No car needed: three RTA routes run in season — 103 from Union Metro, 104 from Ghubaiba bus station, and 106 from Mall of the Emirates Metro. (A fourth, bus 102, also serves the park, but the English and Arabic pages name two different starting stations for it, so none is given here.) Buses run roughly 3:15pm to 11:15pm, and the ride itself takes about half an hour.
If you drive, three free zones serve the gates: P1, P3 and P5, each roughly 400 to 450 metres from the Gate of the World. Beyond those, paid parking runs AED 120 a day near the main entrances, or AED 75 by the Happiness Gate, and a further AED 200 buys a VIP spot — waived if you already hold a VIP Pack.