For most of the day, central London's public transport system was largely out of service following the complete closure of the Underground, the closure of the Zone 1 bus network, and the evacuation of incident sites such as Russell Square. Bus services restarted at 4 pm on 7 July, and most mainline railway stations resumed service soon afterward. River vessels were pressed into service to provide a free alternative to overcrowded trains and buses. Local lifeboats were required to act as safety boats, including the Sheerness lifeboat from the Isle of Sheppey in Kent. Thousands of people chose to walk home or to the nearest Zone 2 bus or railway station. Most of the Underground, apart from the stations affected by the bombs, resumed service the next morning, though some commuters chose to stay at home. Affected stretches were also closed for police investigations.