DRIVING without a valid supplementary licence is the most common off-peak car (OPC) offence, according to Land Transport Authority figures. It accounts for 376 of the 673 OPC offences booked from January to July. The 376 represents a 70 per cent rise from the corresponding period last year. The other two OPC offences are driving without a supplementary licence (116) and tampering with a supplementary licence (181).