The towns of Arica in Chile and Tacna in Peru are separated by merely 35 miles of land. Crossing the international border between them isn't difficult, but the information on how exactly the process works is a bit scattered online, resulting in confusion and uncertainty among independent travelers. There are currently only two public ways to do this trip: by colectivo or by bus.
Prior to May 2012, there was a historic one-car train that ran the Arica-Tacna route once per day. However, due to lack of maintenance and safety issues, the service has been suspended ever since. According to this article, Peru is in the process of investing $4 million USD to revive the train, and it is expected to be operational again by December 2013.
Even taking the train into account, however, the fastest way to get from Arica to Tacna is by colectivo. Colectivos are essentially shared taxis that run the border route several times per day. The vehicles are typically older Lincoln Town Car or Ford Taurus models, and drivers will wait until there are five passengers to depart. Buses leave from the same terminal in Arica, and the cost may be slightly cheaper than colectivos. However, with room for a lot more passengers, the journey will also take longer.
I was in no rush the morning of departure, since Peru was two hours ahead of Chile, taking into account daylight savings time. I walked from the hostel to the bus terminal, which took about half an hour, and arrived at approximately 8:30 am. Be aware that the large building with the pyramidal roof is the domestic Rodoviario Terminal. Keep walking past this building until you see a sign that says Terminal Internacional.
Domestic Rodoviario Terminal
International Terminal
Once you enter the gates, the first thing you have to do is pay the international departure tax at the window immediately to your right. This token amount totals 250 CLP, or roughly $0.50 USD. Afterwards, take the slip of paper and continue into the terminal. On your left, through a short alleyway, are the buses waiting for departure to Tacna, and straight ahead are the colectivos.
Paying the departure tax
Buses through the alleyway
