Why do traffic police uniforms "glow"

The luminous part of the traffic police uniform includes the words on the belt and clothes. The band emits fluorescent substances, also known as luminescent substances, rather than reflective substances. Its luminous principle is that when there is light, the substance is excited by light and becomes an unstable excited state, while when there is no light, the excited state substance will return to the ground state and release energy in the form of optical radiation. Fluorescent substances are characterized by a long lifetime of excited States, that is, a long light decay period, so they can last for a long time. There are also some cases where slow chemical reactions are used to emit light. The traffic police usually take the first one. The words on clothes are reflective parts made of special materials.