By the sound of it Pronto this is something that someone might be tempted to wear in the cockpit, which would not be a good idea.
The whole point of these jackets is that they are reflective and reflections on the inside of the windshield are exactly what you don't want.
If you do have to wear one it should be stowed when driving (aeroplane or car) which is I suspect why the traffic police put them on when they get out of the car rather than wearing them while driving.
On a lighthearted note I heard of a way in which they can cause accidents.
A friend works for the Vehicle Inspectorate and gets called out to investigate accidents. A truck had lost a wheel but was safely on the hard shoulder with a police car behind and traffic flowing freely past.
My friend stands in front of the truck in his fluorescent jacket to take a picture. Passing motorist sees someone yellow pointing a device in his direction, assumes it is a speed gun and james the brakes on. Multiple pile-up as several cars run into each other.
Exit friend, leaving police to sort out the mess.
Haven't seen the picture yet but I gather it has nicely captured the smoke emanating from the tyres.
Mike