When there's a meaningful road curve approaching, you may want to get a simple visual hint of the distances in question — how long the turn will be, where exactly you are at any given moment, etc. For this, dotted marks come in handy.
Bearing in mind that the distance between the dots equals to 50 meters, you can estimate the situation quite precisely. They act as an additional tool for better recognition of the road ahead. To enable them, access the HUD options panel and tap the button with dots (). Then, you'll see them appeared on the road curve on youre windshield, like it's depicted o the screenshot below: