The overall aim concerning the use of tyres for improvement of traffic safety.
Centrally to this, is the idea that end users need to make the correct assessment in relation to the tyre condition in order to achieve a level of safety as high as possible. Within this context, the tyre condition is considered in relation to technical elements (tyre inflation pressure, tyre tread depth, tyre damage, tyre age, and meteorological influences) and one information element (driver awareness).
TWI Tread-wear indicators (TWI) means the projections within the tread grooves designed to give a visual indication of the degree of wear of the tread.
Tyre worn beyond TWI
Tyres with Non Skid Depth (N.S.D.) less than 0.8mm for two and three wheeler tyres and 1.6 mm for other motor vehicles tyres are unsafe to drive. Tyres worn beyond these limits are not fit for use.
Every tyre has “TWI bars” in the main grooves and TWI indicators in the shoulder region on at least 6 locations around the circumference.
Different manufacturers use different marks / symbols to indicate TWI