Millennium Bridge, London people walking caused small sideways oscillations in the bridge, which in turn caused people on the bridge to sway in step, increasing the amplitude of the bridge oscillations and continually reinforcing the effect. On the day of opening, the bridge was crossed by 90,000 people, with up to 2,000 on the bridge at any one time. Resonant vibrational modes due to vertical loads (such as trains, traffic, pedestrians) and wind loads are well understood in bridge design. In the case of the Millennium Bridge, because the lateral motion caused the pedestrians loading the bridge to directly participate with the bridge,
London Bridge recoup the cost of building and maintenance by licensing out building plots on the bridge but this was never enough. In 1284, in exchange for loans to Edward I, the City of London acquired the Charter for the maintenance of the bridge, based on the duties and toll-rights of the former "Brethren of the Bridge". The bridge was wide, and about long, supported by 19 irregularly spaced arches, founded on starlings set into the river-bed. It had a drawbridge to allow for the passage of tall ships, and defensive gatehouses at both ends. By 1358 it was already crowded with