THE DOPPLER EFFECT

12th May 1967, Page 192

12th May 1967

Page 192

Page 192, 12th May 1967 — THE DOPPLER EFFECT

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MOST people at some time or another, standing on the platform of a lonely railway station while an express rushes by, have noted how the whistle rises to a shriek as the engine draws level with them and fades away with a melancholy dying fall as the train disappears in the distance. In the long interval of quiet which follows they may also speculate on the curious fact that the driver would have heard no change in pitch. The same sound has produced two very different effects.

The familiar incident might almost be a parable with an up-to-date application. To the people concerned with running them the railvvays seem to be making steady progress with new techniques and new developments. To a large section of the public they seem in inexorable decline, losing more traffic and more money each year. Both apparently contradictory opinions may turn out to be two aspects of the true situation. What is lost on the swings will be gained on the roundabouts. That at least could be the view of the Government.

STRANGE BEHAVIOUR The strange behaviour of the sustained note when it is moving away from the listener is known to scientists as the doppler effect. It is said to apply to rays of light as well as to sounds. The shift in the light from distant galaxies towards the red end of the spectrum has led astronomers to the theory that the whole universe is expanding and that the remote stars are rushing away from the solar system at an ever-increasing speed.

The dizzy sensation which such a notion is bound to arouse may recall the reaction in the years following the war to the rapid and accelerating increase in the number of vehicles on C licence. Although not astronomical the figures were large enough. From 306,000 in 1945 the total rose to 383,000 in 1946, even more quickly to 487,000 in 1947 and to 591,000 in 1948. Here if anywhere there seemed to be a terrestrial parallel to the expanding universe and no doppler effect was required to measure it.

INCREASE RATE FELL In fact the process did not continue indefinitely. The annual rate of increase fell from over 100,000 to about 60,000 and in 1951 to about 30,000. From that time the pace varied although each year saw an increase of some size. In 1965 it was as low as 7,000; and in 1966 for the first time on record there was a drop in numbers from the high point of 1.319,000 to a total of 1,245,000 which was the lowest since 1962.

Somewhat surprisingly no great notice has been taken of this unique event first made apparent in an appendix to the annual reports of the Licensing Authorities. The hauliers— whose total vehicle strength incidentally has been climbing slowly but steadily year after year—and the railways might have been expected to celebrate what could be interpreted as an opportunity for taking more traffic. The politicians who have twice drastically changed the course of road transport since the war might have wrangled over the credit for finally stemming what was once regarded as a dangerous flood.

At that time there was one widely accepted explanation of the phenomenon. There were many possible reasons. The shortage of vehicles during the war was bound to mean a rapid growth in their numbers as soon as they became more generally available. The revival of peace-time trade and industry also stimulated the demand for vehicles. Apart from these special factors the expansion of road transport was a process which had been continuous since the 1914-1918 war and was likely to continue once the controls were released.

INCREDIBLE INCREASE

What most people preferred to believe was that traders were buying more vehicles to escape the consequences of the nationalization of long-distance road haulage. To the Conservative Opposition it seemed to follow naturally from the legislation which they had so bitterly opposed. To many of the supporters of the Labour Government the almost incredibly rapid increase in the C-licensed fleet was proof enough that trade and industry were prepared to sabotage nationalization before they had given it a fair trial and that it would have been wiser to impose restrictions on all types of licence.

Undoubtedly the 1947 Transport Act was the reason why many traders put their own vehicles on the road. They saw no other remedy when the special service they had received in the past was no longer available to them. There was no particular political bias in this. Fortunately the representatives of the C-licence holder were able to make this clear and to keep the Government of the same mind. There were individual left-wing protests but no serious concerted effort to clip the wings of the private carriers even when they were putting nearly 10,000 extra vehicles on the road each month.

That the process of deceleration coincided with the return of long-distance road haulage to free enterprise was too much of a coincidence for the Conservatives not to take full advantage of it. As time went on, however, the political overtones became less and less appropriate. The lack of any great stir caused by the drop in the total last year must be interpreted as a good sign. The C-licence scale is no longer used for taking the temperature of the transport situation.

A USEFUL GUIDE As time goes on it might be found useful for other purposes. Economists, industrialists and politicians continually seek ways and means of measuring the state of the nation. They must often rely on estimates about which there is considerable uncertainty. The number of vehicles operated by traders in any given year might be a useful guide to the progress of the economy. A reasonable rate of increase year after year could be a reliable sign of a corresponding increase in production.

Not that the calculations can safely be simplified to this extent. The drop in numbers in 1966 may not have meant a drop in the total payload. No breakdown is given in the Licensing Authorities' reports, but the figures for hauliers show substantial increases in all categories of unladen weight above 4 tons and there is no reason to suppose that the trend would be any different for the C-licence holder.

Other unknown factors include the extent to which traders with unsatisfactory facilities for maintenance were encouraged to put their transport out to hire by the increasing risk of prohibitions and possibly prosecutions and by news of the more stringent safety regulations shortly to come into force.