Cut here?

[Dave Mann]

I've noticed that many HGV road tankers have a line of dashes round the periphery of the tank end, what re they for?
Is it to indicate where to cut?    

[JohnD]

They are Conspicuity Markings

A blurb from the web:

From July 2011, all newly registered HGVs over 7.5 tonnes and trailers over 3.5 tonnes must have reflective conspicuity markings that clearly outline the rear and sides of the vehicle to make it visible for up to 1000 metres at night. ECE104 specifies the standard for the reflective materials used, and where an how it must be positioned on the vehicle or trailer.

Assume its more efficent to use straight tape as a hatched line aroun the curve than cut a circle from a big sheet

You will also now notice, yellow stripes down the side of vans used on the highways by councils, and road maintinence who stop often

[Dave Mann]

I live and learn, thank you JohnD, although I doubt they will be visible for 1000 meters.

[andrew34ruby]

When only a few trucks had these reflectors around the edges of box vans I noticed that they were much easier to see at night on unlit roads. I'm thinking of maybe 35 years ago. A thousand metres? No, I doubt it.