Last night, I went down to Cow Lane, not far from where I live, to see the first phase of the new rail bridges put in place. Railtrack are spending £850m on upgrading the station and tracks around Reading over the next few years, including two new platforms at the station itself, new lines, and an overhead section so that freight trains can bypass the station without getting in the way of the passenger services. As part of this, they're widening the two bridges on Cow Lane to the west of the town, which have always been a major bottleneck on that road. One (the northern bridge) is wide enough for one vehicle at a time, and the south bridge is just barely wide enough to get two cars through at the same time, if the drivers are good and going slowly. Both bridges are very low. So, they're replacing them.
Problem is, the north bridge carries pretty much all of the traffic that goes through Reading to the north and the west. The south bridge is smaller, but still carries all the goods going north or west from Southampton, so they can't really build the bridge in situ. So, what they did was to build the new bridge next to the old one, and then over the course of two days demolish the old bridge, dig and lay foundations, and then wheel the new bridge into place in one piece.
All 1000+ tonnes of it.
The original schedule was that it would take 5 hours or so to get the bridge into position, and they'd be finishing at about 1pm on Boxing day. Of course, there were unexpected delays (the geology underneath wasn't quite what they'd expected -- too much clay, more water than anticipated), so in the end they started moving it at about 1:20am on the 27th. We were there from 10:30pm, and I stayed to see the bridge lined up and positioned where they'd finally lower it in, but decided that the extra 2 hours before they could start lowering it to the foundations was a bit too much for me.
Still, I got pictures of the bridge moving into position on its transporter over the course of an hour. The transporter weighs 400 tonnes on its own, has three engines, 66 solid wheels, computer-controlled independently-drivable axles, and is brought to the site on 40 separate trucks. It's driven by one person, with two banksmen checking that it's in the right place. The narrowest part of the bridge's journey had 18cm of clearance in total, and the transporter can be placed to millimetre precision by the driver.
The cable you can see high across the gap, held up by the red tape, is all the signalling cable for large swathes of the trailway track south of Reading, controlled from the Swindon signal box.
And in 2014, they'll be doing it all again for the Cow Lane North Bridge.