Transportation / Public Transport

Buenos Aires has extensive subway and bus routes. Taxis are plentiful and fares are reasonable. Subway and taxis are generally the most effective way of moving around Buenos Aires. The so-called "remise", a type of private car service, is also widely available in downtown Buenos Aires. For security reasons, it is recommended that travelers use either remises or radio taxis, rather than hailing taxis on the street. Railroad travel is available from several stations in downtown Buenos Aires. Commuter trains link Buenos Aires with most suburban areas, and long-distance trains connect most large cities. Travel outside greater Buenos Aires can be accomplished by train, bus, or car, although air travel is recommended for many trips to the provinces, because of the distances involved.

Buses
Buenos Aires has a large network of buses, locally called "Colectivos". There are over 180  lines, each one identified with a number and different colors. Buses traverse the city continuously each hour providing access to virtually all neighborhoods.
The bus service is available all day long, though its frequency decreases after midnight. Bus stops are usually within  two to three blocks.
Tickets are sold exclusively on the bus. Only coins are accepted by the vending machines. Do not throw away the ticket until you get off the bus. Once you are ready to get off, go towards the back of the bus, ring the bell placed by the back door and wait for the bus to stop.
The fare for a ride within the city limits amounts AR$ 1.00.
For further info on specific lines, time and faretables, please refer to www.loscolectivos.com.ar/ (Spanish site).
Buenos Aires had an extensive tramway network with over 857 km (535 mi) of track, which was dismantled during the 1960´s in favor of bus transportation. A new 2-km light rail tram is being built in the Puerto Madero district, with an extension to Retiro station and La Boca in the planning stages.
The Central Bus Terminal is located in Retiro (next to the Retiro Train Terminal) and it houses dozens of private bus companies that connect Buenos Aires with the rest of Argentina and neighboring countries. There are different types of services, with wider and more comfortable seats (and sometimes light meals or snacks) and regular coaches. Fares are relatively inexpensive and it is recommended to buy the tickets with at least a week in advance. During the summer season it gets very crowded and tickets to destinations in the Atlantic coast are sold out pretty soon.

Subway (Subte)
The Buenos Aires Metro (locally known as subte, from "subterráneo", meaning "underground") is an extensive system providing access to various parts of the city. The subway system is very reliable, covers the center  and the outskirts of the city, and it's undoubtedly  the fastest and easiest way to move around Buenos Aires.
Opened in 1913, it is the oldest subway system in the Southern Hemisphere and in the Spanish-speaking world. It is still likely to see some of the original wooden cars running in line A (soon to be sent to a museum).
The system has six lines, named A to E & H, 85 stations and over 29 mi (47 km) of track.
All lines converge downtown nearby ”The City” (downtown financial district).
An expansion program is underway to enlarge existing lines deeper into the outer neighborhoods. The H line, a new north-south route, was just recently inaugurated and is comprised of only 5 stations in the meanwhile. Track length is expected to reach 55 mi (89 km) by the year 2011.
The subway runs Monday to Saturdays from 5 am to 10 pm, Sundays and holidays from 8 am to 10 pm.
Fare : AR$ 0.90.
For further info please use the subway company (Metrovías S.A.) website (english version): www.metrovias.com.ar.

Taxis and Remises
Black-and-yellow taxis roam the streets at all hours. You can either flag them on the streets or call them for a pick up  (Radio Taxis). You can notice a taxi is free to take a passenger, when the small red flag-light in its front window is turned on and says "libre" (free).
Some taxis are unlicensed (controls are not fully enforced), so visitors are advised to phone a reputable radio-link company.
Every taxi carries a digital meter that shows the ride fare you should pay.
You are not expected to tip taxi-drivers, and they should give you change to the nearest AR 10 cents. Be aware that small change is a perennial problem with taximen.
Low-fare limo services, known as remises, have become more popular in recent years. Remises are in practice similar to taxis, but they are private cars (no specific colors or signs) and you do not flag them on the streets : you have to request them by phone or in person at "Remiserías". The price of the trip is pre-arranged, so you know exactly the price of passage. Remises are very safe, commonly cheaper than taxis, and will always take the fastest route to destination (unlike many taxis). The agencies ("remiserías") are small offices or shops located throughout the city.

Railways
Argentina's extensive railway network converges on Buenos Aires. The four principal stations for both long-distance passenger services and commuter trains are Estación Retiro, Estación Constitución, Estación Once, and Estación Federico Lacroze. These four Train Terminals connect Buenos Aires with the suburbs and the rest of the country. Most lines use diesel power; some commuter lines switched to electric power during the 1980´s and 1990´s.
Retiro railway station, located in Del Libertador Ave. intersection w/ Dr. Ramos Mejía Ave., has three suburban lines : Bartolomé Mitre, Manuel Belgrano and San Martín. It is the starting point of many out of state routes heading north (among many others, to the Tigre and the delta of the River Plate).
Constitución railway station, located in Caseros Ave. / Lima St., links the city center with suburban Buenos Aires and out of state lines heading south.
Once railway station in Pueyrredón Ave. intersection w/ Bartolomé Mitre St. links the city center with suburban Buenos Aires and out of state lines heading west. 
Federico Lacroze railway station, at the intersection of Federico Lacroze and Corrientes Ave., is located across the Chacarita cemetery and links the Chacarita neighborhood with many northeast suburbs.
There is a project to build a Buenos Aires-Rosario-Córdoba high-speed railway, which would join the three largest cities in Argentina. Bids were opened in mid-2006; the only proposal standing as of June 2007 is by French firm Alstom. Financing is a major stumbling block for the project, whose start has been delayed several times.

Roadways
Buenos Aires used to be relatively congestion-free for a city of its size. Toll freeways opened in the late 1970´s by then mayor Osvaldo Cacciatore provided fast access to the downtown area, increasing the number of cars coming into the city. During Cacciatore's tenure, the streets of the downtown financial district (roughly one square kilometre in size) were declared off-limits to private cars during daytime.
Main avenues of the city include the 140 meters (460 ft) wide 9 de Julio Ave., the over 35 km (22 Mi) long Rivadavia Ave., and Corrientes Ave., the main thoroughfare of culture and entertainment. The General Paz Ave. is a motorway that surrounds Buenos Aires, thus separating the city from Buenos Aires Province.
Following the economic mini-boom of the 1990´s, more people started commuting by car, and congestion increased. Most major avenues are gridlocked at peak hours. Another source of congestion is the flight of many people to the country on weekends.
Highways are in good conditions, are wide, have fast lanes and toll booths. It is mandatory to use the seatbelt and turning at a red light is prohibited unless otherwise stated.

Car Rentals
There are many rent-a-car companies in the city with offices at the airport and in the city center. 
Drivers must be at least 21 years old, have a valid drivers license and an international credit card. The average rate for a standard car per day is between USD 80 and USD 150 with unlimited mileage.

Ferry-Boats
Ferry services are a very popular transportation for short distance trips to Uruguay.
These are a few companies that provide fast and convenient service to the cities of Colonia, Montevideo, Punta del Este and Carmelo :

Buquebus: Córdoba Ave. intersection Eduardo Madero St. (Phone : 4316-6500)
Cacciola S.A: 520 Florida St., 1st Floor, Of. 113 (Phone : 4393-6100 / 4394-5520)
Coloniaexpress :  753 Córdoba Ave. (Phone : 4313-5100)
Ferrytur: 699 Córdoba Ave. (Phone : 4315-6800)