Public transport in the city is cheap and generally reliable. The metro is the best way to get around the center as not many bus and tram routes go through the central zone, apart from some express buses on major thoroughfares; these are the quickest way to reach outlying areas, and cost about double the standard bus fare. The metro is fast, and despite some poorly signed stations, easier to navigate than the bus system. Buses, trolley buses and trams are well integrated and tickets are valid on all three networks, but they are usually crowded and pickpockets are a problem. There are also private minibuses that travel along the major thoroughfares and can be hailed anywhere along their route. Taxis are reasonable, but foreigners are more than likely to be overcharged. Hotels or restaurants should know the approximate fare, which can then be negotiated and a fixed price agreed before getting in. Car hire is targeted at business visitors and is quite expensive; drivers need to be 21 years of age and have a passport, international insurance policy, international driving permit and valid driver's license. Driving in the city can also be a harrowing as locals drive erratically, and roads are not well signposted.