Here in the US of A they are called "speed bumps" and they are found
In my daughter's apartment complex they vary from two feet wide to six feet
wide. The two foot version consists of two bumps placed two feet apart. The
other type is best approached at an angle if you value your exhaust system.
These things are found everywhere and there is no "formula" for their
construction. I saw one that was so narrow and so high it was like trying to
climb a curb. I'm glad I wasn't driving the GT6+. It nearly took the muffler
off the Buick. Some are so small as to be totally ineffective.......wonder
why they bothered.
1970 GT6+ "Ian"
Ann Arbor, Michigan
Winnipeg MB Canada