Yellow taxis run by the meter. Some taxis are air-conditioned at no extra charge. They are illegal, and probably mean the driver is trying to take advantage of you. Hail the next cab. We've heard of taxis trying to pull this dirty trick right out a couple of 5-star hotels, the bus station, domestic airport and even a major mall in Botafogo .
Cars are bigger and usually air-conditioned.
Call one of the companies providing this kind of service and tell them where to pick you up, where to drop you off, and at what time. Some radio-taxis charge by the meter, others charge flat rates. Ask for all details first. They will ask for a contact phone and call you back to confirm the ride. Rio's subway is still relatively small, but it is very safe, comfortable and reliable.