Interpretation ID: aiam2679
Senior Supervising Engineer
Oshkosh Truck Corporation
Box 2566
Oshkosh
WI 54901;
Dear Mr. Nimmer: This is in reply to your letter of August 29, 1977, asking fo confirmation of your interpretation of S4.5.4 of Motor Vehicle Safety Standard No. 108.; Paragraph S4.5.4 requires that 'The stop lamps on each vehicle shall b activated upon application of the service brakes.' Oshkosh trucks are equipped with split air brake systems. This system incorporates a parking brake system on the rear axles. You indicated that there are three conditions under which the parking brakes will apply:>>>; Condition 1. - Parking Application. The spring brakes are driver applied through a hand operated parkin control.; Condition 2. - Rear Service Brake System Failure. The spring brakes can be driver applied through the service brake foo operated treadle valve control in the event of a failure in the rear service brake system.; Condition 3. - Spring Brake Cavity Pressure Loss. A component failure which allows air pressure to exhaust from th spring cavity of the rear brake chambers will cause the spring brakes (parking brakes) to apply. This condition is not driver initiated.'<<<; You have interpreted Condition 2 as the only 'services brake application since it is the only one of the three that is driver-initiated through the service brake control, and that stop lamp activation under the other two Conditions is not required by Standard No. 108.; This will confirm your interpretation. With respect to Condition 1, w do not consider that driver application of the parking brake portion of the service brake system is 'application of the service brakes' within the meaning of S4.5.4. Nor do we consider that activation of the parking brakes through component failure is 'application of the service brakes', your Condition 3.; Sincerely, Frank Berndt, Deputy Chief Counsel