[Code of Federal Regulations]
[Title 49, Volume 6]
[Revised as of October 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR570.54]

[Page 198]
 
                        TITLE 49--TRANSPORTATION
 
                   CHAPTER V--NATIONAL HIGHWAY TRAFFIC
                    SAFETY ADMINISTRATION, DEPARTMENT
                            OF TRANSPORTATION
 
PART 570_VEHICLE IN USE INSPECTION STANDARDS--Table of Contents
 
         Subpart B_Vehicles With GVWR of More Than 10,000 Pounds
 
Sec.  570.54  Definitions.

    Unless otherwise indicated, all terms used in this part that are 
defined in part 571 of this chapter, Motor Vehicle Safety Standards, are 
used as defined in that part.
    Air-over-hydraulic brake subsystem means a subsystem of the air 
brake that uses compressed air to transmit a force from the driver 
control to a hydraulic brake system to actuate the service brakes.
    Electric brake system means a system that uses electric current to 
actuate the service brake.
    Vacuum brake system means a system that uses a vacuum and 
atmospheric pressure for transmitting a force from the driver control to 
the service brake, but does not include a system that uses vacuum only 
to assist the driver in applying muscular force to hydraulic or 
mechanical components.