There is an up and a down arrow that you push to call the elevator, but what is the point of having 2? The buttons are all numbered anyway, so what is the point of the Up down buttons? Every elevator I have ever seen has had two buttons (unless the elevator doors were already on the top or bottom floor)
If I was on the 10th floor, and pushed the up button, and then pushed teh button for the 8th floor, what would happen? If nothing, what is the point of two buttons?
The elevator thinks you’re going up so will prioritize requests accordingly. If someone is already on the elevator, they are likely going up, so the elevator will continue upwards. Even if it is empty, if someone in a floor above you had also requested for an elevator, then the elevator would continue to go up regardless of whether you had requested a lower floor. If they then ask for a higher floor, you’d be stuck going up until such time as there are no other “up” requests. The elevator will then go down to your requested floor, possibly stopping at your original floor to service your “down” request if no other elevator had serviced it in the meantime.
Happens to me all the time when I get on the “down” elevator wanting to go up. The elevator keeps on going down. Since there’s only the basement below my floor, it’s no big deal.
Most elevators have control programs that seek to optimize their travels. To do this, it’s very helpful to know more than “there’s a guy on the 7th floor that wants an elevator” - you’d like to know that he wants to go up (in which case you pick him up on your way to take the gal on the 10th floor down) or down (in which case you stop on the 10th floor first, and the 7th floor on the way down.
The two buttons are so the elevator controller can coordinate the elevators and move people faster. Usually, it will pick up all the people going up, go to the top requested floor, and then make the trip down for the down passengers.
For example, say you have a five story building. You have passengers going up to floors 2 and 4 on the ground floor. You have passengers waiting to go down to the lobby on floors 5 and 2.
If the elevator starts at the ground floor, this is the sequence:
Ground to floor 2, let passengers off
Floor 2 to floor 4, let passengers off
Floor 4 to floor 5, pick up passenger
Floor 5 to floor 2, pick up passenger
Floor 2 to ground, let passengers off
Does that make sense? If you were waiting on floor 2 to go down and you got on when it was already going to floor 4, you’d just have to ride with it. You could press the button for the ground floor, but the elevator won’t go there until it’s completed its trip to the top floors. This page also explains it. When you have more than one elevator, the elevators are usually coordinated so you have one waiting on the top floor and one waiting on the bottom floor so the passengers dont’ have to wait very long.
When the elevator comes a light will go off telling you whether it is on its way up or if it is going down. When you push one of the two buttons you are telling the elevator which direction you wish to travel. If you are going down an up elevator may still stop just in case you want to get on.
Assuming that the car is travelling in an upward direction when you call it, If you push the ‘up’ call button when you want to go down and someone on a floor above you has also called it, there’s a strong possibility that you will find yourself going up to service their call before you turn back down to do your trip (not that it necessarily matters in the case of a single car, as, if you pressed the ‘down’ call button, the car simply wouldn’t stop at your floor until after it serviced the other passenger).
Just to add, in a certain building in NYC (IIRC 1200 AoA but don’t hold me to that) you don’t push the up/down button, you tell it which floor you want to go to. the elevator mastermind determines which elevator you should take and lets you know which elevator number you should board.