Most modern North American, some European and Japanese cars have an automatic transmission that selects an appropriate gear ratio without any operator intervention. They primarily use hydraulics to select gears, depending on pressure exerted by fluid within the transmission assembly. Rather than using a clutch to engage the transmission, a fluid flywheel, or torque converter is placed in between the engine and transmission. It is possible for the driver to control the number of gears in use or select reverse, though precise control of which gear is in use may or may not be possible.
There are also different fares which correspond to the length of time for which the tickets are valid. These fares, with a set time established on the ticket, permit the unlimited use of the Tren Urbano and the buses of the AMA. There are four types of ticket in this category. The first offers an unlimited service for one day and costs $ US . One can add to this a weekly pass for $ US , a 30 day pass for $ US , or, the most extensive, a 90 day pass for $ US . These can be obtained from ticket machines located throughout the system and can be paid for with cash, debit cards, or Visa and MasterCard.