Opinions and Queries
Page 42
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Do They Understand Statistics ?
1F you were wrong in your conclusions of the efficiency of the Road Haulage Executive, it is quite certain that I. H. Brebner, in his letter in your issue dated April 4, does nothing to prove it. In fact, the example he quotes does little but show that he is abysmally wrong. Not for the first time, I ask: Do these British Transport Commission people who publicly interpret transport statistics really understand them?
An increase in ton-mileage of itself means nothing at all. Ton-mileage when meaning payload mileage, that is the tonnage of goods requiring to be carried multiplied by the distance between the places to and from which they require to be carried, has no significance.
Efficiency is measured by relating payload tonmileage to other factors, of which mileage is only one. If Mr. Brebner is endeavouring to measure efficiency by the vehicle load he cannot ignore empty mileage, at least in any overall average picture. The statistic for which he is apparently feeling (and it is not the best) is average net ton-miles per vehicle mile (total vehicle miles, that is, not merely loaded vehicle miles). He must, therefore, divide his total net ton-miles by the total of vehicle miles-100,000 by 24,000 and 108,000 by 24,500. The improvement is 0.0055 per cent.
Even that is dependent on -another factor, namely, capacity ton-mileage. If the capacity ton-mileage of his first example were five tons multiplied by the total mileage, the ratio of net ton-miles would be wonderful. If the capacity ton-mileage of the second example required to attain an average per loaded vehicle of 5.33 tons, were six tons multiplied by the total mileage, load efficiency would be much inferior to the first example.
Pursuing efficiency statistics still further, vehicle mileage is really of itself a very poor test. Vehicle hours are much more reliable, and in my opinion the best summary figure to give a short comparison to enable the administration to judge the general trend, is net tonmiles (computed from consigning documents or waybills) per vehicle hour. From this, inquiries about changes would be directed to other comparisons, e.g., with capacity ton-miles per vehicle hour, net ton-miles per vehicle mile, capacity ton-miles per vehicle mile.
In his fourth paragraph, Mr. Brebner recognizes the fallacy of his own examples; and in his fifth, he indicates the figures which show an improvement of 0.0055 per cent. (as I mention above) without pointing out the enormous difference between this figure and the 8 per cent, improvement which he claims is illustrated in his own example.
Vehicle miles, as Mr. Brebner recognizes, is a valid statistic only if every vehicle mile included is of equal capacity value. Periodical figures of total vehicle capacity (weight and cubic) are 'quite reliable in relation to net ton-mileage over the same period, for they will reflect changes if carefully compiled.
Northwood, Middlesex. FREDERICK SMITH.
PUBLIC AND PRIVATE ECONOMY
ON several occasions recently l have read in your journal information regarding provincial bus operators who, in an effort to mitigate the constantly rising cost of operation, have rebuilt and brought up
to present standards their war-time utility buses. Many of these vehicles were Guy Arabs with Gardner 5LW engines, and were of undeniably sound construction, except for the war-time coachwork. Despite this, I have noticed that London Transport is disposing of some hundreds of them, although going to considerable trouble and expense to rebuild pre-war types.
Whilst the policy of fleet standardization has, no doubt, much to commend it, nevertheless it seems to me to be most illogical to dispose of vehicles which have a potential chassis life of many years.
I have had considerable experience of Guy Arab vehicles while working with a company of the Tillings Group, and I never saw one break down during the two years I spent there. Also the workshops staff spoke well of the general construction of the chassis.
One aspect of standardization which is seldom mentioned is that should an inherent fault develop in a particular model, this may cause far more trouble when a thousand or more are operated than would have been the case had the operator decided to run a more mixed fleet.
Recently I observed, with some amusement, the 'flap" which ensued when a bus operated by one of our largest groups developed a severe crack in its frontaxle beam. This made it necessary to call hundreds of similar vehicles off the road in order that they should be examined.
London, W.I3. E. J. COOKE.
TRAINING FOR MAINTENANCE ABROAD
A LEADING article headed Training for Main
tenance Overseas" in your issue dated April 4, refers to the efficient maintenance of British vehicles abroad, whether in the Commonwealth or in foreign countries, as being a matter of the highest importance to the export drive. Also mentioned in this article was the question of training engineering graduates from these countries, who will eventually have a powerful influence in increasing the popularity of British vehicles abroad. It would certainly be of great benefit to the operators themselves if they had factory-trained • engineers to maintain their vehicles.
Aspiring to become a qualified maintenance engineer, I came to this country last August and am training as a student engineer (unpaid) with the transport department of the Bournemouth Corporation. I am a graduate mechanical engineer from the University of Calcutta and would• be glad to learn full details of the scholarship scheme inaugurated by the Federation of British Industries. Perhaps this would help me to achieve my ambition to take an executive position in the road transport services of the Government of India, the vehicles in which are predominantly British.
Bournemouth. H. A. SINGH.
[We are afraid that this correspondent will be disappointed to learn that he is not directly eligible as a trainee under this scheme, as the scholarships are made available in India by arrangement with the Government there, through an Anglo-Indian Selection Committee in New Delhi. He could, however, forward particulars of his case to the High Commissioner of India, India House, Aldwych, London. W.C.2.—ED.]