However, I realise the slight lack of functionality when it comes to sudden downpour while we are donning the safety vest.
Should it rain suddenly, we will be caught unprepared and drenched. Carry and use of umbrella sometimes inhibit what we can do as compared to when we are operating handsfree.
So I have customised a rain jacket with safety vest (sleeves removable). The initial thought was to allow me to be prepared at all times, so my first aid and other EDC items are on the safety vest side even when I'm wearing it as a jacket.

Should the need arises, I can wear the flipside and be ready to render assistance to injured persons.
Currently it is on trial and with Singapore's weather in mind, I hope to improve it further with the help of other individuals who are looking into your personal safety and yet functionality for your Every Day Wear / Every Day Gear.