Item 21 (Limiting cases for the usage of certified characteristic values) (R55-04­­-11, R55-05-05, R55-06-09, R55-07-06, R55-07-14, R55-08-03, R55-08-04, R55-08-05, R55-09-04, R55-09-05, R55-09-11, R55-09- 13, R55-10-03: R55-10-04; R55-10-05; R55-10-06; R55-10-07; R55-10-08; R55-10-15)
At the previous meeting Mr. Stokreef requested more of the background information to the ISO18868:2013 standard. In order to respond to that request Mr. Svensson had uploaded the documents R55-10-03: R55-10-04; R55-10-05; R55-10-06. The last of those documents was a history summary over the work with that standard going back to 2002. The document R55-10-07 was a summary of many recent measurements of coupling forces in different vehicle combinations. There is also a comparison with the requirements as calculated using the ISO18868:2013. It could be noted that the measure peak forces only at on instance came close to the fatigue test load corresponding to the performance required.

Mr. Westphäling at the 9th meeting argued that road conditions in Germany are worse than in Australia. To this meeting Mr. Svensson had gathered information that showed that the German Autobahn does not have worse conditions than the Australian roads. Hence the measured forces and the experience over 30 years supporting the ISO18868 are valid. Mr. Stokreef was not present but had prior to the meeting expressed support for the proposal for this item. Mr. Westphäling argued that different engine power and and brakes requirements would the still make the proposal questionable. In response to that Mr. Svensson showed the diagram in the document R55-10-07. There it could be seen that the real high coupling forces is generated neither by traction nor by braking but through interaction between unevenness in the road and the geometric layout of the vehicle combination. Hence the difference in engine power and braking performance is not a significant factor. While support for the proposal is converging Mr. Westphäling wanted to the next meeting to challenge OEM:s and trailer manufactures for more measurements. Mr. Alguëra was doubtful whether there are any better measurements available. Next meeting