IS THE TON VILE WORTH• WHILE?
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REGULAR readers of these articles are aware that, in my view, it rarely happens that the cost per tonmile can be ascertained with any degree of accuracy without statistical work out of all proportion to the value
of the results. .
What is a ton-mile? It is the work done when one ton is moved through one mile, or two tons are moved half a mile, or half a ton is moved two miles. In other words, when moving a load, the work done is the product of the weight moved, by the distance it is moved. If the weight be quoted in tons and the distance in miles, the answer is in ton-miles.
Thus, a lorry and load weighing eight tons runs from London to Manchester, say, 200 miles. The work done is calculated by multiplying eight tons by 200 miles and the answer is 1,600 ton-miles. '
Those who study "The Commercial Motor" road tests will be familiar with the term, On page 74 of "The Commercial Motor" dated February 20, for example, there appears a road-test report of the A.E.C. Matador. In the data pane), under the heading "Fuel Consumption" is given the following information: " 12.32 mpg that is, 149.8 gross ton-m.p.g." The non-technical readers may well ask, "How does one arrive at that figure of 149.8 gross ton-m.p.g. ? '
In another section of the data will be found information as to weight of chassis, load, passengers, etc., indicating that the running i.e., gross weight, was 12 tons 3 cwt., which is 12.15 tons. The work done by that vehicle, from the consumption of one gallon of fuel oil, is, therefore, 12.15 tons multiplied by 12.32 miles, which is 149.8 gross ton-miles.
Data for Engineers and Managers
Now, that figure of 149.8 gross ton-m.p.g. is useful to engineers and transport managers; it is a measure of the performance of the vehicle, a standard of comparison. But the figure serves only as a standard of comparison between the A.E.C. Matador and other vehicles of similar type and load capacity. Let me now refer to another road test, this time of an Austin 25-cwt. van (see "The Commercial Motor," November 7, 1947). Oh a straight test the petrol consumption was at the rate of 17.42 m.p.g., and the gross, or running weight of the vehicle and load was 2 tons 13 cwt., i.e., 2.65 tons. The gross ton-mpg. was, therefore, 2.65 multiplied by 17.42 miles, or 46.5. There is a tremendous difference there, yet both performances are excellent.
The all-in cost of the A.E.C., running 800 miles per week, will approximate to 9d. per mile. On a run to Manchester from London, therefore, the cost would be £7 10s, and the gross ton mileage would be 12.15>200=2,430. The cost per gross ton-mile would thus be 0.74d. The cost of the Austin, under similar conditions, would be about 64d. per mile, and the cost of the run to Manchester, £5 8s. 4d. The gross ton-mileage would be 530 and the cost per gross ton-mile is 2.45d.
What the Operator Wants
Now we have to realize that the operator is not at all interested in the cost per gross ton-mile. He is only concerned, if at all, with the cost per ton-mile of the useful load he carries, which I might call cost per payload ton-mile. In other words, taking the big lorry, he has carried 8 tons, and not 12.15 tons, over 200 miles. The total cost is still £7 10s., but the ton mileage is now only 1,600, and therefore the cost per ton-mile, so far as he is concerned, is £7 Ws. divided by 1,600, which is 1.13d. per ton-mile and not 0.74d.
In the case of the smaller vehicle the payload is 11 tons. The payload ton-mileage is 250 and the cost is still £5 8s. 4d.; the cost per payload ton-mile is 5.2d. and not 2.45d., as given above.
I will admit it is not likely that any operator would be running 8-boners and 25-cwt. vehicles more or less side by side on regular journeys from London to Manchester. It is not, however, unusual for a concern to have vehicles of varying load capacities covering the same route, especially if the loads vary from time to time. It would not be strange, for example, for the same concern to be running over this one route I5-tonners, 8-tanners and 6-tonners.
Now, comparative operating-cost .figures for those three A36
types of vehicles, assuming them all to be oilers, will approximate to Is. 2d., 9d. and Md. per mile, and the costs for the 200-mile run would be ill 13s. 44:1.. £7 10s. and
16 17s. 6d. respectively. That would be for payload ton-mileages of (a) 15 x 200, which is 3,000; th) 8 w 200 (1,600); and (c) 6 x 200 (1,200).
Working out the cost per payload ton-mile on the basis of those figures, we have for the 15-tonner, 0.93d., for the 8-tonner, 1.13d., and for the 6-tonner, 1.38d. What is this operator to take as his figure for cost per ton-mile for that traffic? You might think he would take an average figure, but that would not do at all 'Before he could get an average figure he would have to take from his books the number ot journeys run per annum with the 15-tonner, the number with the 8-tonner, the number with the 6-tonner, work the total cost out for each and then average the ton-mileage for the load. Even that figure would be of little practical use.
It might be suggested that those figures for comparative cost per payload ton-mile would he useful in arriving at the values to the operator of the various sizes of vehicle.
That is not the case. Even the least knowledgeable operator will be well aware of the fact that over a specific route the cheapest vehicle is the one which carries the ,biggest load, and that is the 15-tonner, and he does not need to go into any complicated calculations about tonmileage in order to assure himself that that is so.
Salting Vehicle to Traffic Moreover, he uses these different sizes of vehicle, as I have already pointed out, because one week he may want to carry 15-ton loads, another week only 8 tons, another 6 tons, and so on. He wants to be able to suit the size of vehicle to the quantity of traffic offered and is, therefore, not concerned with the comparative payload-cost per ton, mile of each.
It often happens that on, say, a 15-tonner an operator wants to carry 10 tons or 12 tons. If he carries only 10 tons on the 15-tonner, the cost for the journey is practically the same, but the cost per payload ton-mile is 2.8d., and if he carries 4 tons on the 6-tortner, to take another case, the cost per ton-mile becomes 2.06d. instead of 1.38d.
Moreover, there must very .few operators indeed whose business is confined to one straight journey, as from London to Manchester and back again, without having alternate routes to cover. What is he going to do about that? He will need to work out not only a different cost per payload ton-mile for each type of vehicle used, but also a cost per payload ton-mile for each different journey, for that will differ accordingly.
And again, and this is perhaps the real crux of the problem, what is he going to do in the case of a journey such as the following—once again from London to Manchester. He starts from London with a 15-ton load. Arriving at A, 40 miles away, he drops 4 tons. Running from A to B, a further 30 miles, with an 11-ton load, he picks up 3 tons, and with that 14-ton load runs a further 60 miles to C. There he drops 8 tons and picks up 2 tons, completing his journey to Manchester with that balance of 8 tons, At Manchester he unloads completely and picks up 10 tons. He brings that for 120 miles on the way back to D, where he drops 6 tons of it, and brings 4 tons for the remaining distance of 80 miles from D to London again. How are we going to deal with that in trying to assess the cost per payload ton-mile?
First of all, 15 tons for 40 miles, from London to A, is 600; next, 11 tons for 30 miles, from A to B, is 330; from
B he .carried 14 tons. 60 miles to C, that is 840 ton-miles, and completes the run from-C to Manchester carrying 8 tons for the 70 Miles still remaining, that is 560 ton-miles. Returning the first stage of the journey is 120 miles to D carrying 10 tons; that is 1,200 ton-miles, Finally, from D to London, 86 miles, carrying 4 tons, is 320 ton-mites. Add those up and we get 3,850 payload. ton-miles. the cost, presumably is still Is. 2d. per mile, and for 400 miles that is 5,600d. It would seem that the cost per ton-mile is thus 1.45d. But-is it?
Let me work it out again, this time bringing cost into it. The first stage is 15 tons for 40 miles at a cost of 560d.
That is equivalent to 0.93d. per payload ton-mile, and that is what it actually costs to deliver the 4 tons of traffic which is dropped at A. • • . . .
Next, the 11 tons from A to 13 for 30 miles costs 4.20d, for the 330 payload ton-miles, that is, 1.271 per ton-mile. But we should remember that that 11 tons has really travelled 70 miles, of which the first 40 miles was at 0.93d. per ton-mile and the next 30 miles at 1.27d. per ton-mile.
The average cost per ton-mile is thus . 40 s. 0.93 plus 30 x 1.27, divided by 70, so that the average would seem to be 1.07d.
I say, " would seem to be," because I am very doubtful whether it is correct, mathematically, to average the cost in that way.
From B to C, a distance of 60 miles, 14 tons are carried, which is 840 ton-miles, at a 'cost of 840d, so that the cost per ton-mile for that stage of the journey is Id. per ton-mile, Finally, the last stretch, from C to Manchester, carrying 8 tons over 70 -miles, costs 980d., which is equivalent to 1.75d. per ton-mile.
What do these mean? Is there one of them that fairly indicates a cost per ton-mile for any consignment, and if so, which is the figures that applies?
Demonstration of Absurdity
Perhaps the most effective way to show the absurdity of it is to take the 6 tons which stays on the lorry throughout the whole journey and is never disturbed. For the first 40 miles of its journey that 6 tons had travelled at 0.93d. per payload ton-mile; for the 30 miles, 1.27d. per ton-mile; for the next 60 miles, Id. per ton-mile, and for the remaining 70 miles at 1.75d. per ton-mile.
What then is the cost per payload ton-mile of conveying those 6 tons? Is it a total or• an average of these four figures? It cannot be the total and, as a matter of fact, I think I can show that it cannot be the average, which is actually 1.24d. per ton-mile.
If we must try to get an average figure—for what it is worth—we must take first the cost of the 40 miles at 0.93d.,-which is 37.2d.; say, then, 30 miles at 1.27d. (38.1d.), 60. miles at Id. (60d.), and 70 miles at 1.75d. (122.5d.). The total is 257.8d., and over 200 miles that is 1.29d., differing, therefore, from the 1.24d, already obtained. Nevertheless, I think that if an average applies at all, the I.29d. is more nearly correct than the others.
Is it reasonable to expect that calculations such as this should be made for every journey covered by every vehicle belonging to that operator running not only to Manchester, but to Birmingham, Leeds, Hull, Cardiff, Southampton, and so on, bearing in mind the fact that it is probable that no two journeys are alike?
A practical example, one which does afford some reasonable basis for use of the ton-mile figure, if ever there be such an occasion, lies before me. It relates to a concern which has two depots, one at London, one at Manchester. The goods are distributed in containers from those two main depots to, among other places, Cardiff and Birmingham from London, Leeds and Hull from Manchester. I have not precise details of the weights, but the following are reasonable assumptions. A container, fully loaded, weighs 8 tons. Of that, 1 ton is the net weight of the container itself, 5 tons the net weight of the goods carried and 11tons the net weight of the cases in which the goods are packed. Those cases form the return load in every ease.
The point is, therefore, that from Manchester and from London the vehicle goes out 6arrying a gross payload of 8 tons, of which, however, only 5 tons is net useful load. It returns from each journey with a load of 2 tons, comprising 1 ton weight of container and lè tons weight of eases. the net useful payload, however, is no more
than 5i tons carried on the outward journey Now let us see how we can utilize these figures as the basis for assessing cost per payload ton-mile on four typical journeys.
• A 160-mile Journey
First, from London to Cardiff, which I will take as being 160 miles. The travelling time should average 10 hours, and allowing one hour to remove the container, the total day's work in the outward direction is 11 hours, followed by a similar 11 hours next day in order to complete the task.
For the first day, at 9d. per mile, the cost of operating the vehicle will be £6. To that must be added 9s. for overtime and 9s. for subsistence allowance, making E6 18s.
On the return journey there will still be 16 for travelling and an hour for overtime, but, of cpurse, no 9s. for subsistence. The total cost will thus be 113 7s, The net payload ton-mileage, however, is only that of the outward journey of 160 miles carrying 5f tons. The payload tonmileage is; therefore, 880. If 880 be divided into £13 7s, the result is 3.64d. per payload ton-mile;
Now take the case of London to Birmingham at 110 miles. On this occasion the:outward travelling time will approximate to seven hours, and if I take, as before, one hour for terminals, that gives me eight hours. The cost of the outward journey at 9d. per mile will be £4 2s 6d., to which must be added 9s. for subsistence, making £4 11s. 6d. Cost of the return journey will be £4 2s. 6d., and the total cost £8 14s.
3.45d. per Ton-mile The ton-mileage J is that resulting from the carriage of 5i tons net payload for 110 miles, which is actually 605 payload ton-miles. Divide that into £8 14s., and it gives me 3.45d., which is the cost per payload ton-mile.
Manchester to Leeds is, of course, a short journey48 miles 'approximately—which means that a return journeywill be completed with loading and unloading in an "eighthour day The cost of the journey is 96 miles at 9d., which is £3 12s. The ton-mileage is 5i multiplied by 48, which is 264 ton-miles, and the cost per payload ton-mile is 3.65d.
Finally, if I apply the same method of calculation for the journey to Hull I shall get 3.66d. Clearly, the cost per ton-mile for this particular job is approximately 3.65d..
which can be taken to cover all the journeys. S.T.R.