In line with karenmac, the cones are often called witches hats here in the U.S., but usually just traffice cones.
Of late, we see a lot of small (3 to 4 feet high, 3 inches in diameter) traffic dividers that are attached to the road surface somehow... never had the fortitude to stop and investigate how... they're usually of longer duration than the cones, which are often blown away here in the western U.S. winds...