The basic objective of urban transport is to provide residences with access to activity such as workplaces, schools, shopping centres, etc. The different forms of urban transport in use in most cities of the world are the following.
(b) Trolley buses
(d) Surface railways
(e) Underground railways
(f) Elevated railways
(h) Tube railways
This is the most convenient form of transport and is used extensively in metropolitan cities. These buses run mostly on diesel oil and their exhaust emissions have an adverse effect on the environment. Moreover, these buses, though very convenient for transporting passengers, have very limited seating capacity.
These are buses that derive their energy through overhead electric transmission. Trolley buses are superior to motorbuses as they do not pollute the environment. On the other hand, huge expenses are incurred in providing overhead traction for supplying power to these buses.
Tramways require a track on which the trams can run and as such require the infrastructure of a proper railway track. Their initial cost is quite high. They cause minimal air pollution; however, they contribute significantly to noise pollution. Tramways are almost obsolete now and are used only in some parts of the country such as in Kolkata.
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-a-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.
(a) 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.
In such a system, the railway line is constructed below the ground level. The requisite construction work is done mostly by the 'cut and cover method'. The area is excavated in the shape of trenches and once the formation is ready, the track is laid, the necessary overhead structures are provided, and finally the trenches are covered and the ground is restored to its original state.
An underground railway system normally uses 'electric traction', as steam and diesel tractions produce smoke and lead to the pollution of the environment, which in this case becomes particularly hazardous since these railways are underground. Proper arrangements are also made for the drainage of underground railways as the low-lying areas in which they are constructed are likely to get flooded during the rains. Such underground railways have been constructed in Kolkata and Delhi and in other countries around the world.
The main advantages and limitations of underground railways are as follows.
(a) Trains can run fast and unobstructed in an underground railway system as there are no road crossings or other similar problems.
(b) As the trains move at incredible speeds, underground railways can deal with a very high concentration of human traffic.
(c) There is no wastage of land and a large area of the city, which would have otherwise been used for surface railways, remains available for other utilities.
(d) Provides safety from aerial attacks, particularly during war.
(a) The underground railway system is a very costly arrangement and a heavy financial backing is required. The cost may vary anywhere from Rs 30 million to 100 million per km, depending upon the geographical features and other conditions.
(b) Special attention needs to be given to the drainage as well as proper ventilation of underground railways.
(c) During construction, the residents of the city are greatly inconvenienced as excavation work is normally carried out throughout the city. The water supply, electricity supply, and sewerage system of the city are also affected, as the diversion of many ofthese services is required during the constructional phase.
Cross section of an underground railway
An underground railway may have either one of the following cross sections depending upon the method used in its construction.
Cut and cover In this case, excavation is done by the cut and cover method. This method affects all public services such as water supply, sewerage mains and electric and telephone lines, which have to be diverted or suspended temporarily. The typical cross section of an underground railway constructed using the cut and cover method is given in Fig. 29.1.
Fig. 29.1 Typical cross section of an underground railway (cut and cover method); all dimensions in mm
Tunnel section The tunnel for the underground railway is dug very deep into the ground, much below the level at which the ground is dug for water and sewerage mains and for telephone and electric lines. The circular cross section of the tunnel is sometimes made by the application of modern techniques that involve pushing a
big pipe of an adequate size through the ground. The necessary infrastructure is then provided within this circular tunnel. The typical cross section of such an arrangement is shown in Fig. 29.2.
Fig. 29.2 Typical cross section of an underground railway (tunnel section); all dimensions in mm
This type of railway is provided at an elevation above the ground level. The track is laid on a deck, which is supported by steel or RCC columns. The platforms and even the station building are provided at an elevation for the convenience of passengers. The typical cross section of an elevated railway system is illustrated in Fig. 29.3. The main advantage of elevated railways is that they do not require any separate land. There is no interference with road traffic as roads can be provided between the columns. Elevated railways, however, have the following limitations.
(a) The cost of constructing such a railway is very high.
(b) There is heavy noise pollution because all its components are out in the open.
(c) In the case of accidents on elevated railways, the loss of life and property is very high.
The monorail is a form of elevated railway that is provided with only one rail on which trains run. The trains can be suspended on the monorail as in Montreal, Canada, or can be mounted on pylons as in Tokyo, Japan. The monorail system is recommended only in exceptional cases where operating the conventional systems is difficult.
Fig. 29.3 Typical cross section of an elevated railway (all dimensions in mm)
In this rail system, the underground railways are generally provided at a depth of more than 25 m. The railway line is constructed in a tunnel that is circular or tubular. The main reason for taking the railway so deep into the ground is to avoid it interfering with the water supply mains, sewerage system, telephone lines, gas lines, etc., which are normally located within 10 m of the natural ground. Some of the salient features of the tube railway are given below.
(a) The railway stations of the tube railway are generally cylindrical in shape.
(b) Only electric traction is used for hauling trains in order to avoid smoke and the resulting environmental pollution.
(c) For the convenience of passengers, escalators are provided for accessing and existing the stations.
(d) An automatic signal is provided for the faster and effective movement of trains. The trains stop automatically when the signal indicates impending danger. Human error is thus avoided to the maximum possible extent.
(e) In order to ensure the safety of passengers, it is essential that the doors of the compartments are closed before the train can start. This is done by means of a centrally operated switch installed in the driver's cabin.
(f) Automatic ticket issuing machines are installed in the concourse in order to reduce the need for manpower and to ascertain that tickets are issued speedily for the convenience of passengers.
(g) Adequate indication and warning boards are displayed at significant locations so that the passengers have ready information regarding the timing of the trains and the platform number for each train without making too many enquiries.
Superiority of rail transport over road transport
Rail transport is becoming increasingly popular all over the world as far as its relation to urban transport is concerned. This is due to the following advantages that rail transport has over a road transport system.
(a) Its passenger carrying capacity per lane space is 10 times more than that of road transport.
(b) It is less prone to accidents and, therefore, the loss of life is less as against the frequent road accidents due to acute congestion on the roads that take a heavy toll on life.
(c) It has an inherent advantage in respect of reduced levels of air, noise, and other forms of environmental pollution. It is free from smoke and dust, which cause serious health problems.
(d) It ensures energy conservation, as it is run on electricity, whereas road vehicles depend on oil the world reserves of which are fast running out.
(e) It is cheaper than road transport. The subsidy required for rail transport per kilometre is less than that required for road transport.
Study of MRTS
It has been experienced the world over that road transport alone cannot efficiently meet the needs of intra-urban transport in the case of large cities. Rail-based mass transport has been found necessary for keeping road congestion within acceptable limits. The need for a rail-based mass rapid transport system for the four metropolitan cities of India, namely, Delhi, Kolkata, Mumbai, and Chennai, was recognized in the early 1970s. Accordingly, the Planning Commission set up MRTS study teams for each of the four cities under the guidance of the Ministry of Railways. The study reports were finalized in the mid-1970s. On account of the massive investments that were required and the simultaneous paucity of funds, the project remained on paper except for a corridor in Kolkata, which was taken up subsequently. For various reasons, progress on the Kolkata project was slow and was commercially operated for the first time in October 1984.