Town and City Bridges
Motorways, ring roads, and many other roads, large and small, have cut across or between many communities. In earlier times, railways did the same thing. Many bridges and subways were needed in order to allow people across.
Railways can present less of a problem than roads. Level crossings with automatic barriers can cope in the case of flat ground, because of the relative infrequency of trains. They are the equivalent of traffic lights for roads, but the frequency and speed of road traffic is such that pedestrians and trains are not allowed across major roads and motorways without bridges or tunnels.
As you approach or enter a large town, you are likely to go over or under a railway track, a bypass, a ring-road, or a large road such as a motorway. If you go over a bridge, then unless the route below is in a cutting, your own route will have embankments and bridges, which exert a significant effect on the area. You may even pass over something as large as the Chiswick viaduct and Hammersmith flyover. If you are going under the other route, the visual impact of your own entry is affected.
In many cases, large roads pass over smaller ones on beam bridges, which cut straight across the view, and if the major road has four or six lanes and a central reservation, the effect will be almost that of a short tunnel. Seldom do the designers make a slot in the central reservation, separating the bridge into two halves, and letting some light into the tunnel.
Here are some examples of bridges over roads into Gloucester and its suburbs.
The last five pictures above show a typical small railway bridge in a town. It comprises two separate plate girder bridges, allowing easy spanning for the decks. The bridges are rather too close to let much light in, but a wider separation would have meant wider embankments for a considerable distance, as railway tracks cannot include sharp bends.
Note the variation in the thickness horizontal plates at the top and bottom of the main I-beams, thinnest at the ends, thickest in the middle. The gaps between the plate girders are spanned by a series of smaller I-beams. These in turn are bridged by a large number of little arches, except near the abutments, it being a skew bridge. This was once a common design. It is shown in the last picture, which, like the previous one, also shows the degradation of the end wall caused by deposition of minerals from running water. Deposits like this, over tens of thousands of years, have constructed stalactites, stalagmites, and all manner of amazing shapes in caves.
These three pictures show the M5 motorway bridge over the Hucclecote road. Although the concrete has been textured at the abutments, the bridge is basically a noisy tunnel with plain concrete walls, if you are a pedestrian. Splitting the bridge at the central reservation would have let some light in: it might also have let some noise in as well, though the noise of traffic under the bridge dominates that from above.
This is a railway skew bridge near the west end of Gloucester. Part of the right hand side is chamfered. Typically for multi-arch bridges, the next arch has been colonized by a work-shop. The next picture shows two more railway arches nearby.
Besides these arches, the railway out of Gloucester station to the west crosses several roads on plate girder bridges, and also crosses the two branches of the River Severn, separated by Alney Island.
The total number of railway bridges west of Gloucester station is in fact ten, not counting a footpath near the station, in just over 2 km. In the Bristol direction there is a level crossing, seven road bridges, and three footpath bridges. In the Cheltenham direction there are two roads and a footpath. Finally there is one extra bridge where the Bristol to Cheltenham direct line by-passes Gloucester station. This is in fact the first railway bridge depicted on this page.
The grand total of crossings is 26, in about 10 km, 6 miles, of railway track. This may seem a lot, but if you draw a line across the map of a town, and see how many streets it cuts per mile, you will see that about 4 per mile is not many at all, and that a railway cuts off large areas from each other. So does a wide busy road. Transport connects distant people, but divides those close by.
Imagine what would happen if all these bridges were replaced by level crossings. Then there are the bridges across canals and rivers. Ferries may be acceptable to tourists who just want to enjoy the view, but to carry the daily traffic of pedestrians and vehicles? No, bridges have been considered indispensable for thousands of years.
Bridges in towns often join buildings on opposite sides of a street. If the design is not done carefully, the abrupt appearance and disappearance of the bridge can be quite disconcerting. The first picture shows two examples in Cheltenham: the others show bridges in Gloucester. Some buildings even include sections on legs that seem to plug into the main body of the building.
The rectangular entrance is logical, because high delivery vehicles need to pass. But although the asymmetry of the building is interesting, the white part looks like a separate building, sling between two others.
Here are some interesting old bridges in various towns.
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