1) They are driving a car that they are not used to. Usually
people start their driving hoilday right away on their rental car,
did not get enough time to be familiar with it first.
2) Poor planning - people do not calculate the time they need
correctly. They just blindly measure the distance. They did not
consider the type of road, and take into consideration that they
stop a lot to take photo and explore things. Thus they under
estimate the time they needed. Also must take note of the day light
time, for some countries at certain season - sunset start to set by
4 or 5 p.m
3) Do homework on road to take. Some road in area like grampians
are not really mean for normal travelling. There are some special
road that are for slow nature observation.
4) Some road oversea - can be very straight and have field on
both side, esp when it is between 10+ to 3+ with the heat and the
light - can lead to driver to be lost concentration
and doze off.
5) Crosswind - usually you can feel it, if you driving on
straight road easily. Usually it is curve or turning - which
crosswind cause accident .
6) Wild animals - kangroos & emu at grampian. Usually they
start coming out in sunset. Outback - even have horses and
camels.
One advice is alway put a few days to stay in the city at the
end to to use a buffer - so you do not need to rush, the most eat
into those days.
This way you do not have the need to rush, in victoria - there
is place to stay all along the way . that is what is call driving
hoilday - drive to where sleep at where and carry on.