This paper reviews psychophysiological measurement applied on humans, by mainly focusing on brain waves observed by EEG sensor placed on scalp during brake performance testing. During braking high physiological stress, response and fear are observed, hence brain waves are monitored during brake test. Brake performance by two drivers (i.e. Driver A & Driver B) significantly established the difference in brain potential between driver A &B. During the test, brake performance parameters such as vehicle speed, deceleration rate, brake force, stopping distance are also measured. Observed EEG signal during the braking event, revealed the difference in emotional status of two different drivers. Signal based on alpha and beta from brainwaves were evident to define the mental stability of the respective driver.