Sydney has had 50k in suburban areas for some time. I drive 32k to work and pass through 40, 50, 60, 70, 80 and 90k speed zones and this does not include those mobile 40k limits when buses are stopped (which I note everyone ignores).
This is all within city limits and quite frankly bloody ridiculous. Heaven help any visitor to the area. With the density of Sydney's traffic and all the advertising, road advisory and other bullshit signs spread around our road sides it is so easy to miss a speed limit change sign.