The same three researchers conducted all of the trials,
two laid out the course and collected the simulated roadkill
and the third (WC) observed the roadkill. In order to
establish whether there was a difference in detection rate
with the same observer as the driver or as the passenger
(Clevenger et al. 2003; Barrientos and Bolonio 2009), the
full set of transects was repeated with “driver-as-the-observer”
and “passenger-as-the-observer.” In these cases, the
observer was the principal researcher and was considered
an experienced observer.