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HSEHealth & Safety

Executive

Mathematical modelling of the stability of passenger-carrying tandem seat all terrain vehicle (ATV)

Jonathan Webb, MEng CEng MIMechEMIRA Ltd

Watling StreetNuneaton

WarwickshireCV10 0TU

For the first time, passenger carrying tandem all terrain vehicles (ATVs) are being introduced to the UK

market. The Health and Safety Executives (HSE) policy to date has been that passengers must not be

carried on sit-astride ATVs. This policy was formulated when only single seat sit-astride ATVs were

available and needs reviewing now the new vehicles are being marketed. To develop the policy it was

necessary to gain a greater understanding of the stability of these ATVs with passenger carrying

capability. MIRA has been requested by the HSE to conduct a roll-over study on a tandem seat ATV.

The stability assessment conducted involved examining the behaviour of the vehicle in a number of

roll-over scenarios with only a rider on board, and then with both a rider and passenger on board. The

position of the rider and passenger was also adjusted in order to understand their contribution to

vehicle stability during the manoeuvres.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Itscontents, including any opinions and/or conclusions expressed, are those of the authors alone and do

not necessarily reflect HSE policy.

HSE BOOKS

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Crown copyright 2004

First published 2004

ISBN 0 7176 2840 X

All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, or transmitted inany form or by any means (electronic, mechanical,photocopying, recording or otherwise) without the priorwritten permission of the copyright owner.

Applications for reproduction should be made in writing to:Licensing Division, Her Majesty's Stationery Office,St Clements House, 2-16 Colegate, Norwich NR3 1BQor by e-mail to hmsolicensing@cabinet-office.x.gsi.gov.uk

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E1EC2TI3E S2MMARYue to de$elopments in the All Terrain Vehicle (ATV) market, tandem seat ATVs 'ith the capability to carry

passengers are being introduced. /urrent ealth and !afety "#ecuti$e (!") policy ad$ises that passengers should

not be carried on sit&astride ATVs, but this policy 'as based on single seat ATVs only and needs re$ie'ing in light ofthe ne' $ehicles becoming a$ailable. 0ith little information a$ailable on the roll&o$er stability of ATVs 'ith

passenger carrying capabilities, *A has been re+uested by the !" to conduct a roll&o$er study on a Tandem !eat

ATV.

*A pre$iously conducted a roll&o$er analysis for the !" on an ATV for the purpose of assessing the effecti$eness

of a *oll&1$er 2rotection !ystem and the roll&o$er scenarios de$eloped during this e#ercise ha$e been adopted for thisstudy. The programme of 'ork 'as set 'ith these obecti$es3

To create a $ehicle model of the ne' ATV including rider and passenger

To simulate the performance of the ATV in fi$e roll&o$er initiating scenarios

To assess the effect of rider and passenger position on the stability of the $ehicle during the manoeu$res

As a result of the study, the follo'ing recommendations are made3

*iders of the ATV should e#ercise caution 'hen operating the $ehicle 'ith a passenger on board, as the presenceof the passenger reduces the ATV%s stability. o'e$er, 'ith a ma#imum recorded reduction in stability of 44 5,

the increased ha6ard is not considered to be o$ertly high

t should be made clear to both riders and passengers that although their position on the $ehicle has only a small

effect on its stability, at all times they should try and resist the motion of the $ehicle as this 'ill act to increase the

ATV%s stability

The stability of the ATV is most sensiti$e to rider and passenger positioning 'hen it is in$ol$ed in scenarios that

induce side'ards roll&o$er. *iders and passengers should therefore be made a'are that their position on the$ehicle is more important 'hen encountering situations in$ol$ing tra$ersing slopes, dri$ing side'ards o$er an

edge and negotiating bumps

This study only considers lo' speed roll&o$er stability and the results cannot be interpreted to co$er high speed

handling stability or lo' friction surfaces. t is ad$ised that additional tests and analyses are conducted if these

situations are to be considered

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$ ITROD2CTIO

*A has been re+uested by The ealth and !afety "#ecuti$e (!") to conduct a roll&o$er analysis on a ne' All

Terrain Vehicle (ATV). *A pre$iously performed a roll&o$er analysis on an ATV for the purpose of assessing theeffecti$eness of a *oll&1$er 2rotection !ystem. The results of this study 'ere issued in *A report 78&9:9;

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Table ) Scenario , side2ard o0er a b.m/

escription Vehicle dri$en at @Dmph and left side hits bump in road

echanism The $ehicle tends to roll laterally

Test 2rocedure !i6e of the bump is increased in 4 mm increments until roll&o$er occurred

easure *oll rate and angle are monitored. *oll&o$er is determined to ha$e occurred 'hen the roll rate does not e#hibit

a re$ersal through deg-s

Table + Scenario 4, for2ard do2n a slo/e

escription Vehicle dri$en do'n a slope at

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Table / Meas.red ATV /ro/erties/entre of gra$ity position nertia

/ondition ass (kg) E (mm) (mm) G (mm) ## (kgmm@) yy (kgmm

@) 66 (kgmm

@)

Kerb

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Table 7 sho's the effect on the corner 'eights of the rider on board and leaning. *esults are gi$en for

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Table 44 sho's the effect on the corner 'eights of the $ehicle 'ith rider and passenger on board, but 'ith ust the

rider leaning. *esults are gi$en for the rider 'ith a

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Table $) Sim.lation res.lts for scenario (

Configuration Slope angle at which roll-over occurred (deg)

*ider only @9

*ider resist @D

*ider and passenger @