Surface railways are the cheapest and most extensively used form of railway service in the world. In such a system, the track is laid on a ground that has a suitable embankment or cutting, depending upon the topography of the area. Metropolitan railways use electric traction because of the following advantages.
(a) Electric traction does not pollute the environment.
(b) The acceleration and deceleration of trains is faster.
(c) Electric traction ensures the availability of power for improved and modern signalling.
(d) An electric locomotive can haul a train with the same efficiency in both the directions and there is no need for reversing the direction of the locomotive.
(e) This system uses special type of coaches called electric multiple units (EMUs), which can carry more traffic than conventional coaches.
The construction of surface railways with an overhead electric transmission system is quite costly and comes to about Rs 10 to 15 million per km (excluding the cost of the land) in normal terrain. The cost, however, increases considerably in dense and thickly populated areas, where the cost of the land to be acquired is quite steep. In addition, the railway line may have to be constructed across roads, some of which may be quite busy.
Type of crossings
The points where the roadways and the railways cross each other are provided with a level crossing, a road under bridge, or a road over bridge, depending upon the volume of traffic being carried by rail or road, availability of financial resources, road level vis-à-vis rail level, proximity of land, and other allied factors. The special characteristics of each one of these crossings are given in subsequent paragraphs.
Level crossing At this crossing, the railway track and the road cross each other at the same level. In urban areas, most level crossings are manned by two to three watchmen who are responsible for operating the same. Normally the level crossing remains closed to road traffic and is opened only when road vehicles need to cross to the other side. Though quite cheap and convenient, level crossings have the following limitations.
Gatemen have to be provided for manning level crossings, which proves to be quite costly.
(b) Level crossings cause delay in the movement of road traffic, particularly when trains are crossing them.
(c) Level crossings pose a significant safety hazard and the number of accidents at level crossings is quite substantial.
Road-over-bridge The road over bridge is a kind of bridge where the road passes over the railway line. It is an improvement over the level crossing and overcomes most of the limitations of a level crossing are. However, the road over bridge has certain limitations, which are as follows.
(a) The road-over-bridge is a costly arrangement, as apart from the cost of construction of the main bridge, heavy expenditure is involved in constructing the road approaches and acquiring land.
(b) The length of the detour provided for crossing the track is considerable, particularly for cyclists and pedestrians. In some sections, therefore, a foot over bridge is provided so that at least pedestrians and cyclists can use it to cross the track.
Road-under-bridge In this instance, the road passes under the railway line. A road-under-bridge is preferred in places where the general ground level is low and the railway line is at a comparatively higher level. A road under bridge is also preferred in areas where enough land is not available. Normally, a road under bridge costs less, but its construction is quite complicated. The cost may also increase if excavation is required in rocky areas. If the water table is high, there may be an additional cost involved for lowering the water table. A road under bridge normally presents drainage problems, particularly during monsoons.