The scope and purpose of the SAE Recommended Practice is to provide standards for the control and indication of parking brakes in hydraulic braked vehicles over 4540 kg (10 000 lb) GVWR. This recommended practice pertains to automatic transmission applications and supplements the SAE J915 recommended practice. This recommended practice does not address parking brake system performance. Parking brake system performance, both static and dynamic conditions, is the responsibility of the OEM vehicle manufacturer or manufacturers that modify the vehicle by adding special vocational required equipment (such as but not limited to outriggers, cranes, etc.).
There are several parking brake indication and control philosophies for hydraulic braked vehicles with a GVWR greater than 4540 kg (10 000 lb). For future vehicle and parking brake system designs, this recommended practice is intended to be a guide for consideration. The implementation of this new recommended practice will reduce operator confusion and promote standardization in all hydraulic braked vehicles. This recommended practice is intended to supplement the SAE J915 Automatic Transmissions - Manual Control Sequence recommended practice as it relates to the various parking brake indication options.
Major vehicle manufacturers were surveyed and current practices were identified to assist in the development of this document. Where necessary or possible all current practices were included in this document to allow for alternative methods to provide the specific functions.
The task force recognized that both the “P” and “PB” indication options existed in current vehicle applications. The team evaluated the benefits and risks of both approaches and the following is a summary of the results. In conclusion it was decided to recommend the “PB” indication as the standard method.