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 138 shops. At least one two-entranced, multi-seated public latrine overhung the bridge parapets and discharged into the river below; so did an unknown number of private latrines reserved for Bridge householders or shopkeepers and bridge officials. In 1382–83 a new latrine was made (or an old one replaced) at considerable cost, at the northern end of the bridge. The buildings on London Bridge were a major fire hazard and increased the load on its arches, several of which had to be rebuilt over the centuries. In 1212, perhaps the greatest of the early fires of London broke out on both