After landing, what does a sign with a black background and a white numeral indicate?

A sign with a black background and white numeral indicates the runway distance remaining in thousands of feet. This type of sign is crucial for pilots as it provides them with information about how much runway is left for takeoff or landing. For instance, if a sign displays "3," it signifies that there are 3,000 feet of runway remaining.

This information is critical for pilots to make informed decisions during landing, especially in terms of braking and stopping distances, as well as to assess whether they have enough runway left for safe operations.

The other options do not apply in this context: distance to the next airport is not indicated by a black and white numeral sign; runway width is usually shown in another format; and taxiway exit points have a distinctly different signage style. Therefore, the correct answer accurately reflects the function of the sign in question.