New Uses for Transport Statistics
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THE railways' share of total inland goods traffic felt from about 60 per cent. in 1938 to 44 per cent. in 1958 and to about 42 per cent. in 1959, said Mr. K. F. Glover, of the Ministry of Transport, in a paper, "Statistics of the Transport of Goods by Road," before the Royal Statistical Society in London last week.
No doubt some traffic which had previously passed by rail had been lost to road vehicles, particularly since 1951, but the railways were still carrying more traffic than they were in 1958, and by far the greater part of what was now carried by road was new 'traffic.
An adequate statistical system covering the transport of goods by road was needed to serve a variety of economic and administrative purposes. Information was required about the structure of the industry, the development of its various component parts, the patterns of operation and the nature of goods being carried. These aspects were not likely to change materially in a short period.
Prompt Measures
Total output of the industry, relative to the traffic carried, might alter substantially from time to time, requiring frequent and prompt measures. A large proportion of vehicles was in very small fleets, and a representative picture could not be built up on the basis of returns from operators of large fleets.
In exploring other methods, of obtain-ing information there were two different lines of approach. Inquiries involving the collection of returns from operators of a sample of vehicles were used to throw light on. the internal pattern of the industry and the amount of work being done at the time the samples were taken.
Alternatively, counts could be taken at points: on roads selected at random to obtain current indications of the changes in the total volume of work being done by goods vehicles.Attempts could then be made to combine the results of .these two approaches with the available statistics of railway freight to give estimates of the total volunie. of inland freight traffic. The relationship between these and changes in other indicators in economic activity could then be discussed.
Sample Inquiry
. Commenting on the classification of C-licence vehicles in a sample inquiry according to the nature of the operator's main business, Mr. Glover said that the distributive trade and various types of construction work accounted for over half of them. If the food, drink and tobacco industries were also taken into account, nearly two-thirds of the smaller vehicles were covered and about threefifths of the larger ones, Mr. Glover claimed that sample inquiries carried out by the Ministry in 1952 and 1958 gave a fair amount Of information about the road goods transport industry at a point of time, though their duration was brief. But there were B12 two objections to taking samples more frequently in order to •obtain a continuous series.
The amount of work involved in selecting the sample, in issuing, collecting and scrutinizing the forms and collating the information was, in practice, too great with moderate staffs to provide a monthly or quarterly series.
In the inquiry taken in 1958, a continuous series of manual counts was begun at 50 points, so designed as to give estimates of the changes in aggregate vehicle mileage performed on the roads from one month to the next by each major category of motor vehicle. The counts extended over 16 hours from 6 a.m. to 10 p.m.
Night traffic was not missed, however, in the" sense that it was omitted from the estimates of aggregate traffic, it being assumed that such traffic was a constant proportion of the whole. Counts taken on 411 days of the week suggested that goods traffic from Mondays to Thursdays did not differ by more than 1 per cent. from .that on Fridays.
It therefore appeared safe to regard the data from the 50 point counts as being a broadly reliable .indication of monthly changes in the total vehicle mileage by vans and lorries. The final step was to use the information as an indica tor of changes in total traffic in the sense of ton-mileage. This was probably less hazardous than it might appear.
It could be said thatthanges in vehicle mileage might give an unreliable indication of changes in ton-mileage, because no account was taken of variations in vehicle load factors, but this was not substantiated on closer examination. Twothirds of the total ton-mileage of road transport was accounted for by " end-toend " traffic—work which involved picking up a load at one point and putting down the whole of it at another_ It was a feature of this class of work that changes in the volume of traffic would be fully reflected in vehicle mileage.
It was a characteristic of road transpoft that operation was flexible. Vehicles rarely ran to a timetable and if an adequate load was not forthcoming, other arrangements were made to avoid uneconomic running.
Fairly Steady
Frequent inquiries would obviate the danger that errors might accumulate through changes in the average gize of vehicle. In the past few years the average unladen weight of goods vehicles had remained fairly steady, but the ratio of carrying capacity to unladen weight might have increased. Such changes occurred only slowly, and any error could be eliminated by re-basing the series on fresh inquiries every few years.
It was interesting to try to relate the change in the total volume of inland " goods transport to changes in the economy at large, but difficulties arose in measuring both transport and production. Increased levels of production often required materials to be drawn from wider. areas and the products to be sold at more distant points. Economies in industrial processes could lead to the geographical extension of markets, and the cheapening of transport facilities would operate in the same direction.
Goods in Pipeline
Fluctuations in goods transport might give information about changes in the economy which could usefully supplement other economic indicators. The volume of goods being carried would reflect changes in sectors of the economy not covered by an index of production, such as agriculture, and would also be affected by the movement of goods in the pipeline to merchant and retailer. In addition, an index of transport provided a quick indicator of changes in economic activity.
An index of transport activity could be a valuable short-term economic indicator in its own right, It could be of wider scope than an orthodox index of industrial production, and it could be prepared more easily and quickly than many other economic statistics. But it was desirable to have some experience of the 'behaviour of the transport series before deciding exactly the use to which it could be put. It was to be hoped that transport statistics would become more closely linked to general economic statistics in the same way that transport was interwoven with all economic activities.