The current Tower Bridge was designed by Mott, Hay and Anderson and opened by the Queen in March 1973.
It is a three span pre-stressed concrete box girder structure with a total length of 283m and carries about 40,000 vehicles a day on the A3 over the Thames.
While there is no weight limit on the bridge itself, there is a weight limit in Eastcheap and Gracechurch Street on the north side of the bridge, details of which can be found at Weight Limits.