1. Cars home
  2. Motoring Rules & Regulations

Ask an expert

Anon
By AA | Moderator | 844 Posts | 24 January 2011 at 11:25am

Are there any laws which specify the dimensions of a speed bump, specifically height?

I have recently brought a 2004 Nissan Stagea station wagon which has not been modified but find huge irregularities in speed bump dimensions some of which I cannot pass without possible damage to the vehicles under-carriage.

My car is not modified and must meet a minimum road clearance. Can installers of speed bumps get away with preventing compliant road users access to public roads?

I'm sure this is an issue lots of people have but never do anything about.

Stephen

From the "Ask Jack" archives - 17 March 2010

jbiddle
By jbiddle | Community Member | 1657 Posts | 24 January 2011 at 11:32am

There are no nationwide consistent standards for speed bump dimensions, although there are Australian/NZ guidelines which are adopted by about half the local road controlling authorities (RCA's).

You might expect that within a local authority area the bumps are built to the same dimensions, but they may differ from a neighbouring council such as in the Auckland or Wellington regions which motorists travel across.

The only technical specification appears to be to ensure that emergency service vehicles and buses can traverse the bumps without bottoming out (wheelchair-friendly buses have quite low ride height), and its not uncommon for RCAs to carry out retrospective repairs if they get it wrong.

RCAs rely on feedback from road users that the speed bumps are practical, so I'd encourage you to contact the local council about the ones you have issue with. The NZ Transport Agency is updating its traffic control devices manual, and this will include minimum national standards for speed bumps which all RCAs will have to comply with (but only for new installations after the date of implementation).