Investigation Into O2 Trailer Brake Requirements

Report Number: MIRA-0235082-001-01

A fatal accident involving an O2 trailer occurred in September 2003. The accident happened because of modifications that had been made to the trailer’s auto-reverse parking brake mechanism. Although the modified trailer met C&U requirements, the parking brake would not prevent trailer movement if it were subjected to a side force. The Department for Transport asked MIRA to review the current C&U and type approval braking requirements for this type of trailer and whether type approval tests need to be extended to overcome this potential problem on O2 trailers.

The fault was reproduced under test conditions and it was found that the trailer could become unstable when on a certain gradient without the application of any external disturbing force. An investigation was undertaken to establish whether a simple test could be devised to establish whether the trailer braking system compensator functions correctly.

The following conclusions can be drawn from the work described in the report:

• Although there is no requirement in the UK to do so, the trailer industry tends to use components from established brake suppliers whose brake system components have already been type approved. Hence a change in the type approval requirements would have a direct influence on the components used by trailer manufacturers.
• The proposed test procedure defined in this report has been shown to be capable of detecting whether the compensator design is effective in coping with differential brake torques
• EC Directive 71/320/EEC Annex VIII (which deals with calculations for the forces and travels within the brake system) can be amended to cater for the situation when one brake goes into reverse torque mode
• The type approved system fitted to the test trailer failed to achieve the minimum requirement of holding the trailer on an 18% gradient, even with a straight compensator fitted. The test work has shown that satisfactory system installation is essential for correct operation of the brake system.

It was concluded that if appropriate changes were made to the EC Braking Directive that the problem would be addressed for new trailer designs.

HGV Trailer Braking Compliance Report

Report Number: MIRA-04-235082-01

Unlike most countries in Europe, in Great Britain heavy goods trailers are not subject to any form of type approval inspection prior to use on the road. The trailers braking systems need to meet the relevant legislation in the Road Vehicles (Construction & Use) Regulations. Instead of trailer type approval, manufacturers submit brake performance data for their products to the Vehicle and Operator Services Agency (VOSA) Technical Services. This data is evaluated by experienced staff, who then decide whether the trailer is either approved or rejected.

The Department for Transport was concerned, however, that some HGV trailer braking systems do not comply with the information provided by the manufacturer. There was anecdotal evidence that the data provided is inaccurate or vehicles may not be able to achieve the performance indicated during normal (dynamic) road use. Failure to achieve the prescribed performance requirements could compromise road safety.

The purpose of this research project was to investigate the issues involved by:

• Studying current practice in Great Britain and other countries
• Assessing the effectiveness of current procedures
• Inspecting 12 HGV trailers for build compliance against supplied data
• Subjecting each trailer to a full type approval test to EC/ECE requirements
• Performing the same test and initial inspection process as undertaken by VOSA
• Providing advice on possible solutions, including new or revised assessment and inspection procedures.

The report contains a detailed description of the findings of the investigation and includes recommendations for changes to the current process.

Final Report for Risk of Injury Through Using
Additional Cushions on Car Seats

Report Number: MIRA-1003840-001c

Current car seat design is based on safety, comfort and functionality. It has been recognised from previous research projects that people of short stature may find it difficult to reach primary controls in a vehicle or obtain an adequate view for driving.

Previous research has highlighted that there is likely to be an increased risk of injury to the driver during a crash whilst using these devices. As a result, the Department for Transport’s Mobility and Inclusion Unit has commissioned research to investigate this theory further.

This project investigates the likely increase in risk of driver injury, caused by the inclusion of additional cushions in vehicle seats.

Drivers' Perception of Secondary Braking

Report Number: MIRA-03-0235036

It has been reported to the DfT that in accidents where vehicles have suffered "brake failure", drivers may not be making full use of the secondary braking system, believing that their vehicle's brakes have completely failed. The result is that the vehicle may be involved in a collision that could have been avoided.

The purpose of this research was to determine the current situation and to develop proposals to improve road safety by proposing changes in vehicle braking legislative requirements and/or increasing drivers' knowledge and understanding of the vehicle's braking system.

Occupant Behaviour During Pre-Impact Braking

(Car Passengers)
Report Number: MIRA-0415024

The PRISM project seeks to identify suitable smart restraint requirements for Europe This report on task 1.5 is to determine front seat passengers behaviour during pre-impact scenarios to identify likely postures at the start of an impact event.

A total of 49 volunteers, 4 MIRA project staff and 6 crash test ATDs undertook a range of tests, totalling 230 in number. The tests were undertaken in an instrumented test vehicle, also fitted with 5 video cameras.

These results are discussed and conclusions drawn. Recommendations are made to assist in the future work packages of the PRISM project.