You can buy a Singletrip Metroticket
(as opposed to a Two Section Metroticket) which allows you unlimited transfers to other train, tram or bus services for two hours - the full fare is $5.00 (called "All Times") or $3.10 ("Interpeak" between 9am-3pm on weekdays, all day on Sundays and public holidays).
Trains and trams have ticket machines on board which sell Singletrip, two section and daytrip tickets (unlimited transfers until last service) and take coins or VISA/MasterCard/EFTPOS cards, while bus drivers sell these on request and will give change for small value notes.
There is also the Metrocard
system which uses a smart card with a money balance. When you board a vehicle or enter the platform area at Adelaide Station, the price of a Metrocard fare is deducted from your card's balance and then you get two hours of unlimited transfers. The All Times fare is $3.29 and the Interpeak fare is $1.80, which works out to about a 30-35% discount compared to buying Singletrips. When your balance runs out (it is displayed on the validator screen every time you touch on) you can 'recharge' it at a train vending machine, at the large vending machines at Adelaide Station (these take notes as well as coins or cards), at third party retail outlets (a list and map is online) or with your VISA/MasterCard credit card on the Adelaide Metro website.
You can also purchase a 28 day pass for your Metrocard which gives unlimited travel for four weeks making for a further 13% saving if you use the system for 20 return trips (i.e. every working day).
Bikes may be carried on all train services, and on buses or trams at the discretion of the driver (bus) or conductor (tram). On weekends, public holidays and weekday off-peak times (9am to 3pm and from 6pm to last service) they are carried for free, in weekday peak periods (first service to 9am, 3pm to 6pm) an extra Concession fare must be purchased for the bike, which can be in the form of either a Singletrip or a Metrocard.
When you make a transfer, you must validate your Metroticket/Metrocard - this is used to gather statistics on which services are being used.
The time at which you start your trip's first boarding determines whether the trip is valid as an All Times or Interpeak trip. If you board a train at 8:59am and validate immediately, then proceed to transfer to a number of other services, you will be charged the All Times rate of $5.00/$3.29. Similarly, if you board at 2:59pm and validate immediately, you can transfer onto other services right up to 4:59pm and still be charged for only the one Interpeak fare. If your two hour validity expires while you are on board, you do not have to re-validate to finish the trip.
There is no refund or compensation scheme for delayed trips outside the official margin allowed (5min for buses, 6min for trains and trams), despite the introduction of Metrocard and GPS tracking of all services potentially allowing automatic refunds to be issued to everyone who validated a Metrocard on the service which was delayed.
All the fares I've quoted are the full fares, if you have a valid concession card (e.g. full time student, DVA pension card etc) then the fares applicable are discounted by roughly half. If you do not have your concession card with you on the day and ready to be inspected by an authorised officer, you must buy a regular fare instead of the concession fare.
Seniors Card holders have their Metrocard integrated into their Seniors Card, this allows them to enjoy concession fares in peak periods and free travel in off-peak periods (all Interpeak valid times plus Saturdays and weekdays after 7pm). This is not a targeted concession which is dependent on being the recipient of welfare payments such as the aged pension, it is a government subsidy originally brought in to win the Grey Vote at the 2006 State Election.