and Jacobs, R. J. and Gibson, A. J.",
volume="19",
number="5",
pages="591-609",
abstract="Abstract unavailable.",
language="",
issn="0014-0139",
doi="",
url="http://dx.doi.org/"
}