Mounted gantries on the major roads — Sheikh Zayed, Al Garhoud bridge, and a few others — that charge AED 4 per crossing via an RFID tag on the windscreen. If you rent a car in Dubai, Salik charges will appear on your rental bill. If you buy a car, you register a card and top it up. AED 4 sounds trivial; four crossings a day for a month is AED 480.