What purpose do the long white (pedestrian) lines serve at the ends of airport runways?

Question

Something up David Feldman's alley, the thought of it has been bugging me occasionally for years.

Answer 1

if this is right the line and number mean what way your going like 18 is going north and south 36 , lines to just see it far away,    if im reading that right

Answer 2

Those lines are called the 'Threshold' and mark how far down the taxiway you can go before getting clearance to move onto the runway.

Answer 3

They help you to see the end of the runway.  Under certain light and conditions, it can be difficult to tell where the runway actually begins.  The 'piano keys' create a contrasting pattern where at least some portion of it will be visible under all visual conditions.

Contrary to popular belief, this portion of the runway is every bit as strong as the rest of the runway and is perfectly legal to land on.  There is something called a 'displaced threshold' where they move the piano keys further along the runway for obstacle clearance on landing at some airports; but planes are allowed to take off from before the threshold.

Answer 4

Those lines are called the threshold, and they indicate the beginning of the usable portion of the runway available for landing. At some airports, you will notice those lines about 1000 feet down the runway (as an example, varies by runway and airport) That is called the displaced threshold. All of the runway before the threshold can be used for taxi and takeoff, but not for landing. This is done for several reasons, primarily, the runway before the threshold may not be strong enough to stand up to the stress of landing aircraft. Additionally, there may be obstructions such as buildings or towers, that make it impossible to maintain a safe altitude above the obstructions, while maintaing a safe descent to the runway before the lines.

Answer 5

Calnick is right on this one by saying you can land anywhere but you do have markers +- 1000ft down the runway this is called the touch down zone and is self explained. The reason why this is the is for when A/C do instrument approaches, if they do go below glide slope they will still end up on the black top and not in the trees. In normal conditions you can land anywhere you want to. A displaced threshold is shown by arrows before the threshold.