Are concrete central reservations easier to maintain than grassed ones?

Why are some central reservations grassed and others not? Surely concrete zones are better, as lanes do not have to be closed for grass cutting, plus less maintenance is needed and therefore they're cheaper to maintain.

Money is the reason - it's incredibly expensive to do and the saving in maintenance costs would take many, many years to recover. Many motorways and recently-built dual carriageways have concrete reservations, while older ones tend to be grass.

Answered by Dan Harrison on 26 May 2010