They're short steel posts that are used as a barrier to keep traffic out of an area. If you want to see an example Google it and look at the pics.
There those short yellow post's the are too short to see when you back into them.
Steel Bollards are usually a security post to prevent 'ram raiding' of the fronts of stores and shops, most electrical/ photographic shops have them installed at the front, this helps to protect the shop frontage should a ram-raider, using a car, van or truck as a means to gain unauthorised access to a store after closing hours: .
