A brake activation system for reducing the time between the brake application of tractors and trailers utilizes a speed differential between the electrical and air signals. The application of the tractor brake actuates simultaneously a stop light circuit and the air brake systems. The electrical signals from this energized stop light circuit actuates solenoid valve which releases the air from the trailer reservoir being subsequently reduced to a predetermined low pressure level. This low pressure air reaches the trailer wheel brake chambers prior to the arrival of the brake air with high pressure overriding the low pressure air route and completing the trailer brake application.
