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London's extensive Underground train (Tube) system has color-coded routes, clear signage, and many connections. Trains run out into the suburbs, and all stations are marked with the London Underground circular symbol. (Do not be confused by similar-looking signs reading "subway" this is British for "pedestrian underpass.") Trains are all one class; smoking isn't allowed on board or in the stations. There is also an Overground network serving the farther reaches of Inner London. These now accept Oyster cards.

Some lines have multiple branches (Central, District, Northern, Metropolitan, and Piccadilly), so be sure to note which branch is needed for your particular destination. Do this by noting the end destination on the lighted sign on the platform, which also tells you how long you'll have to wait until the train arrives. Compare that with the end destination of the branch you want. When the two match, that's your train.

London is divided into six concentric zones (ask at Underground ticket booths for a map and booklet, which give details of the ticket options), so be sure to buy a ticket for the correct zone or you may be liable for an on-the-spot fine of £80. Don't panic if you do forget to buy a ticket for the right zone: just tell a station attendant that you need to buy an "extension" to your ticket. Although you're meant to do that in advance, if you're an out-of-towner, they generally don't give you a hard time.

For one-way fares paid in cash, a flat £4.70 price per journey now applies across all central zones (1–2), whether you're traveling 1 stop or 12 stops. If you're planning several trips in one day, it's much cheaper to buy a visitor Oyster card or even a Travelcard, which is good for unrestricted travel on the Tube, buses, and some Overground railroads for the day. The off-peak Oyster-card fare for Zones 1–2, for example, is £2.20. An Off-Peak one-day Travelcard for Zones 1–2 costs £8.90. The more zones included in your travel, the more the Travelcard will cost. For example, Kew is Zone 4, and Heathrow is Zone 6. If you're going to be in town for several days, buy a seven-day Travelcard (£31.40 for Zones 1–2, £57.20 for Zones 1–6). Children 11–15 can travel at discounted rates on the Tube and free on buses and trams with an Oyster photocard (order at least four weeks before date of travel), while children under 11 travel free on the Tube if accompanied by an adult or with an Oyster photocard and on buses at all times. Young people 16–18 and students over 18 get discounted Tube fares with an Oyster photocard.

Oyster cards are "smart cards" that can be charged with a cash value and then used for discounted travel throughout the city. A Visitor Oyster card, which you must buy before arriving in the United Kingdom, costs £3. Normal Oyster cards cost £5. Each time you take the Tube or bus, you place the blue card on the yellow readers at the entrance and the amount of your fare is deducted. Passengers using Oyster cards pay lower rates. Oyster-card Tube fares start at £1.60 and go up depending on the number of zones you're covering, time of day, and whether you're traveling into Zone 1. You can open an Oyster account online or pick up an Oyster card at any London Underground station, and then prepay any amount you wish for your expected travel while in the city. Using an Oyster card, bus fares are £1.45 instead of £2.40. If you make numerous journeys in a single day, your Oyster card deductions will always be capped: at £6.40 for travel in Zones 1–2 and £7.50 for Zones 1–3.

However, although Oyster cards sound like the way of the future, they will soon be a thing of the past. Starting in 2015, Oyster cards will begin to be gradually phased out and passengers encouraged to move to a system of direct payments using their bank debit or credit cards. In practice, this will mean swiping a "contactless" bank card instead of your Oyster card at ticket barriers.

Starting in late 2015, Tube trains will run for 24 hours a day on weekends on five major lines: Piccadilly, Victoria, Northern, Central, and Jubilee. If successful, this initiative will be expanded to other lines. Until then, the usual timetable will apply on all lines, with trains running from just after 5 am Monday–Saturday, and with the last services leaving central London between midnight and 12:30 am. On Sunday, trains start two hours later and finish about an hour earlier. The frequency of trains depends on the route and the time of day, but normally you should not have to wait more than 10 minutes in central areas.

There are TfL Travel Information Centres at the following Tube stations: Euston and Liverpool Street (open 7:15 am–7 pm), Piccadilly Circus (8 am–7 pm), King's Cross and Victoria open 7:15 am–8 pm); and at Heathrow Airport (in Terminals 1, 2, and 3), open 7:30 am–10 pm. New Visitor Information Centres are due to open at Paddington Station and Gatwick airport (North Terminal) in December 2015.

Important note: As with the Metro system in Paris—and unlike the subway system in New York City—you need to have your ticket (Oyster-card, Travelcard, or regular ticket) handy in order to exit the turnstiles of the Tube system, not just to enter them.

Information

Transport for London. 0343/222–1234; www.tfl.gov.uk.