The Technical Editor examines the latest weights and dimensions proposals
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being 30 tons if the axles are 29 ft. 6 in. apart, 28 tons if they are 26 ft. apart, 26 tons if 23 ft. apart, and 24 tons if less than 23 ft. apart. This is all in the interests of preventing damage to road bridges, so the official story goes. yet I have spoken unofficially to Ministry men who claim that most bridges in this c,puntry will stand 13-ton axles. Through all these weight changes for artics, the lorry-and-trailer combination sails on unscathed, there being no intended change • in its gross weight from the present figure of 32 tons.
If the object of limiting articulated vehicles to 42 ft. 7.75 in; overall length is . manceuvrability, why should rigid eightwheelers with turning circles of over 100 ft. be suggested? Surely larger artics could be allowed? Even the 14 m. (approx. 46 ft.) dimension common on the Continent would be an improvement. And if manoeuvrability is so important, why no turning-circle limits? One might, in fact, go the whole hog and introduce an overall-height limit also.
There is no doubt in my mind. that the heavy artic will come out on top if these new regulations are adopted, however. Quite apart from anything else, it wilt be easier for vehicle makers to produce tractive units to fit the proposed limits than_ to design long rigids, whilst many trailer companies already build semitrailers for export which would meet the new proposals. The longer semi-trailers would be allowed to operate with existing tractive units, although not at higher gross train weights than are at • present permitted, of course, and this would at least allow operators to make gradual change-overs to the new dimensions, which might be a help.
Linked with Plating One of the things that pleases me most abodt these latest proposals is the talk of introducing " plating " regulations for new vehicles, particularly as these could well be in force before the London Commercial Motor Show in September. These proposals alone should help to stop commission-happy car salesmen selling completely inadequate light commercial vehicles to operators who should know better in the first place, whilst it will also give a fair crack of the whip to the true heavy-vehicle manufacturers who have had to watch the market for their lighter models eaten into by the mass-producers.
Even better to come; I understand it is possible that the original plan for a comprehensive system of plating for all commercial vehicle--both old and new could well be put into effect by about the end of next year, and this can be expected to incorporate a form of minimum powerto-weight ratio, and so in this respect alone could cut across the present proposals, whatever they might be. Not that a straight power-to-weight ratio specification is the answer really, for much
depends on how, the power is used: it is really the tractive effort at the rear wheels which decides how slow or otherwise a heavy goods vehicle is going to be, 'as has already been realized in Italy.
Whatever happens, though, it looks as though Mr. Marples' merry men are determined to get to grips with the problems of overloading and underpowering, and who an seriously claim that this is a move in the wrong direction?
Braking Standards Another most satisfactory proposal is that (unfortunately only. "new") heavy vehicles will be subject to the braking requirements already laid down for private cars and goods vehicles of up to 1.5 tons unladen in schedule 4 of the 1963 Motor Vehicles (Construction and Use) Regulations. The Ministry says that .these braking requirements will not have to be complied with by existing vehicles because the weight limits of existing vehicles are not to be raised, which leads me to suppose that somebody in the Ministry is not dissatisfied with the present braking standards. Perhaps this man has never driven a heavy vehicle lately! Schedule 4, in so many words, implies that footbrak.e efficiency should be no less than 50 per cent and handbrake efficiency no less than 25 per cent.
Well, I suppose this is something, although presumably these efficiency figures will be measured by some form of meter which actually records maximum effiCiency only. It would be far better—particularly for new vehicles—if an efficiency based on actual stopping distances were to be employed, and a footbrake efficiency of 50 per cent measured in this way is equivalent to an actual stopping distance of 60 ft. from 30 m.p.h.—and 167 ft. from 50 M.p.h.! A meter reading of 50 per cent could mean anything; it all depends on the type of Meter, whereabouts on the vehicle it is placed, and how the brakes are applied. I am surprised, also, that no reference has been made at this stage to the. provision of a form of auxiliary braking in addition to that offered by the handbrake, or at least some minimum braking size per ton of gross vehicle weight which might help to give safer conditions at unlimited speeds on motorways.
All in all, however, the new proposals are certainly not to be condemned outright, especially as they show promise of even better things.They are not going to he popular with many hauliers (although C-licencees should be less affected), but they have obviously been drawn up by people fairly well acquainted with the British haulage industry, and perhaps with a little less prejudice they would have been almost perfect.
JOHN F. MOON.
A.M.I.R.T.E.
C,