Feedback from Mr. Adam (Wabco) as pilot for Annex 21 amendments:

• Collection of data about existing systems
• Mr. Adam did not receive any report or information about ESC in MVCs.
• Possible draft amendments to Annex 21
  • Need to add provision that a towing trailer shall be able to activate the brakes of the succeeding trailer (provision inspired from the tractor provisions).
  • There was a description of the ESC functioning.
  • The experts agreed that adding a dolly makes no particular technical challenge with regard to ESC functioning and development. Yet the concern stays with the non-EBS trailers when they are part of a MVC.
  • The idea of using the pneumatic characteristics of the suspension was discussed (this system does exist on hydro/pneumatic systems for agriculture vehicles), but rejected because
    • The dynamic reactions of the suspensions are not fast enough
    • The air suspension is designed as a levelling system (one sensor for six wheels).
  • ISO11992 does contain EBS dedicated messages (e.g. EBS21) for data transmission about behaviour of the different vehicles.
  • In view of the above, and in view of the adopted definition of a dolly, the group wondered the necessity of mandating ESC on dollies: risk of creating jack-knifing situations vs. increase of EVSC capabilities
    • As a towing trailer, the dolly must have EVSC
    • The added cost is of low level (if the base system is an electronic braking system)
    • Prevention of jack-knifing relies then on the proper EVSC adjustment.
    • EVSC cannot go beyond the limits of the physics: still need that the vehicles are stable by design.
    • May happen that the vehicle tows an empty dolly: need for communication between the dolly and the tractor.
• Assessment of driver’s acceptability to low lateral acceleration thresholds
  • Activating the stability system earlier than current practice would not be accepted by the drivers. The concern also is related to the driver’s education; the drivers should be aware that they cannot feel when the trailer starts rolling.
  • The Chair informed about discussions in S to increase the height of the vehicles to about 4,50 m. Industry in S voices that this can be done since the vehicles are equipped with EVSC.
  • Mr. Adam proposed that a requirement be added such that a towing trailer should be capable of braking the succeeding trailer. Also changing the settings parameters such that the centre of gravity is higher. On trucks, the axle load sensors (when existing) can evaluate the load, hence make an rough assessment of the possible centre of gravity height, as the load is always added above the unladen centre of gravity.
  • A debate took place on the necessity that the signals are transferred along the whole combination, yet with no mandatory technical solutions. UN R13 currently does not mention “routers”, yet they are permitted at national level. However the point is that the signals are transmitted with no delay. The ISO standard does implicitly foresee the transmission of messages via the input/output requirements.

Conclusion:

• Group to define the necessary messages/information that need to be transferred back and forward
• Addition of a requirement that a towing trailer must have the capability of transmitting the message/information defined above.