You must ensure that the tyres you are driving on have more than 1.6 mm of tread on them.
Most new tyres have about 8 mm of tread pattern when manufactured but as tyres wear their ability to disperse water reduces. Tyres should be replaced before the tread wears down to the level of the Tread Wear Indicators. This can be checked easily with the help of a tread depth gauge or visiting your nearest Apollo dealer.
Tread Wear Indicators are moulded into all major grooves of tyres in at least four positions around the tyre. These indicators sit at least 1.6 mm above the bottom of the grooves and should be examined regularly and should be replaced when at the wearing limit.