England supporters in Bucks are being asked not to paint St George's flags or red crosses on the highway network.
Buckinghamshire Highways has taken to social media and said the act is dangerous and there are many other, more appropriate ways to cheer them on.
There is also a cost to removing them, as well as a safety risk to the workers who undertake the task.
It follows a recent report of a mini white roundabout in Marlow being painted red and white.

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