A bridge is supposed to overcome an obstacle, but sometimes a bridge itself can become an obstacle. There are many ways to overcome this problem: swing, pivot, drawbridges, tilting, and lifting. These are all forms of movable bridges. While drawbridges or bascule bridges have been in use since Ancient times, vertical lift bridges are a bit more of recent an idea.
Lift bridges rely on counterweights, and unlike drawbridges which require the weights to be considerably greater than the span to be raised, vertical lift bridges only require an equal weight. It means a heavier deck, and also higher towers or supports.
An example of a lifting bridge can be found on the Huddersfield canal at Kirklees; the Turnbridge Lift Bridge. Built in 1865, it replaced a swing bridge. There are no towers for this narrow bridge , only a frame, wheels and chains. It doesn’t need to lift high, since narrow boats have low clearances, and so it raises a mere 5. 3 metre span of decking. It used to operate with a winch and pulley system, but now has an electric motor.
But can a lift bridge be used on a grander scale? What about connecting the mainland to an island? In the county of Kent there is an island on its northern coast – Sheppey, and it is divided from the mainland by The Swale, a tidal channel that feeds into the Thames Estuary. Swale means swirling, rushing river. Up until the 20th Century, ferries crossed the channel. But the arrival of the railway meant the port of Sheerness on the Isle of Sheppey could at last be served by trains.
The first bridge was a lifting bascule bridge, and it operated from 1860. In 1922 a cargo ship collided with the bridge, closing it for 10 months. It was the start of the end for the bascule railway bridge, due to the growing demand for a road bridge.
The replacement would have to incorporate railway, road and footpath. The level of the bridge would need to remain low and without steep gradients to cater for the electrified railway line. The vertical lift bridge was a good solution because it didn’t need the heavier counterweights of the drawbridge. Construction began in 1957 and finished in 1960. Up to 30,000 vehicles crossed the bridge every day, and a high tide, the bridge’s movable span (31.2m) is raised to allow boats to pass beneath. The railway line is electrified, except for the lifted part, and without the power of the missing third electric rail, trains coast across it. Each lift of the Kingsferry Bridge has been recorded, over 100,000 of them, and it takes approximately 20 minutes to raise and lower the bridge.
By the end of 20th Century, this was unacceptably long. A new road bridge, the Sheppey Crossing, opened in 2006, directly alongside the lifting bridge, which is still in use.
So how did it get the name Kingsferry, and not Swale or Sheppey? The 1856 act that granted permission for the first bridge, was to enable the king’s ferry to be dispensed with and for a bridge to replace the ferry. (The right to levy a toll on those using a ferry was granted by Henry IV in 1401.) The name keeps the historical context in place, and even if the boats no longer go back and forth, at least they can’t get stuck under the bridge.