Country Driving-Open road and highway driving.
Highway driving requires all the skills of driving in city and suburban traffic,
but there are many other points the driver must consider as well. Town driving,
customarily up to 60 km/h, is very different from driving at 100 km/h or faster.
City dwellers who rarely venture into the country should proceed on the open road
with caution until they become accustomed to unfamiliar conditions.
Highway cruising introduces a number of physical forces not normally experienced
in restricted speed zones. Some of these are:
Stopping Distances
A vehicle travelling at 100 km/h will require four times the stopping distance
of one moving at 50 km/h. From 150 km/h, the stopping distance will be nine times
that from 50 km/h. (In mathematical terms, stopping distance increases as the square
of the speed). Here is another case where knowledge, experience and anticipation
are so vital.
Vehicle Stability, sudden braking may introduce difficulties, and the inexperienced
driver must adjust touring speed so as to have the vehicle under complete control
in the event of any emergency.
Judgment of Speed
Drivers - and passengers -on entering a restricted speed zone after open-road
cruising have been heard to remark that a speed of 60 km/h seems to be almost walking
pace. It is well known that the human system takes time to adjust from fast to slower
motion. Drivers must realise that the converse also applies, and that a sudden change
of speed from, say, 60 to 100 km/h will require both physical and mental adjustment.
This may account for the fact that many accidents occur shortly after the beginning
of a journey. Any substantial increase in speed should therefore be gradual, the
driver building up to the higher speed rather than accelerating hastily at the first
opportunity.
The Use of Speed
Blanket or absolute speed limits have been laid down in this country and many others.
To an experienced driver on freeway or highway conditions these limits may seem
unduly slow. However, in this text, the discussion automatically associates speed
with prevailing conditions. Car manufacturers are giving more and more attention
each year to power and speed, which continue to be used as strong selling points
for their products.
What has been said and written about speed, does not always take into account that
is entirely relative to circumstances including the mechanical condition of the
vehicle and the capability of the driver. No sane person will want to drive excessively
fast in heavy traffic, where there is danger to pedestrians, or where road or weather
conditions are at all doubtful. Above all, speed and power should never be used
competitively on public roads in ordinary traffic. To do so is immature and often
dangerous.
The ability of a driver to drive fast with safety depends entirely on skill, knowledge
of the characteristics of the vehicle, and on prevailing conditions. Stability,
cornering and braking capacity of the vehicle under various conditions are of tremendous
importance; and it is a foolish, inconsiderate driver who drives fast without first
learning to control the car at lower speeds. Faster speeds allow less margin for
error and bring far more serious consequences in the event of a mishap.
Modern cars with very quiet, smooth engines and transmissions can be deceptive and
speed may creep up without the driver being aware of it. The natural forces affecting
stability, cornering, braking, etc., are just as much present as in more noisy vehicles
where the mechanical parts are felt to be working really hard, perhaps with accompanying
vibration. Very often, too, softly sprung vehicles, which feel so pleasant, are
less stable on cornering than their more rigidly sprung counterparts. This may be
because of body roll caused by centrifugal force, and the softer the suspension
the more the roll. Under extreme conditions the body of a vehicle may lean outwards
to the extent that the inside wheels lose adhesion, partially or even totally. Such
driving is very dangerous; clearly the driver at this stage, is travelling much
too fast, and has either ignored, or through lack of experience, failed to recognise
the danger signs.
Above all else, fast driving requires total concentration, and the driver should
remember that sustained driving at high speeds is tiring, because of the mental
effort required. With this knowledge, it is easy to recognise the need to be in
reasonable physical condition, and to understand the value of an occasional spell
from the wheel. Beware the driver who claims to be able to drive all day without
ever becoming tired.
Reading the road surface
The type and condition of the road surface affect the stability of a vehicle very
greatly. An alert driver will note any deterioration, eg. change from bitumen to
loose gravel, and will know that the cornering and braking capacity of the vehicle
is sharply reduced. Faulty cross fall of the surface on curves is a common trap
for the unwary.
All highways and most roads are designed with cross fall for drainage purposes.
In urban and suburban roads, the pavement is normally cambered or sloped down from
the centre line to gutters or drains on each side. On rural roads and highways where
speeds are considerably higher, similar camber is provided on straight sections,
but on curves, particularly those with small radii, the cross fall may all be in
one direction, i.e. down towards the inside of the curve.
This one-way cross-fall, known as super elevation, is designed to counter part of
the cornering or centrifugal force generated in a fast moving vehicle, the grip
of the tires absorbing the remainder.
Since centrifugal force increases as the square of the speed (eg. twice the speed
generates four times the centrifugal force), if a corner is taken faster than the
designed speed, the vehicle will tend to run wide, particularly if the road surface
is wet or in bad condition.
Thus a highly important part of driving is studying the shape and condition of the
road surface ahead and being ready to reduce speed quickly and smoothly when necessary.
Read the road as far ahead as possible, and always note any warning signs which
are displayed on the roadside.
The sight of traffic bunching will be familiar to anyone doing much country touring,
especially on our secondary roads with a single lane in each direction; and this
is aggravated by open road speed zoning. On seeing one vehicle emerge from round
a corner or over a crest, expect that a number of vehicles might be following closely
behind. This is usually caused by a slow-moving vehicle at the head of the queue.
In emergencies, the sides of the road may be of value. Stable road shoulders might,
for example, provide an escape route from a head-on collision where a driver coming
from the opposite direction is on the wrong side of the road, or out of control.
At times a driver may be forced to steer the vehicle partly on to the shoulder of
the road - or he may do so inadvertently. That is to say, the nearside wheels may
be running on unstable ground while the offside wheels remain on the pavement. If
the shoulder or verge is soft or slippery and much below the surface of the pavement,
as is often the case, difficulty in steering may be experienced.
A shoulder of loose metal or gravel requires particular care. In sudden acceleration
or braking, the grip of the nearside wheels will be far less than those on the offside.
The vehicle may skid and slew out of control. Trying to force the vehicle back onto
the road, especially if the shoulder is lower than the pavement, can also be dangerous.
The sharp edge of the pavement will initially have a tram-line effect, and will
prevent the near side wheels from returning to the pavement. The extra steering
effort to overcome this may take the vehicle some distance across the road before
the driver can regain a proper course. The best procedure is to maintain direction
initially, avoiding braking or acceleration, but allowing the vehicle to slow down
by itself. To steer back fully on to the pavement, choose a spot where road shoulder
and pavement are level, or nearly so, and be sure that no other vehicle is coming
from either direction.
Unsealed roads
Nearly all our main arteries and many secondary roads particularly those near cities
and big towns, are bitumen surfaced. Nevertheless there are many kilometres of unsealed
roads, varying from wide, well-aligned and graded gravelled roads to bush tracks.
Many city dwellers have seldom or never driven on unsealed surfaces, and some are
apprehensive at the prospect.
There are certain inherent disadvantages in sealed roads, even those of higher standard,
for example:
(1) The grip of the tires is substantially reduced.
(2) There are no road markings such as centre lines, edge-line etc.
(3) It is often difficult to distinguish between the edge of the gravelled pavement,
and the unpaved, and possibly soft shoulders.
(4) In dry weather there may be considerable dust from the vehicle(s) ahead.
(5) Stones may be thrown up from the surface by approaching or overtaking vehicles
as well as a vehicle you might be following. Beware when following a vehicle with
dual wheels; quite a large stone may easily be lodged between the two tires and
then suddenly released.
(6) The surface is unlikely to be consistent; there may be scattered potholes, corrugation
etc.
(7) There is always a deterioration of the surface during or after rain: this is
usually in the form of potholes, rills and wash-outs. Poorer pavements may become
muddy and be extremely slippery or even impassable.
Driven on properly, loose surfaces need not present a hazard but they do require
added care and alertness. Always reduce speed as the surface changes from bitumen
to gravel and try to get the "feeling" of the new surface. Unless you are experienced
on loose-surface driving, particularly in the areas of sudden braking, skid avoidance
and sudden changes of direction, keep speeds down. Experience in off-road skidding
as described will be found invaluable.
Always slow down for potholes, rock outcrops and ruts (common results of wet weather);
taken fast they can damage or even break a suspension as well as throwing your vehicle
completely out of line or even off the road.
Above all, always keep well to the left when travelling round blind corners; an
oncoming driver may be having difficulty in steering his vehicle accurately in such
conditions.
Hazardous periods
Dusk and sunrise bring added visibility hazards. While natural light is insufficient
for picking out details, the headlights are not really effective. Stock and wildlife
tend to be most active at dawn or dusk, when they come out to feed. For the weary
driver who has already covered hundreds of kilometres these are ideal times for
a spell from the wheel, a meal break, or to refuel.
Variation in routine helps the driver to keep alert, and reach the end of the journey
without incident.