An improved method of assessing the catalyst warm-up rate of a motor vehicle catalytic converter is based on the response rates of fast warm-up exhaust gas sensors located in the exhaust gas upstream and downstream of the catalytic converter. For example, the brim of the hat may be illuminated in its entirety in a particular color and the sole of the shoe may be illuminated in a complementary color such that a person wearing the cap and shoe of the invention in low light situations may be readily visible. Between signals to drive the actuator, an output time of a deceleration signal is set to a predetermined ratio of a time during which an acceleration signal is outputted. Physical layer attributes can include: state-of-polarization changes, changes in polarization-mode-dispersion, change in propagation delay, changes or loss-of-light, changes in OSNR, changes in BER between the two nodes.