Cash Machine

An ATM (also called Cash Machine in RCT2) is a stall guests use if they run low on funds. These are useful in pay-per-ride parks, as they allow guests to get more money to spend in your park, rather than leaving once they have spent the money they brought with them. If, however, these are not present, guests who have spent their money will see no point in staying in the park and will return home.

Trivia
In RCT3, if you look closely at the ATM's medallion, you can see that there is a very early RollerCoaster Tycoon 3 logo from around late 2003 to early 2004.