More About the Ton-mile
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Further Arguments Against the Tonmile as a Measure for Assessing Costs and Rates
BEFORE proceeding further with the argument I started in the previous article, to show how infrequently the ton-mile is of any practical use to the haulier. I think I should explain what is meant by the term, ton-mile.
In a previous article I described it as the work done when one ton is moved through one mile, or two tons through half a mile or half a ton moved two miles. To put it another way; the work done when moving a load is to be calculated by multiplying the weight moved by the distance through which it is moved. 'The weight should be assessed in tons and the distance in miles. Thus, a fully loaded eight-wheeled lorry, tipping the scale at 22 tons, moving a distance of, say, 200 miles, will involve work done to the tune of 22 multiplied by 200, that is, 4,400 ton-miles.
The term ton-mile is of considerable use to engineers because it is a measure of the work a vehicle does when it performs any task. In that way, it can be employed to compare the capabilities of one vehicle withlhose of another of the same type and size. The expression figures in all the test data published in this journal from time to time. In The Commercial Motor" dated March 18 of this year, for example, the test results obtained from a trial of a Foden lorry are given. The figure of 256.2 gross ton-miles per gallon appears in the eata quoted. It is also stated that the fuel consumption was at the rate of 11.51 m.p.g. Let me use these figures to clarify the definition of the ton-mile as set out above.
It should be clear that the vehicle runs 11.51 miles for every gallon of fuel consumed. It is also stated that the gross weight of the vehicle as tested was 22 tons 5 cwt., made up of 6 tons 19 cwt. I Clr., the unladen weight of the vehicle itself, plus 15 tons 0 cwt. 3 qr. actual payload, plus 5 cwt., for the driver and observers. The point is that in travelling the 11,51 miles there was 11.51 multiplied by 2225 tons of work done, that is, 256.2 ton-miles, for one gallon.
Useful Only for Comparison
a This figure of gross ton-miles per gallon is very useful to
the engineer for purposes of comparison, but it is not the sort of information that is wanted in connection with the assessment of the value of the vehicle as a conveyor of goods. The figure wanted therels the pay-load ton4nileage. In order to obtain the "payload ton-Miles per gallon" we need only the 15 tons 3 qr. and can ignore the .unladen. Weight Of the yehicle, -also the weight of driver and observer's. The work done for the eipenditure of a gallon of fuel.ii now, therefore, 15.0375 tons by 11.51 miles, which
_ is 113 payload ton-Miles per gallon.
Now to convert that term into figures which will interest the haulier. Suppok that he is running the Foden on trunk services which involve a weekly mileage of 800. A single journey is from London to Manchester, 200 miles, on which the payload ii actually 15 tons. The operating cost per Mile is Is. The total operating cost of a single journey is thus £10. The payload ton-mileage is 15 times 200, which is 3,000. The cost per ton-mile is therefore LIO divided by 3,000, which is 0.8d. So long as the vehicle carries full loads of 15 tons,-thae cost per ton-mile will remain at that figure. But now suppose that, on the return journey, the vehicle carries only 8 tons. The cost of the trip is still, as near as makes no matter, the same. So long as we are working on average figures that is. per tnile holds good. The payload ton-mileage is now, however, only eight times 200, that is, 1,600. The cost of the journey is still £10, so that the cost per ton-mile is now lid.
One of the points I always raise against the ton-mile as a measure of the work done by a haulier, and as means for assessing charges, is that if it is to be applied with any degree of accuracy, the calculation must be made anew for nearly every journey, and even for parts of a journey. I have shown, in the two examples above, how great the difference can be as between an outward journey and a return. Even if the work be as straightforward as that, the sum must still be done each trip; it will seldom happen, first, that the outward load is always 15 tons or that the return load is 81 8 8 tons. They will probably differ load by load and week by week. The position is much worse when a vehicle makes calls on the way, dropping part loads and picking up loads as the journey progresses. Trips which involve that sort of thing would become a headache for the operator and he would have to employ a statistician to keep pace with the work involved.
In the previous article I gave some ordinary everyday examples of work done by hauliers showing that the tonmile was rarely asked for and as rarely applicable as a
rneans for assessing costs and rates, will pursue that part of my argument a little further. '
When Ton-miles Mean Something One of the simplest jobs to cater for is the haulage of compressed gas cylinders. They weigh practically the same when full as they do empty. Moreover, the vehicle is nearly `always loaded to its normal capacity throughout the journey. And that applies even when, as is usual with this traffic, the haulier is called upon to make a round journey, dropping a few cylinders here and there, picking up empties at the same time. There, if at all, the ton-mileage, figure would mean something. If the vehicle cover 500 miles per .week and cost, a shilling a mile to operate, the weekly cost is £25. If the load carried all the tirne is 5 tons, then the weekly tonmileage is 2,500 and the cost per ton-mile is thus 2.4d. Rut who wants to know the 'cost per ton-mile? Not the customer; he Wants to know what he will have to bay per cylinder. And if the customer is not interested, neither is the operator, and that's that.
The next letter from 'my files did involve an inquiry as to the rate per ton-mile: let us go into this fully. The inquirer wrote to tell me he had just purchased a couple of five-ton lorries of well-known make, for which he had paid £450 each. They were second-hand, of course. He is paying his drivers the regulation wages, uses, he states, a gallon of petrol every ION miles Mud a gallon of lubricating oil every week, during which each vehicle covers 250 miles. He wants what he calls a "basic rate" per week and per ton-mile. He states that his average load will be four tons..
I told him that his rate per week would have to be £20 12s., which is the figure quoted in "The Commercial Motor" Tables of Operating Costs. Or, rather, it is the mean of the amounts-quoted for a 200-mile week, £19 8s., and for a 300mile week. £21 16s. I also informed him that the total net operating cost of the vehicle would be £14 Is. per week (taken from the Tables in the same way). The difference between the charge and the cost, £6 I Is. per week, is to cover establishment charges and profit. (I deemed it necessary to warn him that it was not all profit.)
I told him that I could not give him any figures for th.! cost or charge per ton-mile unless I knew more accurately what his actual loads were, how they varied from day to day, or even from mile to mile, and for what percentage of its time the vehicle ran empty.
I have not yet had a reply to my letter, nor do I. eapect one. It is my belief that he doesn't want to know the cost per ton-mile and that he doesn't know what is the meaning of the term. He has heard it mentioned and that is all he knows about it. However, I propose to deal with the problem and show why I must have the information for which I asked before I can answer his question.
I have stated that the operating cost of the vehicle is L14 Is. per week, or I3.8d. per mile. If the vehicle be loaded all the time with the four tons mentioned in the letter, then the work done on each mile run is four ton-miles. Four too-miles cost 13.8d., so that the cost per ton-Mile is 3.45d.
Suppose, as is quite likely, that my inquirer, when he
&rites of an average load of four tons, means only four tons on the outward journey; whatever That may be, and that he vehicle returns empty. The weekly-ton-mileage will then oe not 250 times four tians.. but Q Illy 125 (the loaded miletge) times four tons, or 500 ton-miles per week. As the cost 3er week is still 114 Is., the cost per ton-mile is £14 Is. Evicted by 500, which is 6/c1. per ton-mile.
Return Loads Help Now suppose that, in addition to getting a regular load of four tons in one direction, this haulier is able to fill up his vehicle with empty cases, weighing in all, say one ton, on each return trip. In those circumstances his ton-mileage for the outward journey still remains at 500 but is supplemented by a further 125, due to the part loading on the return journey. His total ton-mileage is now, therefore, 625 per week. The total cost remains unaltered and the cost per Ion-mile is reduced to approximately 5.4d., a little under 51d. per ton-mile as against 6id.
That information may or may not be of use to this particular inquirer, I think that his best method of tendering for the work he is offered is to charge per mile run, that is, at 'is. .8d. per mile or, what is practically the same thing, £20 12s. per week.
Let me now return to a problem which I referred to at the conclusion of the previous article. I stated there that it was, a case where it might be possible to make some practical use of the ton-mile as a basis for calculating charges and perhaps also for quoting to the customer.
The problem involved in that inquiry was the cartage of tarmacadam from a central depot to places which might be any distance from one to 10 miles away. The inquirer was using 5-6-ton lorries and wished to quote his customer a price per ton. The difficulty here is that of assessing what is likely to be an average day's work. In my reply I took the average distance of five miles as a basis for calculation although admittedly any result would be only approximate. 1, assumed that the terminal delays at each end for loading and unloading would be 15 minutes, which also assumes that there is no congestion and therefore, no waiting in queues for a load. I took it that the average travelling speed over that five-mile lead would be no more than 12 miles, per hour, on which basis it would be practicable to run six journeys per day, or 30 journeys per five-day week.
Increasing the Economic Price The daily mileage would thus be 60 and the weekly mileage 300. The weekly tonnage would be 150, assuming an average of five tons per load. Now the average charge per week for a 6-tonner, according to the Tables, should be not less than E24. These vehicles, however, are obviously tippers, for which I recommend an addition of 10 per cent.
That brings the weekly charge up to £25 10s. Divide £25 Ws. by 150 and we get the recommended rate: 3s. 5d. per ton. That is not to be taken as being a standard rate for the work, since, as a rule, there is waiting time which considerably reduces the number of journeys which can be completed per day and, in consequence, increases the economic price per ton.
In order to get an idea of the ton-mileage involved, propose to take as examples minimum and maximum distances. Taking the one-mile lead first. I calculate that it will be possible, in the favourable circumstances I have assumed above, to complete 10 journeys per day. The mileage per day will be 20, or 100 per week. The total load carried will be 250 tons per week.
In the case of the 10-miles lead, 1 hour 45 minutes will be necessary for each round journey, so that it is only practicable to reckon on four journeys per day. The weekly mileage will, on that basis, be 400 and the tonnage 100.
Now for the ton-mileage figures. In the case of the one-mile lead the ton-mileage per week is 250 tons, each carried one mile, which is 250 ton-miles. Reckoning that another way: each load of five tons is carried one mile, so that each load accounts for five ton-miles. There are 50 joUrneys per week, which makes the ton-mileage 50 times five, which is 250.
For the 10-mile lead, each load of five tons is carried JO miles, so that the ton-mileage per load is 50, and, as there are 200-journeys per week, the ton-mileage per week is 1,000.
Now the cost per week in the first case is that of a vehicle covering 100 miles per week. According to the Tables, and making the above-mentioned allowance of 10 per cent, for a tipper, the cost is in the neighbourhood of 112 and the charge 120. In the second case, the cost is about 121 and the charge £30.
Over the one-mile lead the charge per ton-mile should be Is. 71d. and over the 10-mile lead a little short of 71d.
If I apply the ordinary methods of assessing a series of rates for varying loads to the above figures for charges per ton-mile, 1 should get a schedule something like the followina:— My argument here that these rates do not mean a thing, either to the customer or the haulier. Surely the customer wants to know what he is going to have to pay per ton of material hauled to the site? The haulier wants to know enough for him to be able to tell the customer just that.
The calculation of the rate per ton is actually easier than the calculation of the tate per ton-mile. Take the one-mile lead. The tonnage haultd per week has already been given. The operator makes 50 journeys per week carrying five tons on each trip. The charge he must make is £20. The rate per ton is thus Is. 73d.
• For the 10-mile lead, the tonnage carried per week is 100, made up of four journeys per day, 20 tons per day and 100 per five-day week. The charge must be £30, and the rate is thus 3s. 73d. A table of rates will be as follows, with a differential, per mile increase in the lead, of a fraction over 23d.
I have a suspicion that this particular inquirer really wanted me to give him an average figure for the cost per ton-mile so that hi could simplify his quotation in that way. That is something I would never recommend a haulier to do when quoting for work of this description. It would only be prattical if he was absolutely sure that the number of journeys would be the same for each different length of lead, and it might not work out right even then,
Suppose I had given him an average rate per tan-mile based on the above calculations. The rate would have been is. lid. Now in a week during which all his journeys bad. been over the one-mile lead his revenue would have been 250 times Is. led., which is £13 16s. against a recornrnalded -Minimum of CM. If he had a week of working over the 10-mile lead his revenue would have been that for I,.,000
ton-miles at Is. which works out at no less than £55 4s.
as against a recommended minimum of 130. '
The same objection applies to the application of an average rate per ton. In the above case the average rate per ton would have been 2s. 63d. In a week of work over the one-mile lead at that rate he would have earned £31 15s, against the correct amount' of 120, but in a week over the 10-mile lead his earnings would have been only 18 2s. 6d, as against 130.
A curiou,s thing to note there is that whereas tIsa'. operator stands to lose on the short leads when he is working to a ton-mile rate and gain over the long leads the reverse is the case when he is working to a rate per ton.
My advice, nevertheless, is still the same. Refuse to quote an average rate. S.T.R.