Interpretation ID: aiam1514
Vice President
Marketing
The Berg Manufacturing Company
333 East Touhy Ave.
Des Plaines
IL 60018;
Dear Mr. Campanini: This responds to your December 21, 1973, letter and subsequen communication with Mr. Sidney Williams of the NHTSA Handling and Stability Division asking if a check valve located at the isolated reservoir (as pictured in your schematic drawing) to protect the trailer service reservoir(s) would comply with S5.2.1.5 of Standard No. 121, *Air brake systems*.; The check valve may be placed at the isolated tank to protect th trailer service reservoir as specified in S5.2.1.5.; It appears from your schematic that a single failure in the servic brake system could cause loss of service brakes on both trailer axles. It should be noted that if this arrangement is used and a significant safety problem results, it would be subject to NHTSA safety defect authority.; Yours truly, Richard B. Dyson, Assistant Chief Counsel