This paper gives the main reasons for the occurrence of overturning incidents with articulated vehicles. It contains details of a simple theoretical analysis of the problem, the results of which can be used to give an approximate value of the overturning limit for a given vehicle, from a relatively limited amount of information on it. Details and results of tilt table tests on various representative vehicles up to 44 Ton Gross Train Weight are included along with a limited amount of information on dynamic roll measurements. A computer programme devised to take into account all the stiffnesses, weights and dimensions of a vehicle in the calculation of its cornering limitations is explained and examples are given which show the relationship between the results for the various methods of estimation used. The computer programme is used to determine the effect of varying the fifth wheel roll stiffness, trailer suspension stiffness, trailer torsional stiffness, tractor suspension stiffness, trailer centre of gravity height and longitudinal position in order to establish the relative importance of these in relation to the vehicle stability. It is concluded that the basic problem of articulated vehicle roll-over stems from the simple fact that the overturning speeds of average vehicles negotiating frequently experienced curve radii are remarkably low, for instance 6.7 m/s round a 18.3 m radius bend produces a lateral acceleration of 0.24 g, quite sufficient to cause a vehicle with a 2.74 m high trailer centre of gravity to overturn. The parameter study clearly indicated that the most important single parameter to be controlled is the trailer centre of gravity height, which should be kept as low as possible. Since in many cases it will be impracticable to lower the trailer centre of gravity or make any appreciable improvement in the roll-over stability of the vehicle, a campaign of driver education might serve to make those most intimately concerned with the problem more appreciative of the low limits involved for safe cornering. A long term solution to the problem may be found in the modification of various troublesome portions of road by easing the radii which the vehicles have to negotiate; in many cases this could be effected by the reduction of the island diameter on particularly tight roundabouts.

Media Info

  • Pagination: p. 91-107

Subject/Index Terms

Filing Info

  • Accession Number: 00262740
  • Record Type: Publication
  • Source Agency: Highway Safety Research Institute
  • Report/Paper Numbers: C203/73
  • Files: TRIS
  • Created Date: Dec 13 1974 12:00AM