bridges

bridges. Britain's pre-1100 wooden bridges do not survive, except as place-names, but extensive activity continued throughout the Middle Ages, and few new bridge sites were added before 1750 to those identifiable in 1500. Bridge-building was one of the three communal obligations, an object for pious work, and for seigneurial enterprise. There had been a Roman London bridge, but its continuous history dates from that constructed of wood in 993, and rebuilt of stone from 1176. Some early bridging works were extensive: Aldreth Causeway (c.1100) was one of two constructed across the fenland to the Isle of Ely. Many towns levied pontage tolls to erect and maintain bridges, and there were also religious links: Queen Matilda endowed Barking abbey to maintain Bow bridge, c.1150, and chapels were recurrent features of medieval bridges, as at Wakefield and Derby. Bridging points formed the core of medieval new towns, such as Chelmsford (c.1200) and Leeds (1207). Bridges replaced many fords and ferries in the later Middle Ages, and indicated widespread growth of vehicular traffic. Medieval stone bridge construction was robust and coped with much traffic growth, and widening and strengthening engineering works did not become generalized until after 1750.

Responsibility for bridges lay with parishes or landowners, but uncertainty led to the statute of Bridges (1531) providing for fall-back maintenance by the county, and by 1602 48 bridges had become the responsibility of the West Riding. Heavily used bridges also required special procedures: private Acts were employed increasingly in the 18th cent. to create commissions to finance major bridges and new crossings by tolls, beginning with Westminster (1736) initiated with a dedicated lottery. General county responsibility did not come until 1888. Private Acts were thus used for many of the eight bridges added to London before 1820 (including Kew in 1759), and three of these—Vauxhall, Waterloo, and Southwark (1816, 1817, 1819)—effectively created the new suburbs of Brixton, Kennington, and Camberwell. Trunk turnpike development built major bridges, notably on Telford's Holyhead road at Conwy and the Menai Straits (1815–19).

Significant development functions came also with the great aqueducts at Barton on the Bridgwater canal (1761), which obviated the need for locks, and Telford's cast-iron construction at Pontcysyllte (1805) carrying the Ellesmere canal over the Dee at 127 feet. Ironbridge, Coalport (1779), and Sunderland (1796) pioneered the application and diffusion of cast iron to bridge construction, and laid the basis for the railways, although Brunel and Cubitt still used timber extensively in the 1840s. Railways employed brick and cast and wrought iron to bridge Britain's great estuaries and rivers between the 1840s and the 1870s: the Dee, the Severn, the Tamar, the Solway Firth, the Menai Straits, and the Tay. Even before the failure of materials and design on the last (1879), steel had established itself as the critical construction material, and demonstrated its strength in the Forth bridge (completed 1890).

Twentieth-cent. bridge-building was correspondingly dominated by steel and concrete for roads. The great railway crossings were replicated from the 1960s by road bridges, all bar the Tay on the suspension principle, and new crossings of the Thames and Humber were added. Lightweight box-girder construction speeded the building of over-bridges from the 1960s, despite initial collapses, and motorway and trunk road building provided an immense stimulus to their use: the first stretch of the M1, opened in 1959, had 183 bridges in its 75 miles, and was constructed in 586 days.

J. A. Chartres