(The following is a technical paper by Anang Pal Malik, written in 2012.It has been published at various websites and in a technical magazine of Indian Railways-Ed)
INTRODUCTION: the turnouts and loops on Indian Railway have not received the attention they deserve. Our current layouts used for the turnouts, and lengths and track structures of loops are fit up to speeds of 30 kmph only and that too is a recent improvement from the universal and still a norm of 15 kmph on loops and turnouts. The thinking which seems to have influenced the policy is that the train which is going into a loop is going to stop in any case and therefore current permitted speeds on loops and turnouts and the length of loops are okay. However fact is that the speed on turnouts and over loops is the biggest factor affecting the section capacity and average speeds on our system. Effectively our turnouts and loops constitute a speed restriction of 15 kmph-and-dead-stop at every 10 km or so i.e. the average length of the block sections on IR, and have exactly the same negative effect on the section capacity and average speeds as a similar speed restriction in mid section. This paper details the methods to remove this speed restriction and also the tremendous advantages that will be gained once this speed restriction is removed.
BACKGROUND: If we take any stretch of road of length 60 km in any city, then with simple mathematics, any vehicle travelling at 60 kmph should cover the distance in one hour. But in practice the time is higher and reaches up to 3 to 4 hours in a city like Mumbai. What trumps the mathematics? The reason is simple and straight, the vehicle is not allowed to travel at 60 kmph beyond few 100 meters at a stretch. It has to slow down or completely stop to let other vehicles to cross its path, or to merge into the traffic stream or to diverge from the traffic stream, or to overtake a slow moving vehicle or to allow a faster vehicle to overtake it. More the number of such movements across, out of or into or within traffic stream, more the slowdowns or stoppages of the vehicle and lesser the average speed.
Therefore the grade separators are being constructed across the roads all over the major cities of India to eliminate the cross movements, road are flared wide near exit and entry points to allow merging/ diverging traffic to leave the traffic stream without slowing down or to join it at the speed of the stream. Slow moving vehicles like hand cart, heavy loaded trucks are also banned from arterial roads during peak hours so that they do not disturb the average speed of the stream.
With these measures it becomes possible to raise the average speed of the stream without increasing the maximum speed, which results into lesser fuel cost, vehicle maintenance costs and lesser accidents. Therefore it can be concluded that average speed and therefore section capacity can be raised without raising the maximum speed.
APPLICATION IN THE RAILWAY: In the railways, though there are many stations where all the loops are on one side of the main lines only , leading to cross movements, still that is not the chief cause of disruption of vehicle stream.
In case of the IR, with its mixed traffic, the chief cause of the disruptions of traffic stream is differential speeds of the trains and different stoppage requirements. Our goods trains typically run at 60/75 kmph and therefore have to go into loops every time a following passenger train comes close and thus needs to overtake the goods train. Therefore average speed of a goods train is about 20-30 kmph only which has not improved in last hundred years or so. Passenger trains likewise have to make room for express trains by stopping longer at the stopping stations. And express trains stop to make way for trains like Rajdhani.
All these stoppages not only drastically reduce the average speeds; they also eat into the very precious section capacity. It is also very common for a passenger carrying train to wait at a station in the rear for the goods train ahead to enter the loop. With automatic block signaling, it will improve a bit but not to the extent it could. The reason is that currently a train enters loop at 15 kmph or in some stretches at 30 kmph. And this speed is also applicable to loco and first few vehicles behind it, because the driver has to stop in the loop therefore he continues to lose the speed as he enters the loop with the result that the guard vehicle passes over the turnout at less than the walking speed. And during this time the whole block section remains occupied. Similar action is repeated when the train leaves a loop, with loco negotiating the turnout just after starting and the rear most vehicle gaining speed only up to 15/30 kmph. Again occupying the whole block section till such time it takes from starting to reach the next block section or automatic signal. Therefore diverging and merging movements in our case take a huge toll on the average speeds and section capacity. Further in case of a passenger train which has to be taken into a loop without making the following mail/express trains slow down, the stoppage time becomes 20 to 30 minutes at the station instead of the designated 2 minutes. This has many times led to rioting/hooliganism by the passengers of such trains. In fact many commuter trains are not stopped in this manner to make way even for a train like Rajdhani Express, forcing it to crawl behind the passenger train ahead.
What are the remedies? We are not going to raise the speeds of goods train anytime soon in the future, and even if we could, they will still be affected by the passenger carrying trains entering or exiting the loops at 15 kmph. Nor can we wish away the stoppages of the passenger carrying trains. In fact stoppages only increase.
Suppose we could take out a goods train out of our traffic stream without it slowing down in the face of a faster train approaching from the rear. The approaching train would run through without knowing the presence of the goods train so taken out of a traffic stream. Likewise if a goods train or any other train is inserted into the traffic stream after it attains its full speed, it will have no effect on the speed of the stream as a whole and no train would have to slow down or wait for it to leave or enter the traffic stream that is mainline in our case. Therefore if the diverging and converging movements of the trains can be made at the full speed, they will have no effect on the average speeds and block section occupation time will be as if the train is running through it instead of stopping or starting at the station at either end. Therefore we need to go in for devices which will enable each train to leave the traffic stream (i.e. main line) at full speed and also to merge into a traffic stream (i.e. enter main line) after attaining full speed.
THE HIGH SPEED TURNOUTS: High speed turnouts coupled with high speed, longer loops can serve precisely this function. A train can leave or enter the main line at full speed if it has to negotiate a high speed turnout. On IR, after good 150 years we are now increasing speeds on turnout to 30 kmph. At some isolated locations where double line merges into single line or vice versa, turnouts with speeds up to 50 kmph have been laid. The layouts in use on IR have speed potential up to 85 kmph. On some European railways, turnouts with permissible speeds up to 200 kmph are in use.
The table below gives the potential speed of the lay outs in use on IR (sleepers to be PRC in all cases given below):
|Sr. No.||Type of the turnout (BG)||Permissible speed (kmph)|
|1||1 in 8.5 symmetrical split with curved switch||40|
|2||1 in 12 curved switch||50|
|3||1 in 16 curved switch||65|
|4||1 in 20 curved switch||85|
(Ref:Rly Bd circular no. 2005/CE-II/TK/9 dated 24/01/07)
So we can readily have turnouts with speeds of 85 kmph over them without having to go in for any imports of technology or switches/crossings. However it is proposed that we should adopt turnouts with permissible speeds up to 110 kmph universally so that the full advantage of proposed increase in speed of mail/express trains to 110 kmph can accrue.
HIGH-SPEED, LONGER LOOPS: The full potential of the high-speed turnouts will not be realized with the current length of 686 m of the loops on IR as train will have to slow down before fully leaving the main line and conversely it will not be possible for the train to attain its full speed before reaching the mainline because of the distance required for the purpose which is about 1200 meters.. Therefore it is proposed that we should have loops with a length of 3 km universally with stations ten km apart which is the approximate spacing of crossing stations currently. The main lines are to be universally non-platform lines fit for 140 kmph even at the stations like Surat, Vadodara etc.
THE PROPOSED LAYOUT WITH HIGH-SPEED TURNOUTS AND THREE KM LOOPS
With the three km loop located symmetrically with respect to the centre line of the station, the train will enter the loop at full speed which it will maintain till it leaves the mainline completely and will then slow down and come to a halt or continue to move at 10 or 15 kmph for the following train to pass, depending on the stoppage requirement at the station.. Meanwhile the mainline would become free in 35 seconds flat for a goods train running at 75 kmph as against five minutes at present. For a goods train it will take only 35 seconds to make the mainline free for a following train to pass. So we can easily have four minute time headway between trains or even lesser. Four minute time headway means five km distance headway for a goods train, 7 km for passenger train and 10 km for a Rajdhani Express running at 140 kmph. Likewise when a train will leave the station, it will first travel more than one km over the loop therefore by the time it reaches the mainline it will have attained full speed and will not affect the speed of the stream while merging in it.
With above proposed arrangement in place we should run goods trains with an 8 minute time headway that is one goods train after every 10 km which translates to one goods train in each block section of 10 km. With 8 minute headway, we can have 7.5 trains per hour and 150 goods trains per day with 20 hours of operations, leaving 4 hours daily for the maintenance in a double line section.
All passenger carrying trains will run in the 8 minute gap between two goods trains as will be shown in the following paragraphs. Since goods train will be taken out of the traffic stream at its full speed to make way for the following passenger carrying train, and likewise join the traffic speed at full speed, no passenger carrying train will know the presence of the goods train in the traffic stream and hence all the passenger carrying trains will be in addition to the 150 goods trains as proposed to be run above.
IMPLICATIONS FOR THE AVERAGE SPEED: from the above it is clear that no train will have to wait at a station in the rear for any train ahead to enter a loop.
We consider a case of Rajdhani following a goods train with a distance gap of one block section of 10 km. Suppose there are two stations A & B 10 km apart. Rajdhani at the station A means the goods train which is at the home signal of B has to enter the loop at B. it enters in 35 seconds and starts slowing down. It slows down to 10 kmph and then continues to travel at this speed and takes a total of 8 minutes to cover first two km of the loop at B. In these 8 minutes Rajdhani will have travelled a distance of 18 km. i.e. will have crossed five signals after the advance starter signal of the station B. And therefore after that the goods train will get green starter of the loop. Taking 10 minutes as the acceleration time, it will reach next station 10 km away after 14 minutes thus losing only 14 minutes (14+8-8) in letting Rajdhani Express overtake it without slowing down the Rajdhani. The maximum distance which can be possible between a Rajdhani express and a goods train would be 22 km when a goods train would be taken into a loop instead of being taken to the next station and therefore a goods train will have to spend 11 minutes i.e. the time taken by the Rajdhani to travel 25 kmph, before the goods train starts accelerating again, thus maximum possible loss of time being 17 minutes (11+14-8) in one overtaking of a goods train by a Rajdhani. The figure would be 16 km for a express train travelling at 100 kmph and thus the goods train will have to spend 13 minutes in the loop before it starts accelerating to let an express train overtake it (which will have travelled a total of 22km (16+6) so that it crosses two signals after advance starter of the station where the goods train is waiting for it to overtake) thus goods train losing 19 minutes (13+14-8) in that block section. If a goods train is overtaken by three express trains and one Rajdhani express in its entire run it will lose a maximum of 75 minutes in overtaking operations. Thus in one ten hour run (i.e. one crew run) it will travel 625 km giving average speed of 62.5 kmph. If the time tables of present mail/express trains are not recast, with their present average speeds of about 60 kmph, none will need to overtake a goods train.
And above two cases discussed are the extreme cases where distance between the train being overtaken and the train overtaking is such that the train being overtaken has to spend the maximum time in the loop, the enveloping curve. All other cases will be within this therefore as a rough approximation we can be sure of having the average speed of goods trains equal to 65 kmph, so a goods train will travel from Ghaziabad to Allahabad in 10 hours flat and will be at Mughalsarai in a total of 12 hours. And we are not yet counting on the pure goods corridors that will be created because of the longer loops and high speed turnouts. For a passenger train stopping at each station for two minutes, one minute in travelling the first one km on the loop, four minutes in deceleration, and 5 minutes in acceleration, 4.2 minutes to cover the 7 km distance from the advance starter to home, the average speed works out to 37 kmph. Out of the 16.2 minutes taken by a passenger train to cover the distance of 10 km including stopping at the stations at both the ends, 12 minutes will be spent in the loops and it will occupy mainline only for 4.2 minutes. Therefore a passenger train will not be required to overtake a goods train in normal circumstances. Also with simple calculations it can be shown that for a superfast train like Paschim Express or Kalka Mail, the average speed with the above arrangements would be about75 kmph. Therefore, a goods train running at 75 kmph would not have to stop anywhere to let a following passenger carrying train overtake it and we can easily have average goods train speeds above 70 kmph. The revolution that it will bring about cannot easily be visualized because it is so astounding, but it is true in any case. In fact by reducing axle loads to CC-2, we should raise the goods train speeds to 85 kmph so that no passenger carrying train except Rajdhani and Shatabdi Express overtakes them and they cover the distance between Kolkata- Delhi and Mumbai-Delhi in under 20 hours as a routine.
With Rajdhani running through at 140 kmph, and taking 40 minutes for 4 stops and 80 minutes for some unavoidable maintenance speed restrictions, we can have Rajdhani reaching New Delhi from Mumbai in 12 hours flat i.e. one can start from Mumbai at 8 pm and reach New Delhi at 8 pm in the morning, without any goods or passenger carrying train getting dumped for hours in some obscure loop at some godforsaken station.
It is also clear that speed restrictions would lead to bunching of trains in such a scenario, which is why a time of 4 hours has been earmarked for maintenance so that any maintenance operation has to be done without speed restrictions.
In addition, as most of our level crossing gates are at or near the stations, within the same investment we should eliminate as many as possible level crossing gates, and progressively and quickly eliminate all level crossing gates as they would reduce the section capacity in above arrangement. This will also add to the general improvement in the infrastructure of the country leading to overall savings in the economy, and also improve safety.
COST IMPLICATIONS: one kilometer of a new line costs Rs. 5.0 crore. A new loop of the 686m length CSR costs Rs 2.5 crore. So a new loop of 3 km length will cost Rs 15 crore. With two loops at each station the cost would be Rs 30 crore. With one station at every 10 km, there would be 140 stations between New Delhi and Mumbai and about 140 between New Delhi and Howrah. Therefore the cost would be about Rs 4200 crore on each leg. With Rs 50 lakh per km being the cost of automatic block signaling; about Rs 700 crore would be the cost of converting entire route between New Delhi and Mumbai into automatic block signaled route. Thus total cost of three km UP and DN loops with high speed turnouts and automatic block signaling would be about 5000 crore on each leg of the golden quadrilateral. With this expenditure we will have an inexhaustible line capacity and very high average speeds unlocking huge carrying capacity with the same assets. 10 km distance has been assumed here between such stations as currently this is the average distance between two B class stations on the GQ and with minor variations; this is going to be the average distance between two such stations.
TRAIN CONTROL INFRASTRUCTURE: It is self evident that such high density traffic cannot be controlled with a human being manning the control board. We should have computerized centralized control. The computer is to be programmed to plan all overtaking/stopping operations. The algorithm is to be so designed as to enable the computer to work out the acceleration/ deceleration characteristics of each train as it travels the first few block sections in its control in addition to having a predetermined value for each type of rake and loco combination fed into it before hand. Thus the computer, with the condition that the detention of the goods train is to be minimum and Rajdhani Express to have no detention at all, can easily plan the location where the goods train is to be taken into loop to let the Rajdhani Express to run through, and at the same time plan the path of other following trains also.
With automatic signaling in place and high speed turnouts & high-speed, longer loops our operations will get revolutionized.
- We would be running 150 goods trains in each direction per day on a double line section, still leaving 4 hours for maintenance so that speed restrictions for the maintenance would be eliminated
- With unlocking of such a huge capacity we will not need any section capacity works for many decades.
- Proposed investment will get out the maximum output from the existing investment and assets also. With such effective transport system in place, general economic environment in the country will get a boost.
- We can freely run commuter trains without creating separate corridors with no effect on the long distance and goods trains
- Average speed of goods train and consequently turn around would improve dramatically resulting into no need to procure wagons for the many decades to come. Loco availability would become double or triple as loco kilometers would improve dramatically.
- Crew requirement will also go substantially down.
- Passengers and traders would love us.
- We would put airlines and truckers out of business.
CONCLUSION: The average speed and the section capacity are two parameters that can be easily improved with the provision of high-speed turnouts and high-speed, longer loops at minimum cost and least disruption to the traffic as most of the work of providing these facilities can be done without speed restrictions and traffic blocks. Spin-offs would include elimination of the level crossings and improvement in speeds at major stations. No new investment would be needed in goods sheds, loco and wagon maintenance facilities and staff amenities and current deployment of staff would not need changes. Thus operating cost would remain at current levels.
Therefore on the two busiest arms of the golden quadrilateral and the two busy diagonals we need to:
- Lay turnouts with permissible speed of 110 kmph.
- Lay loops of 3 km length centrally located with respect to the centre line of the station.
- Install automatic block signaling on the full length. Signal spacing at 500m instead of present 1 km should also be considered, which would reduce time headway even further, leading to even higher section capacity then envisaged here. In fact we can go in for the moving block concept, raising the section capacity even higher.
- Make main lines universally non-platform lines.
- Raise speeds on the mainline even at important and junction stations like Surat, Vadodara, Ratlam, Kota etc to 140 kmph, which can be done within the investment proposed, as any lower speed will affect the section capacity. Also raise midsection speeds also to 140 kmph which can be done with minor expenditure and tweaking of alignment at few locations, as most of our permanent speed restrictions are at the major stations.
With such infrastructure in place we should further effect following changes:
- Run shorter goods train capable of slowing and speeding up quickly.
- Raise maximum speed of the goods trains to 100 kmph with the use of lower axle load and/or better designed wagons..
- Run shorter but more number of mail/express trains.
- Run crewless auto-piloted goods EMUs with one driving and one trailing coach and recapture the truck loads from the road.
- Review cost-economics viz a viz growth in traffic, of the proposed separation of goods and freight streams and various third lines. These will not be required if arrangement outlined above is adopted. Also with dramatic improvements in average speeds we will also not need separate high-speed passenger lines.