Here's your (almost) bog-standard square-post bollard

Often found in pairs, such as these two guarding a traffic island

Sometimes they spring up in great forests of posts

These large round ones often adorn roundabouts, but also sometimes T-junctions such as this

Two designs that are common in Bradford (and elsewhere in Yorkshire)

Pivot-based bollards, introduced in the mid-2000s, are often used in locations especially vulnerable to collision

Resilient (but attractive) posts in Fenstanton