Roadside

What are these bollards on the pavements near the roads around here? On my way back form the gym this evening (really happy I went again) I noticed this one. I must have walked past it a hundred times or more but it’s not clear what they are. Given the colouring, I am assuming they are some kind of marker to traffic to indicate the edge of the road. But they have holes at the top that are intriguing. As a sign that people are moving out of lockdown, I was unable to grab a picture without a car in the background somewhere: there is more traffic on the roads.