The performance of lorries which are heavier than currently permitted in the UK was compared with that of lorries conforming to the present limits. The sample of vehicles tested was too small to be the basis of firm conclusions. The tests showed that the overall stopping performance of many of the heavier vehicles, both laden and unladen, was inferior to that of existing 32.5 tonne vehicles but that the braking stability of the higher gross weight combinations was no worse than that of the 32.5 tonne vehicles. There was a tendency to jack-knife under some conditions but less instability was experienced with 3 axled tractive units than with 2 axled tractive units. Heavier vehicles were progressively less resistant to overturning - this progression can be halted briefly by the addition of a third semi-trailer axle at any given gross weight. The heavier vehicle combinations were no more difficult to drive and handle than the 32.5 tonne vehicles. The emission of noise and smoke from heavier vehicles need be no greater (and can be less) than from current 32.5 tonne vehicles. With certain of the vehicles it would not have been possible to keep to the current UK limit on length of 15 metres. The vehicles tested were longer than 15 metres, but this did not affect their handling characteristics. With some of the heavier combinations it was necessary to arrange a load distribution which was far from uniform in order to achieve maximum gross weight without overloading at least one axle. Taking into account both track tests and analytical studies it would appear that, in fuel used per payload tonne kilometre, there is a potential small saving in some cases and not in others through the use of vehicles heavier than are permitted by the current UK 32.5 tonne limit. /TRRL/

  • Corporate Authors:

    Department for Transport, England

    Vehicle Standards and Engineering Division, 2 Marsham Street
    London,   England  SW1P 3EB
  • Authors:
    • Chatfield, A G
    • KEMP, R N
  • Publication Date: 1979-1

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 15 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00195168
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Report/Paper Numbers: Report VSE 514 Monograph
  • Files: ITRD, TRIS
  • Created Date: Aug 15 1979 12:00AM