London Underground ticketing London Underground ticketing The London Underground metro system of London, England uses a mix of paper and electronic smart-card ticketing. London Underground uses Transport for London's Travelcard zones to calculate fares, including fares on the Underground only. Travelcard Zone 1 is the most central, with a boundary just outside the Circle line and Travelcard Zone 6 is the most outlying zone covering any of Greater London and it includes London Heathrow Airport. All of Greater London is covered by zones 1 to 6. Tickets including zone 1 are usually more expensive than those involving only outer zones. The most popular
Too connected to fail Too connected to fail The "too connected to fail" (TCTF) concept refers to a financial institution which is so connected to other institutions that its failure would probably lead to a huge turnover in the whole system. Contrary to the "too big to fail" theory, this approach takes into consideration the highly connected network feature of the financial system rather than the absolute size of one particular institution. The 2007/2008 financial crisis highlighted that a small turmoil can cause a big fallback in the financial system – mainly because financial institutions form a highly interconnected network. From a network science