The rear plate of a driver who has no transponder, fails to insert his cash card into the transponder, or fails to maintain a cash balance sufficient to pay a particular charge, is automatically photographed as it passes under a gantry. Such drivers originally had to pay a fine of SGD 70, but now pay an administrative charge of SGD 10. The charges at the central business district cordon apply on working days during daytime hours (7.30 a.m.-7 p.m.), but there are periods with zero charges (10 a.m.-noon). On other roads, charges apply during the morning peak period (7.30 a.m.-9.30 a.m.) and in some locations in the evening (5.30 p.m.-8 p.m.). The ERP system makes it possible to vary charges by location, time of day and vehicle type, so as to relate them to the actual level of congestion. The rates for different types of vehicles are set to be approximately proportional to their passenger car equivalent (PCE) values.