British Medical Journal 1994;309:1741-1745 (24 December)

British Medical Journal (December 24, 1994) ;309:1741-1745

Hobby horses
De inertia urbanorum
Ronald Williams, general practitioner
London SW1X 9SW

When I first started using a bicycle for my home visits in central
London 22 years ago I had in mind only fine sunny days. But I saved
even more time when it was wet, for the cars then clogged the streets
in even greater numbers. Now, 87000 cycling km (54000 miles) later,
the disparity between the slowness of the motor car and the swiftness
of the bicycle is so apparent that some comparison of these
vehicles--and their effects--is called for.

In the first century BC Cicero knew the difference between inertia and
velocitas. But he can hardly have imagined, or been equipped to

analyse, the complexities of the machines and mechanisms now in
question, even though the remarkably quiet and highly developed power
unit of the modern bicycle is identical in all important respects to
that used by the ancient Romans in getting themselves on foot to the

Furthermore, the efficiency of the car engine in converting chemical
energy into mechanical work is only 20%1 whereas that of the cyclist
is about 25%.2 This is hardly surprising, for our fuelling, motor, and
control systems have been refined and tested, often to destruction,
under appallingly rigorous conditions over 500 million years.
Fortunately, we can still use this clean and extremely complex
equipment to advantage even in 20th century London, although not while

we remain strapped in our cars. It is a source of continuing wonder to
me that healthy general practitioners will sit inert behind their
steering wheels, queuing for half an hour to cross a bridge, when they
could reach their destination in a fraction of the time on a bicycle.
It is not as if all that much effort were required, for the cyclist
uses five times less oxygen and energy--than the walker in covering a
given distance,3 and 60 times less than the car, assuming average,
moderate speed.4

Our technology now allows us to tap the energy reserves of the earth
to a degree which would have been unthinkable 200 years ago. The known
reserves of oil have risen by 10 times between 1950 and 1990,5 and
reserves of coal and natural gas have risen equally remarkably. Our

use of these resources is rising at a global rate of 2% a year,5 and
estimates of how long the supply will last vary from 100 to 600 years.
World total energy consumption is increasing even faster than the
continuing exponential growth in population--from 1 terawatt (1 x 1012
watts) in 1890 to 3.3 in 1950 and 13.7 terawatts in 1990.6 By 1991 the
world's commercial energy consumption had risen to around 8000 million
tonnes of oil equivalent energy (10.7 terawatts) a year.5 Ninety five
per cent of this energy is derived from fossil fuels and fuel for
transport now accounts for 60% of total oil consumption.5

These advances have made possible, at least in developed countries and
particularly in cities, a level of physical inertia for which we may
not yet be physiologically adapted. Some town dwellers, no doubt
sensing this danger, try to raise their activity level by frequenting
golf courses, where they can be seen ambling gently about or simply
just standing. But for the real inertia enthusiast--if this is not too
much a contradiction in terms--no one spoke out more honestly than
that splendid, if slightly overweight American, Robert Benchley:
"Whenever I feel the need for exercise, I go and lie down for half an
hour until the feeling passes."

A recent advertisement seen above a traffic jam in London announced a
new British car which can accelerate from 0-60 mph (0-96.5 km an hour)
in 6.2 seconds. Now I have the highest regard for this particular make
because I have a much cheaper and less sporty model myself and am
devoted to it, but the energy implications of such acceleration are
worth noting. In my own car it takes me not 6.2 but 22 seconds to
reach that speed, and applying Newton's second law of motion, f = ma
(force = mass x acceleration), the energy--and therefore the
fuel--required for these two acceleration rates differs by a factor of
3 1/2, although the time saved by such acceleration in relation to a
completed journey-- assuming that speed limits are respected--is
small. It would be so nice if exhaust gases did not matter.
Unfortunately, it seems that they do.

In 1990 carbon dioxide emissions into the atmosphere in Britain
totalled 160 million tonnes of carbon. 7 Of this, over 70% came from
power stations, industry and agriculture, and households, in that
order. Road transport accounted for 19%--30 million tonnes of
carbon--and just over half of this derived from the private use of
cars. As this country's contribution to the total world output of
carbon dioxide is barely 3%,7 the global tonnage is quite considerable
and carbon dioxide accounts for roughly half the climate changing
impact of the greenhouse gases. 8

The cyclist's output of carbon dioxide is from 1/60 to 1/100 that of
his or her car,4 and the cyclist breathes out no oxides of sulphur or
nitrogen and no burned or unburned hydrocarbons. Cyclists have the
added advantage that they can calculate the moments of inertia of
their speeding front and rear wheels with a clear head. Ask London
motorists about their cars' moments of inertia and all they can think
of is their local main road or the M25.

Unprecedented levels

According to a recent discussion document from the Department of the
Environment, "the concentrations of greenhouse gases in the atmosphere
are now approaching levels unprecedented for at least the last 100000
years." 7 The particular greenhouse gases implicated are not specified
and no reference is given for this statement, but as it comes in a
government publication it must be true; and indeed it is, although not
scientifically precise, for the methane and carbon dioxide
concentrations 100000 years ago were only average. 9 It was 30000 years
before that, at a time of high temperatures, that these two gases
reached the peak which brought them nearer to present day levels.

Such seemingly esoteric information derives from the analysis of air
bubbles entrapped at various depths in the ice below Vostock, the
Russian research station in central east Antarctica and one of the
coldest places on earth. This decidedly frigid billet is at an
altitude of 3490 metres (11450 ft), has an annual mean temperature of
-55C, is at latitude 78 28'S and rests on an ice sheet 3700 metres
(12100 ft) thick. 9 It is not at all a comfortable surface for the
cyclist, and were it not for the motor car and the Department of the
Environment's anxiety about pollution we would not be considering such
an inhospitable place here.

But for the record, at a depth of 2000 metres (6560 ft) the Vostok ice
cores and their contained air bubbles are believed to date back 150000
years, and this assumption tallies well with climatic information
deduced from deep sea sediment studies.9 By early 1993 the drill had
reached 2546 metres (8350 ft), which takes the measurements well back
into the penultimate ice age.

Yet the Department of the Environment's statement needs putting in
context, and the first thing to be said about the greenhouse or
glasshouse effect is that it is not entirely a bad thing. Without it
our atmosphere would be 30C colder than it now is and life as we know
it would not exist. 10 But what about 130 000 years ago and what about
our ancestors, for surely they deserve a thought? The hominids around
then in this part of the world were Neanderthals, who had evolved in
Europe some 20 000 years earlier and were not to disappear for another
90 000 years, when they were displaced by Homo sapiens sapiens,
Cromagnon man, who almost certainly originated in Africa. By that time
the last ice age was well established; it did not end until about 9000

We can say two things with reasonable certainty about Neanderthal
people. Firstly, they did not own motor cars and, secondly, if they
gave way to inertia they perished. They were probably also, according
to experts at the Natural History Museum, compassionate beings, for
there is evidence that their injured could live long lives.

But if there were then no internal combustion engines; no domestic,
industrial or power station use of gas, oil, or coal; and no large
scale cutting down and burning of forests, what was pushing up the
green-house gases 1 30 000 years ago? Surely this is a relevant
question, yet the Department of the Environment is carefully silent
about that, and with some reason, for the incredibly complex factors
involved in climatic change are still not fully worked out.

The two main greenhouse gases--if we exclude the most important agent
of all, water vapour--are carbon dioxide and methane, 11 and both have
been around for aeons, although methane was a relatively late arrival,
probably not reaching significant atmospheric proportions until the

Archean era--3.8-2.5 billion years ago--when the first anaerobic
methanogenic bacteria appeared. 12 The appearance of free oxygen
awaited the evolution of photosynthetic bacteria and plants 3.0-2.5
billion years ago, and oxygen was not to arrive in significant
atmospheric concentration until even later: two billion years ago. 13

The atmosphere that resulted from the planetary accretion which formed
the earth 4.6 billion years ago was, it seems, dominated by nitrogen,
carbon dioxide, and, as always, water vapour.12 In greenhouse terms
methane is more potent than carbon dioxide and it also is increasing,
at 2% a year.14 Molecule for molecule it is a 21 times more powerful
trapper of the earth's reflected heat than carbon dioxide, although
chlorofluorocarbons are 12 000 times more powerful in this respect8
and in 1990 were increasing by 5% a year. 14 The fourth significant
greenhouse gas, nitrous oxide, is 150 times more powerful than carbon
dioxide in this sense. 11 It arises in part from the denitrification of
soils stimulated by mineral fertilizers, 14 is possibly also produced

by lightning, and certainly produced by the motor car. The fifth
greenhouse gas is ozone, which is approximately 2000 times as
effective as carbon dioxide in retaining the earth's heat, 11 although
present in far lower atmospheric concentration.

The flatulent hippopotamus

About 130000 years ago, when temperatures were high in the last
interglacial period, it is possible that the surge in methane was
related to the increase in area of peat and wet lands following
glacial retreat, 15 the methane arising--as it does in rice
paddies--from microbial decomposition processes in oxygen deficient,
richly organic soils. It has also to be said that the ruminants and
the odd flatulent hippopotamus would have contributed their not
inconsiderable share. When climatic warming reached its peak 125000
years ago this large and potentially lusty mammal is known to have
frequented the area of Trafalgar Square and even to have trundled as
far north as Leeds. Indeed, it extended even further north and west in
Yorkshire, for in 1838 its bones were found beneath a layer of glacial
clay deep under more recent deposits in Victoria cave above Settle,
together with the remains of rhinoceros, bear, reindeer, and ox, all
regular methane, and carbon dioxide, contributors. 16 The amphibious
hippos would no doubt have kept to their rivers and swamps, but they
had for a neighbour an eager collector of left over bones--and a
natural tenant of that high cave--the hyena.

Over short distances a hippopotamus can move faster than a man can
run, and in my particular part of London it could almost certainly
have splashed around faster than today's rush hour motorist can move,
for a male hippo in the mating season seeing off a rival from the
neighbourhood of Hyde Park Corner would not be constrained, as we are,
by queues at traffic lights.

But in this 20th century it is not so much methane as carbon dioxide
which is our problem. It is estimated that some 150000 commuters enter
central London by private car during the weekday morning peak between
7 am and 10 am, the average length of their journey being 24 km (15
miles). 17 About 738000 people come in by train. The carbon dioxide
emission in vehicular exhaust at 22 km per hour (14 mph)--a fair
average speed for these motorists--is 200 g/km, 18 and this more than
doubles when the car is crawling. So at least 1440 tonnes of carbon
dioxide are pumped into the atmosphere each working day by these
commuters' cars alone. The equivalent figure for nitrogen oxides is
14.4 tonnes and for hydrocarbons 28 tonnes.18 Nitrogen oxide emissions
increase very little at slow speeds, but a car moving at 6.4 km per
hour (4 mph) produces five times as much hydrocarbon, soot, and carbon
monoxide as it does at 48 km per hour (30 mph),18 so cyclists may
perhaps be forgiven if they overtake rather quickly.

It has been calculated that the average car puts out four times its
own weight of carbon dioxide each year, 11 and admittedly the 170000 or
so broad leaved trees in the royal parks will mop up a small
proportion of this, as will the trees in the many other parks,
commons, heaths, and squares of London. But they can do this only in
summer, and only growing trees absorb carbon. Dying ones release it,
and a site must be stocked with trees forever if the carbon initially
sequestered on planting it is to be removed permanently from the
atmosphere. Our terrestrial vegetation is patently not keeping pace,
and atmospheric carbon dioxide continues to rise, as it has done since
1900. 19

Apart from the plant kingdom, the only other "sink" for carbon
dioxide-- the oceans and the rocks--cannot possibly absorb it at the
rate at which it is now being produced, 20 and forest clearance by
burning not only drives up atmospheric carbon dioxide but, more
seriously, reduces the total amount of vegetation available to mop it

Before the industrial revolution the level of carbon dioxide in the
atmosphere was 280 parts per million.21 Perhaps not surprisingly this
was also the highest level reached 130000 years ago during the last
interglacial period9--a nice, clean biological maximum. It is now 360
parts per million and rising,20 an enormous proportional increase in
one component of our environment. The level towards the end of each of
the last two ice ages (150000 and 10000 years ago) was 190 parts per
million.9 Throughout the Vostock ice core record, both carbon dioxide
and methane levels correlated closely with temperature-- the colder,
the lower.

Fuelling the crisis

Recent American work suggests that if we continue to burn up our

fossil fuel reserves until they are exhausted, even if forest
clearance is now halted, peak carbon dioxide concentrations of 1000
parts per million are probable within the next few centuries.20 If the
forests are destroyed this figure doubles to 2000 parts per million.

The potentially devastating consequences of too rapid global warming,
not to mention the air quality at ground level in cities, may force us
to rein back on our use of fossil fuels long before the known reserves
are exhausted. Catalytic converters do nothing to reduce emissions of
carbon dioxide, and they have their own snags and imperfections.

Diesel engines produce significant amounts of sulphur dioxide and
carbon particulates, both of which, like nitrogen dioxide, are known
respiratory hazards, especially it seems to people with asthma. "In
the United States over one quarter of all the chlorofluorocarbons
manufactured for refrigeration are used in vehicle air conditioning
units, from which they eventually leak or are vented out,11 so even
some motor cars are now sharing in the assault on the ozone layer.

Bicycles need no catalytic converter and their riders would spurn the
idea of air conditioning. Atomic power seems to be increasingly
suspect and unsatisfactory for a whole variety of reasons. Our only
basic source of energy and continuing life is, as it has always been,
the sun and the radiation from it is colossal. The solar energy

absorbed by the earth in a month is roughly equivalent to the world's
estimated ultimately recoverable reserves of coal, oil, and gas (2 x
1023J or 4.579 billion tonnes of oil equivalent).22

Silicon based photovoltaic cells now exist with a conversion
efficiency of 15%, and efficiencies of 30% are believed to be
possible.5 Allowing 50% for spacing, even such present day cells
placed on a land area only one fiftieth that of Lake Nasser could--in
the hours of daylight--theoretically equal the electrical output of
all 12 turbines of the Aswan High Dam--2.1 milion kilowatts. And the
current energy demand of the whole world could be met if only 0.1% of
the earth's total surface--land and sea--were used as a collector to
convert incident solar energy at 10% efficiency.22 There is, after
all, space and to spare. A twentieth of the earth's land surface can
be classified as extremely arid,23 and many of these areas, which are
not habitable, lie at relatively low latitudes where the sun's rays
are strong.

The Nile valley, a winding green ribbon of amazing beauty and cultural
magic coursing through often staggering scenery, is bounded on each
side by thousands of square miles of empty desert on which a positive
torrent of solar energy--of the order of 400 watts per square
metre24-- beats down year after year to sink unharnessed in the sand.
A yearning for clean air in our cities and an end to exhaust pipes
does not entitle us to too much wishful thinking about the future, but
the thought of this country trading with Egypt for totally clean
Saharan electricity does have its appeal, for the new non-carbon
technologies may well become crucial. Economic factors will no doubt
largely determine the outcome, but when London is clogged with
electric cars the bicycle will still be needed by travellers who wish
to move freely.

Using their own language

The officials of the NHS will not so far have found this article easy
reading. Papers in a foreign tongue are always difficult, and we must
therefore address some words to them in their own language. No civil
servants with time on their hands and a need to fill their day or
their page will say "use" if they can say "utilise" or "see" if they
can say "visualise" or write "start" if they can spell "initiatise."
So we must above all eschew monosyllables, even though some of the
most charged and poignant lines in all Shakespeare consist of nothing
else--but then he had something to say.

The phrases which follow--though altered in sequence--have all come
through our practice's letter box from official sources in the past
four years, and the sighting of any one of them has regretfully meant
the immediate despatch of the whole document to the waste paper
basket, for our hours are long and our time precious, and our reading
has to be selective. No working doctor can ever be entirely at ease
when dealing with the defensive, stale inertia of a hostile,
overmanned and self regarding bureaucracy, but we have to try, for it
has the NHS by the throat.

So, to our administrators: "The mediation of inter-personal
expectancies in the helper-helpee professions has to be
visualised"--you will agree --"in the context of a shared

understanding of user empowerment. The a priori decision making
process will be facilitated by an integrated approach using an optimum
skill mix, and uniform guidelines will help to underpin and complement
the process of change. There must be a perceived need to develop
finely tuned coping skills within a problem solving and goal setting
framework and a supportive environment. By a layered approach, ongoing
in-depth strategies will be developed utilising a meaningful protocol
of interactive and proactive progressive modules, in which the
subjects will be taught didactically and analysed from the
collaborative viewpoint. Unfortunately, due to slippage of some of the
planned projects, the intended prioritisation of goals may not be
achieved, and the necessary initiatisation and pump-priming may have
to be postponed, particularly in the development of consumer-facing
skills within the primary care setting and the understanding of
children of their place and involvement within the
dependency-independence continuum."

Such turgid, pretentious, even preposterous prose has nothing whatever
to do with the clinical care of patients and indeed interferes
inexcusably with good medical practice, for it and its authors have
deflected huge public funds from the known and often desperate needs
of ill people and their families. Ask any general practitioner,
hospital doctor, or nursing nurse.

George Orwell was right: "The great enemy of clear language is
insincerity . . . When the general atmosphere is bad, language must
suffer." He further observed: "If thought corrupts language, language
can also corrupt thought."25 In Utopia this essay on the writing of
clear English is required reading for all government officers; the
need for it in present day Britain is obvious.

But to return to the real world in which we and our patients live. We
too must look to our credibility, for if as general practitioners we
tell our patients to exercise while we continue to crawl round central
London cushioned in our cars--the repeated excuse for our late arrival
being the traffic or the parking--we could well attract the fair
retort: "Physician, wheel thyself."

Concorde; bicycles; inertia

The amount of petrol that I have saved in my 87000 km (54000 miles)
and 22 years of cycling--an average of only 14.5 km (9 miles) per

working day--is of course derisory, and hardly worth mentioning. It is
approximately 10000 litres, and this volume of fuel is burnt up in 23
minutes--at 7.3 litres a second--by Concorde flying supersonically at
2172 km (1350 miles) per hour. Unlike the cyclist, Concorde's fuel
consumption varies considerably--from 24 to 18 tonnes per hour--as it
burns up its kerosene and gets lighter, and assuming a payload of 100
passengers this averages out at just over 7.7 km (4.8 miles) per litre
per passenger. At subsonic speeds, for aerodynamic reasons, the fuel
consumption is considerably greater. Cyclists do rather better. In
terms of petroleum equivalent their use of energy works out at well
over 353 km (220 miles) per litre,26 and in fact is nearer 495 km (310
miles) per litre. Yet my bicycle does have one thing in common with
Concorde--nobody, so far as I know, has ever accused either machine of

In general in this paper I have been discussing inertia in its current
colloquial connotation of lethargy or sluggish movement, but its
strictly scientific meaning is "that property of a body by virtue of
which it opposes any agency which attempts to move it, or, if it is
moving, to change the magnitude or direction of its velocity." It is
ironic that this scientific definition applies most nearly to the
least logical and rational of all the groups which we have discussed.
The discerning reader will need no guidance as to which group this is,
for it is clearly not the ancient Romans and neither is it Neanderthal


But I have been fortunate. I entered medicine when the NHS was newly
established, and for 35 years it was a privilege to work in it--though
not any more. This civilised and once hopeful ideal was put in hand at
the end of a long and punishing war by a country which had suffered
much, and which, perhaps because of this, was less attuned to greed
and more to pity than the generation that now lays down our
priorities. It is sad to see its gradual strangulation and the
pitiless downgrading of its services.

The Romans, too, had assets of some value before their civilisation
also declined, and not least an exemplary clarity of language. In a
previous paper I suggested that modern Homo sapiens was beginning to
evolve, at least in cities, into two distinct subgroups Homo se
propellens and Homo (urbanus) vehiculo constrictus.4 Perhaps we should
now widen this latter subgroup to Homo urbanus inertia constrictus, a
term which time will quickly shorten to plain Homo constrictus.

We do not yet know whether it will be the construction of their
environment, their arteries, or simply of their outlook on life that
finally does for these pitiable creatures. It could well be a
combination of all three, but their enfeebling inertia will lessen
their numbers and by end of the Holocene they will be gone. There is
every reason to hope that Homo se propellens (and Puella se
propellens) will survive, and they will deserve to. They will walk, or
run, or ride their bicycles. They will not pollute. Their fuel will be
endlessly renewable whether it be caviar, cucumber, or chips, and the
key to the future will be in their hands.

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