P Samuel has rightly raised issues about the latest research into DRL's. Of
course on the other side newer vehicles do more kilometres, are more likely
to be in peak hour traffic where multiple vehicle crashes are common et
cetera. However Michael Paine was after information on the latest studies
and that report was in response to his request. And I trust Michael to
analyse all reports professionally.

The principle issue is whether DRL's will make it more likely the
subconscious will associate what it "sees" with a vehicle risk. Studies done
show that in crashes "failing to see the other party is very common with
figures of 60% or more quoted for drivers not seeing motorcycles, drivers
not seeing pedestrians, pedestrians not seeing vehicles, drivers not seeing
trucks and so on.

I suspect that PSamuel might be one of those who put this high level of
saying they didn't see down to "not wanting to take responsibility". But the
reality is that once you put the major part of the visual processing in
driving into the subconscious (which is what happens by the time we become
experienced drivers - Wendy McDonald's research in 1980's showing novice
drivers could recall much more of the road environment and signs than
experienced drivers clearly demonstrated this) there is a risk that the
subconscious will make a "mistake". The optical system and brain work
together to identify objects that are risks to the driver. in doing this it
has to differentiate for instance between big rectangular objects that are
no risk (houses) and big rectangular objects that are a risk (large trucks).
And some moving objects are common and a great risk (light vehicles) and
others are rare and little risk to the driver (motorcycles). So there is the
tendency than for the brain to ignore motorcycles. And of course the same
visual processing goes on when we are walking.

So the potential for DRL's is that in daytime conditions the subconscious
will associate white lights with vehicles that may be a threat and so alert
the conscious mind to that threat. Hence there is potential for lower
multiple vehicle crashes (greater chance that either or both drivers will
subconsciously see the oncoming risk by associating white lights in daylight
with that risk), lower pedestrian crashes (but only from the pedestrian
side - the driver still will not "see" the pedestrian) and even lower
motorcycle crashes (because white light associated with light vehicles are a
threat so daytime white lights on motorcycles more likely to be seen as a
threat).

So for PSamuel's and Bob Murphy's information, DRL's do have the potential
to reduce crashes in daytime. the trick is to work out how that can be done
technically in a way that minimises capital and operating costs.