Collard

Bollard collar, a circular piece of hardware installed in the ground that holds a bollard. Collards tend to stick up from the ground a few inches and can be very difficult to see.

Collards are usually left behind even when a bollard is removed which can be more dangerous because cyclists are less likely to see them.

Reference
Comes from combining the term bollard collar into one word. It has nothing to do with collard greens, even if it may be disliked much more than the food.

Forum Introduction

 * Hazardous Bollard and Bollard Collar Map http://bikearlingtonforum.com/showthread.php?p=22194#post22194