What does this sign mean?

What does this sign mean?undefined
Drive no faster than 50km/h because there's an accident ahead
Drive no faster than 20km/h as there's an accident ahead
Stop until someone removes the sign
This sign isn't valid - they're only ever in blue with white writing

Regardless of whether the sign has a blue background with white letters or a yellow background with black letters, if it displays the word "ACCIDENT," you should reduce your speed to 21 kilometers per hour.