Summer has arrived and with it an increase in reported road traffic crashes. ‘Aquaplaning’ is a
term frequently heard in the search for a reason why steering and braking responses were so
weak ‘in the wet’.
Aquaplaning occurs where a wedge of water builds up between the front tyres and the road
surface which is most often due to thin or worn tyre tread. A tyre may comply with the legal
requirement – Regulation 212 (j) (ii) where the tread wear indicator is not level with the tread
depth – but the grooves not able to disperse water quickly enough. Aquaplaning can even occur
with brand new tyres.
Tread depth plays a vital role in dispersing water from the steering tyre footprint. Leading
European tyre manufacturer Continental released research data that makes an irrefutable statement –
‘Results of braking tests for more than 1,500 drivers confirm: As tread depth decreases, braking
distances increase disproportionally. At three millimeters and less, summer tyres on wet roads become
hazardous.’ The SA legal requirement imposed by a tread depth indicator is around 50% less than the
3mm that Continental recommends, and we are into summer rains on oily, tarred roads.
To keep the braking distances as short as possible on wet roads, Continental recommends that summer
tyres be replaced at 3mm.’ Regulation 212 (j) (ii) is only a legal ‘indicator’ and not a safety breakpoint.
Despite the legal consequences, ensure that tyre footprints are the best you can get. When it’s wet do
you or your fleet have enough rubber – only 3mm – to meet the road?
And when it comes to goods vehicles deal with cargo mass distribution. An overloaded drive axle
pushing an underloaded steering axle is not a good formula for driver control on a wet road.
Reference: Roadcraft – The Police Driver’s Handbook published by the UK Police Foundation
If you wish to discuss this or for more information, please contact Hennie Botha at 031 713
3146 or at 074 331 1354
