# Where we look when we steer

My intuition gives me an explanation of this. Assume for the moment
that it really is true: when driving, we focus on the tangent point of
the left side of the road. Also assume that the road is a series of
distinct segments, each with a constant curvature over that segment.

Now I believe that, while the car is driving within one segment, if
the perception of the tangent point of some road-parallel curve (left
or right edge would do) is not kept fixed in the center of the
body-relative visual field (head and eyes both kept fixed), then it
would necessarily be the case that the car's curvature would not match
the road's over that segment. Therefore by controlling for a fixed
tangent point, staying on the road is achieved.

When transition is made to a new segment, the tangent will wander in
the field. By adjusting the wheel, to a new curvature, control can
then be re-achieved. By constant adjustment, control can be achieved
over a continuously changing curvature road (infinitesimal length
segments).

O----------------------------------------------------------------------------->

Dr. Cliff Joslyn, Cybernetician at Large, NRC Research Associate
327 Spring St #2, Portland, ME, 04102, USA
Systems Science, SUNY Binghamton NASA Goddard Space Flight Center
cjoslyn@bingsuns.cc.binghamton.edu joslyn@kong.gsfc.nasa.gov

V All the world is biscuit shaped. . .

When I saw the announcement of the article (which was nice to see it
here) I got it and was a bit disappointed too. It might well be that
we use the tangent point as a cue for steering, but that can't be all!
The first question which came to my mind was: where do you look when
there is not road? i.e. features in the 'objective' environment.

Motorcyclists where possible often look at the exit of the curve, where
it straightens up again. They have more perceptual problems than car
drivers to contend with, since the bike banks over as well as turning,
and have has to decide whether to orient their vision with respect to
the visual horizon or the local acceleration-produced "down". Runners
both animal and human have the same problem, of course; it's cars which
behave oddly when cornering, and only their ubiquity in our century
sanctions their behavioural oddity. Interestingly enough, the answer to
the gaze-orienting question correlates with being political left or
right. Anyone care to guess which way and suggest a reason?

But your question can't be answered by an experiment conducted on the
run round Arthur's Seat in Edinburgh (the site of the Nature
experiment), since every single corner is seriously blind. A popular
way of scaring strangers to the city is to take them on a sight-seeing
spin round this twisty little road. When they goggle mute and
ashen-faced at you at the end you say casually to them: "Oh, didn't you
realise it's a one way system? Gosh, I am sorry, you must have been
terrified!"

Chris Malcolm