Buses and trams ply the streets from 5am to 11pm each day and are the cheapest way to get around. Tickets are valid for all modes of public transport and must be bought in advance. The metro trains run frequently between the southern suburbs and the city centre and are the fastest way of getting around Warsaw.Metered taxis can be hailed on the streets or ordered by telephone from a number of different companies; it is best to agree on a price before getting in. Taxis ordered by phone are usually a lot cheaper. Hiring a car is unnecessary except for excursions out of the city. The historic Old Town is best explored on foot and a lovely way to get around the city is provided by the rental bike system.