From midnight Friday the new categories of speeding fines outlined in this year's SA Budget will be enforced, with heavy speeders hit hard.

The new demerit points/fines for offences after 1 September, 2012 include:

Drivers up to 10km/h over the limit will be fined $150 and gain two demerit points

Over 10km/h but less than 20km/h will be fined $330 and gain three demerit points

Over 20km/h but less than 30km/h will be fined $670 and gain five demerit points

Over 30km/h but less than 45km/h will be fined $800 and gain seven demerit points

Over 45km/h will be fined $900 and gain nine demerit points

General fine amounts were dropped for lesser breaches, with higher demerit point total adapted, leaving routine speeders a pay less and learn or walk option.

Minister for Road Safety, Jennifer Rankine, said repeat speeders should consider themselves warned.

Since the announcement of the new fine system some 180,000 letters had been delivered to drivers with low demerit point allowances, including learner and provisional licence holders.

Road train drivers will be hit harder financially, with over 10km/h infringements $400, 10km/h to 20km/h $500, 20km/h to 30km/h $770, 30km/h to 45km/h $900 and over 45km/h $1000.

A $60 victims of crime levy is not included.