More About the "Ton-mile"
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Differences Between this Factor as Applied to Assessing Vehicle Performance and its Occasional Value in Calculating Operating Charges : How Empty Running and the Use of Different Sized' Lorries Affect Computation
IN my previous article 1 showed, by reference to a number of haulage operations, how seldom was it necessary to use the ton-mile. I concluded by defining the ton-mile: I begin this one by giving a broader interpretation of the term.
For the better handling of the subject, I am going to suppose that I am writing an article on academic lines, in that way I must begin by pointing out that there arc two ways in which the term is commonly interpreted. There is .what I call the academic one wherein the total weight of the vehicle plus the weight of its load, the weight of ihe driver (and mate too, if there is one), the fuel and anything that is being carried must be taken into consideration.
Total Weight for Running In the case of the 6-ton vehicle to which I referred in my previous notes, its unladen weight is taken to be 3 -tons, the payload 6 tons, a driver and mate 2i cwt., and sundry extras weighing another I i cwt. The total weight for calculating ton-mileage is 9 tons 4 cwt. That is the way in which the Royal Automobile Club and other bodies calculate ton-mileage when they are ascertaining the performance capabilities of heavy vehicles, bearing in mind that one of the matters for judgment is the efficiency of the engine.
In like circumstances, the haulier is concerned with only the 6 tons of payload, and, whereas, calculating according to the academic method, the ton-mileage relating to a run of 10 miles would be 10 times 9.2 tons, which is 92 ton-miles, the figure for the haulier would be 10 times 6 tons, i.e. 60 ton-miles. As this article is directed only to practical men, a prolonged discussion of the former method is unnecessary and, save for academic purposes, I mention it solely to acknowledge its existence and to avoid misapprehension on the part of those readers who arc not haulage contractors. They are sometimes inclined to be carpingly critical and, if I had not dealt with the academic method, would quite likely challenge not only my interpretation of the meaning of the term but my knowledge of the subject.
The definition still remains unaffected whether we are interested in the practical aspect of' the matter or the academic one. It is., still weight hauled stated as tons, Multiplied by the distance the load or the weight is carried.
Guide to Performance Here I must ensure that I have not stressed the academic aspect and given the impression that it is of small importance. I must explain that there are various ways in which what I have called the academic ton-mile can be put to practical use. One of these ways is applied in nearly every issue of The Commercial Motor: it appears and serves a most excellent purpose in those articles written by L. I. Cotton when he describes the performanceof new models.
Take as an example the road test of the Bristol-E.C.W. eight-wheeler, published in May 22 issue. The weights arc given as: unladen weight, 7 tons 10 cwt. 2 qr.; payload, 14 tons 7 cwt. 3 qr.; driver, observer, etc., 3 cwt. 2 qr. The total is 22 tons 1 cwt. 3 qr. For convenience in making the calculation which follow, that total is expressed as 22.1 tons.
The fuel consumption during one part of the test, when the conditions were those to be expected if the vehicle were engaged on trunk service, was given as 12.4 m.p.g. at a speed of 21.5 m.p.h. (average). The ton-mileage, calculated from the above figures, was shown to be 274 gross ton-m.p.g.
B28 The calculation by which that figure was reached was simply to multiply the gross weight, 22.1 tons, by 12.4, the distance run while making the test.
With those figures before him, the reader can make comparisons and ascertain from them which vehicle is the most economical as regards expenditure on fuel. The knowledgeable user, whilst appreciating that this method is the only way in which a proper comparison can be made, will subsequently want to know what is the consumption in miles per gallon, taking into consideration only the payload figures. In this case, for example, the payload is 14 tons 7 cwt. 3 qr., which, in decimal form, is approximately 14.4 tons. The m.p.g. is unaltered at 12.4 m.p.g. That figure will satisfy him: he will rarely wish to know the payload ton-mileage per gallon.
In my previous article I referred briefly to a man who had purchased two 1-ton vans. I gathered from his letter that he had bought the machines so that he could enter into a contract. The work was fairly regular. Each vehicle• would, according to the terms of the contract, be running 250 miles per week, with no extras. I judged, reading between the lines of this letter, that the vehicles would be loaded to capacity either one way or two ways, there being no reference to part loads or to any programme of work which involved " drops " or " pick-ups" along the route to be followed.
Need Extra Information The inquirer asked me to give him a figure for payment per ton-mile. In reply I told him that if I must calculate the ton-mileage I must have some additional information. I should want to know what was the percentage of the travelling time the lorry would be loaded and what loads would be carried during that time. I have received no answer to my 'letter. In my letter asking for information I advised him that his operating cost per mile would be about is. 3d., and that his minimum charge should bring him in a revenue per week. of E25, or 2s. per mile run. At that rate the allowance for gross profit would be £9 7s, 6d.
The fact that he did not reply to my letter yet at the same time accepted my recommendation as regards his charge per mile confirmed my opinion that he did not know what was meant by the term ton-mile, and would not know what to do with the information if he got it. I will now deal with his inquiry as if he really needed the information.
I have shown that the cost of operating each of his vehicles worked out at Is. 3d. per mile, running 250 miles per week. The ton-mileage is that of 1 ton carried 250 miles, that is to say, the weekly ton-mileage. is the same as the weekly mileage. The charge on either basis must be the same as the cost is Is. 3d. per mile and the cost per ton-mile is also Is. 3d.
One-way Loading It may be. however, that the lorry is loaded one way only, returning empty. There is nothing in the letter to say. If it is one-way loaded, then the ton-mileage is 125 and the cost per ton-mile is 2s. 6d.
• Now suppose that, in addition to getting a regular load one way, this haulier is als!e to fill up his vehicle with empty cases, weighing in all 4 cwt., or ton, on the return run. In those circumstances his ton-mileage is 125 on the out wards journey and ton multiplied by 125, which is 25 ton-miles, on the return. The total for the double journey is thus 150 ton-miles. The cost per mile still stays at Is. 3d. and the cost per round trip of 250 miles is £15 12s. 6d. and the cost per ton-Mile is 2s. rd. I arrive at that figure by dividing the figure for the total ton-mileage, 1,50, into the total cost per trip, £15 12s. 6d.
That information may or may not be of some use to the inquirer. Personally I do not think it will be any use at all. I think the best method of tendering for the use of a 1-tonner involving 250 miles per week is to charge a definite figure of 2s. per mile or £25 per week.
Here is another problem in which there may be some useful purpose served by quoting on a ton-mileage basis. It relates to the cartage of Tarmac from a central depot to places which might be any distance between 1-10 miles. The inquirer was using 4-ton lorries and 2-tonners. He wanted information which would help him to quote per ton. The difficulty here is the fairly obvious one that it is hard to assess an average day's work.
In my reply I took the average distance of 5 miles as a fair basis for that average, although I admitted that it was little more than a guess. I assumed that the terminal delays were 15 minutes each for loading and unloading. The average speed of travel, nearly all of the journey being through congested traffic areas, I took as 16 m.p.h. On that basis it was possible to make eight complete journeys per day, 44 hours per week allowed for 44 journeys. The tonnage carried would be 176 on the 4-tonner but only 88 on the 2-tonners.
The charges I then calculated using the time and mileage figures from the current issue of "The Commercial Motor Tables of Operating Costs." For the 4-tonner the data were 6s. per hour and 10d. per mile: for the 2-tonner 5s. 6d. and 91d. respectively.
Minimum Earnings
Taking first the 2-tanner. The weekly mileage was 440 and the time 44 hours. For 440 miles the charge, at 9id. per mile, works out at £17 8s. 4d.; for the time, 44 hours at 5s. 6d. per hour, the charge must be £12 2s. For the week's work the operator should get a minimum of £29 10s. (omitting pence).
For the 4-tonner the time charge must be not less than £13 4s., and for mileage £19 14s. Total, £32 18s. For that amount the tonnage carried was 176, so that the charge per ton when using the 4-tanner was 3s. 9d. On the 2-tanner only 88 tons are carried for a charge of £29 10s.; that is equivalent to 6s. 8d. per ton.
That comprises all the information I gave to this inquiry, leaving it to the haulier to decide by striking an average between the two, taking into account the number of 4-ton and 2-ton loads he was going to be able to take. In order to get some figures for ton-mile age I propose first of all to take as examples the maximum and minimum figures.
The minimum distance is one mile and I think we may reasonably take it that the numbers of journeys will be 11 per day. The total mileage per week of each of the two vehicles will be ill. The charge must be, for time, the same as before, namely £12 2s. for the 2-tanner; for the 4-tanner £13 4s. For the mileage charge we must take, for the 2-tonner, Ill times 90., which is £4 8s.; for the 4-tonner, 111 times 101d., which is £5 to the nearest shilling.
The total charge per week must therefore be £16 10s. for the small vehicle and £18 4s. for the larger one.
Four Trips a Day
In the case of the maximum distance, 10 miles, 1 hr. 45 min. will be necessary for each journey out and home, which means that only four trips per day or 22 per week will be possible. The daily mileage will be 80 for each vehicle. The tonnage on the 4-tonner will he 16 per day or 88 per week: on the 2-tonner the total will be 44 tons per week.
As regards the use of the ton-mileage figure, ihis can usefully be calculated. The tonnage on the 4-tonner has been shown to be 16 per day on the maximum mileage: that is 160 ton-miles (16 tons by 10 miles). On the 2-tonner these figures must be halved.
Considering the 4-ton vehicle only and taking the figure of 3s. 9d. per ton as calculated above for the average 5-mile lead, the revenue from the one-mile trips would be £8 5s. per day which, for 22 miles is equivalent to 8s. per mile run. In the case of the 10-mile trips, the revenue is only 16 times 3s. 9d. which is £3, equivalent to only 9d. per mile. Obviously that will not do and, if the average figures are to be maintained the only hope is that what is last on the long-distance trips will be made up on the short-distance journeys.
When I calculated the average figure of 3s. 9d. per ton. I reckoned that it was possible to do eight trips per day, each trip of 5 miles out and 5 miles home. The ton-mileage in this case would be 160 per day and the tonnage 32. In this instance, 3s. 9d. per ton is equivalent to a revenue of £6 per day. If we divide that by the 160 ton-miles we find that the rate per ton-mile is actually 9d. If the haulier is paid per ton-mile at the rate of 9d., then his revenue when he is doing the one-mile trip with the 4-tanner will be £6 per day instead of £18 4s. per week. S.T.R.