Abstract:
The Anti-Collision Device (ACD) for the trains and the like transportation system, which prevents collision between the trains and between the train and other vehicles. The invention includes a microprocessor based central processor in the nature of a command and control unit, a receiver with a satellite signal antenna for receiving signals from a global positioning system, a crew interface of desired capacity/range with directional antenna and an Input/Output system, a brake actuator linked with the brakes for locomotive speed control, a message display unit having audio and/or visual display and a power supply system. The power supply system includes a battery and power converter, and all units and system are functionally interconnected.

Description:
RELATED U.S. APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0003]     Not applicable.  
       FIELD OF THE INVENTION  
       [0004]     This invention relates to an anti-collision device (ACD) for trains and the like transportation system. More particularly this invention relates to an ACD, mainly working on a microprocessor based system with radio-trans receiver, working in a pre-determined range of say 2 Km and having own power supply system, which when mounted on locomotive, brake van, level crossing gates, railway station or any other station automatically generates signals for converting and adopting into various safety measures such as activating braking system of a running train to retard its speed to a safe limit or completely halting the train within a safe distance, all sorts of train collisions are prevented by activating hooters at level crossing gates road users are warned and safe guarded, by activating audio/visual signals, crew member or gate man at level crossing gates are alerted to take preventive measures by recording and correcting information regarding location, speed etc. of approaching trains.  
       BACKGROUND OF THE INVENTION  
       [0005]     The collision of trains causes damage to property and life and these accidents occurring due to the collision of trains cause n1 ental trauma to the people. The various kinds of train accidents are head-on collision, side collision, rear end collision of the train and the train colliding with some other vehicles such as a bus, car etc. at the level crossing.  
         [0006]     Generally, the head-on collision of the trains used to take place due to human error. The collision of the train with other vehicles at manned and unmanned level crossing (LC) gates, occurred due to the mistake of road user or railway staff. Such incidents due to human error were generally not preventable with the available technology. This kind of mishap i.e. collision of trains which occur due to system failure or human failure can be prevented by using an Anti-Collision Device in accordance with this invention, which works automatically within a desired pre-determined range of distance.  
         [0007]     The main object of this invention is to prevent accidents i.e. collision of trains by using the Anti-Collision Device in accordance with this invention. The Anti-Collision Device when mounted on a locomotive and guard van of a train, prevents collision at speeds higher than 15 kmph with another running train fitted with similar ACD&#39;s, in block sections and running lines at stations, totally independent of signaling and interlocking systems currently prevailing. By networking with other ACD&#39;s fitted at stations and level crossing gates, collisions with road vehicles at level crossing gates and other accidents can also be avoided, thus providing a silent safety shield.  
         [0008]     Another object of this invention is to provide an anti collision device for trains which works automatically, having its own power source and which actively operates within a desired pre-determined range of distance, so that trains move at safe speed when approaching one another without colliding and in case, the inter-se distance reduces, their relatives speeds are automatically controlled.  
         [0009]     Another object of this invention is to provide an Anti-Collision Device which also acts as an alertness check device for the running staff and serves as a warning device for the driver to look for the first stop signal as the train approaches a station.  
         [0010]     A further object of this invention is to provide an Anti-Collision Device which prevents head-on collision of the trains by stopping the train automatically by remote control without the involvement of the train crew and the Anti-Collision Device also acts as a warning device for commuters against approaching trains at level crossings.  
         [0011]     In accordance with a feature of this invention, while exiting a station area where the train had arrived earlier, the deviation count at the time of exit is used to determine whether the train is dispatched on an expected correct line or not.  
         [0012]     The deviation count is the difference between the assigned number of the line a train enters a station, and the assigned number of the line along which it exits.  
         [0013]     In any given yard it is possible to uniquely work out the deviation count required from a given starting line to reach a specified line, and the station ACD carries this knowledge, which it shares with the loco ACD.  
         [0014]     This is explained further in  FIGS. 2 and 3  of the accompanying drawings.  
         [0015]     In  FIGS. 2 and 3  of the accompanying drawings, DC means Deviation count as defined, LDC means Left Deviation Count, (Left or Right is with reference to direction of movement as one enters station area), RDC is Right Deviation Count.  
         [0016]     If the block section type is same on either side of the station that is either single line or double line, the number of LDC as the train enters a station area must be same as the number of RDC while exiting, for the train to go on the right track.  
         [0017]     But if a double line block section is on one side and single line section is on the other side, then a residual count of either right or left will be predefined for the station yard-to know that exit line is right for the train leaving the station area. The scheme shown in  FIGS. 2 and 3  of the accompanying drawings are self explanatory and illustrates this feature of the invention.  
         [0018]     With reference to direction of movement, left or right deviation counts, progressively indicates the line number from the entry line to left or right-where the ACD has reached.  
         [0019]     For example, for an upcoming train entering, if ACD executes one left deviation only, then it has rolled on to a line adjacent and on left to the Up main line.  
         [0020]     Suppose the train has to exit now this line on the right Up line, it must execute one right deviation; if it executes more than that, then obviously the train has entered NOT-the correct Up exit line-but a wrong one.  
       BRIEF SUMMARY OF THE INVENTION  
       [0021]     According to this invention, there is provided a system for prevention of collision in a railway network consisting of a plurality locomotives moving on a plurality of tracks, said tracks passing through a plurality of stationary structures, such as stations, gated and unmanned and grade crossings, sidings, switching locations and yards, said system comprising: 
        [i] at least one central processing unit for receiving and processing signals fitted in each of the trains;     [ii] at least one processing unit for receiving and processing signals fitted in each of the stations;     [iii] at least one processing unit for receiving and processing signals fitted at each of the crossings;     [iv] a global positioning system signal receiving means cooperating with the said central processing means fitted in the trains;     [v] radio signal transmitting and receiving means cooperating with each of the said central processing means;     [vi] said central processing means fitted in the trains adapted to receive and process signals received from the global positioning system signal receiving means, generate response signals and transmit the said response signals via the said radio signal transmitting and receiving means, in real time identifying the location and velocity of each of the trains and said central processing means adapted to receiving signals for the identification of track on which the trains are moving;     [vii] said central processing means adapted to receive via the said radio signal transmitting means said response signals;     [viii] said central processing means in the trains further adapted to generate emergency signals in response to specific potential collision identifying response signals; and     [ix] brake actuation means cooperating with the central processing means fitted in the trains adapted to receive the said emergency signals and cause the brakes of the trains to be applied in an emergency.        
 
         [0031]     The present invention relates to an Anti-Collision Device (ACD) for the trains and the like transportation system, which prevents collision between the trains and between the train and other vehicles. Accordingly this invention provides an anti-collision device for trains and the like transportation system comprising a microprocessor based central processing means in the nature of a command and control unit, a receiver with a satellite signal antenna for receiving signals from a global positioning system, a crew interface of desired capacity/range with directional antenna and an Input/Output system, a brake actuation means linked with the brakes for locomotive speed control, a message display unit having audio and/or visual display means and a power supply system, preferably consisting of a battery and power converter, all units and system being functionally interconnected.  
         [0032]     This Anti-Collision Device when mounted on locomotives, brake vans, level crossing gates, railway stations or any other station will automatically generate signals for converting and adopting various safety measures such as activating and reducing the speed of the train and bringing the train to a complete halt within a safe distance and thereby preventing collision between two trains and collision between a train and other vehicles at level crossings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0033]     The inventions will now be described with reference to accompanying drawings wherein:  
         [0034]      FIG. 1  shows a schematic diagram of the process of the present invention.  
         [0035]      FIG. 2  shows a schematic diagram of the present invention for explaining the deviation count feature for a double line block section; and  
         [0036]      FIG. 3  shows another schematic diagram of the present invention for further explaining the deviation count feature in an alternative embodiment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     Referring to  FIG. 1  of the accompanying drawings, the anti-collision device, according to this invention, mainly comprises a central processing unit being a command and control unit (CCU) ( 1 ) consisting of microprocessor base module for processing data and generating commands from the ACD, a Global Positioning System receiver  3  picks up, signals through satellites and submits the same to CCU  1  for deciphering to extract the parameters related to the movement of locomotive, like latitude, longitude, speed, date and time etc. The antenna of the GPS receiver  3  is fitted on the rooftop of the locomotive.  
         [0038]     A crew interface and, data entry key pad ( 4 ) helps the driver/crew to feed data like train number, direction of travel (whether Up or Dn) and running on RIGHT or WRONG track (which may be changed at any station, if the situation so arises) at the beginning of the train journey. A Radio Trans Receiver ( 5 ) of desired capacity/range transmits the information and commands being generated being sent by the similar ACDs, including station ACDs when the same, is within the radio-range (about 1.5 to 2 kms or even more). The directional antenna  11  for the radio trans receiver  5  is fitted outside the locomotive cab.  
         [0039]     An I/O sub-system ( 6 ), gives signals to braking signal unit ( 7 ), to actuate a braking mechanism (not shown) for locomotive speed control and a message display signal unit ( 8 ) having audio and/or visual display means is provided. Also included is a battery ( 9 ) with power converter ( 10 ) for power supply to the ACD. The display unit  8  has typically a screen MD and other indication means such as the SOS signal indication, an audio alarm indication A, a visual alarm indication V and an acknowledgment indicator ACK. The SOS indicator is an SOS signal generator as well and immediately gives an overriding SOS signal to all similar devices in the section. The acknowledgment indicator ACK is used to acknowledge an alarm signal by the crew and for resetting the other alarm indicators.  
         [0040]     As a result of the processing of information received from other ACDs, the command and Control Unit takes a decision for applying either a normal brake or an emergency on the locomotive, as the case may be. The electro-pneumatic braking is then applied through a suitable solenoid interface, well known in the art, for this purpose in the cab of locomotive. The central processing means  1  is adapted to receive signals for the identification of track assigned a unique number on which the trains are moving in a section of the network based on the deviation count and to compare this assigned unique number with the assigned number of the tracks of other trains moving in the same section.  
         [0041]     The ACDs on the locomotives as well as those provided at unmanned as well as manned non-interlocked Level Crossing Gates exchange their identification details with relevant data enroute through digitally encoded data packets when they come within the radio range of each other. Based on the analysis of the data personnel at the Level Crossing Gate or in the Guard&#39;s Van will then initiate necessary action.  
         [0042]     Functional Requirement Specifications:  
         [0043]     The functional requirement specifications are described individually for each type of ACD viz, 
        [1] Loco ACD     [2] Station ACD     [3] Guard ACD     [4] Level Crossing ACD        
 
         [0048]     Loco ACD:  
         [0049]     (i) The Loco ACD should detect and identify all ACDs within 3 km range whether it is a loco or station or guard or level crossing ACD and clearly and uniquely identify a multiple number of the same type.  
         [0050]     (ii) From each type of ACDs the data packet received should be analyzed to determine if the other ACD is a loco. If both are Loco ACDs, the loco ACD, based on information received from the GPS must detect if the relative distance between them is reducing and also detect if both are moving on the same track, if so, initiate action to warn the drivers through audio-visual indications and initiate appropriate braking action automatically to avoid collision, when relative distance is reducing. The loco ACD also detects any unusual stopping of the other ACD when it is not in a station area, but on a right track line, and checks for normalcy signal from the other ACD; if not present, one corrective step that the processor may take is slowing down the train while giving audio-visual indications, to 25 kmph, or less as prescribed. The loco ACD should also detect any SOS signal if transmitted by any other ACD within 3 to 4 km and should immediately apply appropriate braking, while warning the driver in a station area should if the other ACD is fouling tracks.  
         [0051]     (iii) If the other ACD is station ACD, the loco ACD should: Get knowledge of station main line occupation; Get information of first stop signal locations of current and station ahead, to alert loco driver through audio-visual warnings demanding acknowledgment, while approaching the same; Detect any SOS and acts to stop Get information for type of block section ahead; Get information about current and station ahead running line identification in terms of deviation count numbers; Detect if any train&#39;s rear end is fouling from the station ACD; and Give information about defective gate ACD in block section in rear.  
         [0052]     (iv) If the other ACD is a level crossing ACD-manned with gates, the loco ACD should: Detect if the gate is open and reduce speed to 25 kmph; Detect SOS and stop train; Detect if gate ACD is defective; and Automatically initiate whistling by the loco while approaching the gate.  
         [0053]     (v) If the other ACD is level crossing unmanned, the loco ACD should: Automatically whistle while approaching the gate; Detect possible obstruction of track and slow train to 25 kmph; and Detect if gate ACD is defective.  
         [0054]     (vi) If the other ACD is a guard ACD, the loco ACD should: Identify own train guard ACD; Detect if continuing with the train maintaining integrity, if parting is detected, driver should be warned; Detect in station area whether guard ACD cleared the cross over in rear as well as fouling mark; Detect if guard ACD is defective; and Detect SOS from guard ACD and stops train.  
         [0055]     (vii) On it&#39;s own, the loco ACD should: Detect in station area on which line it is standing, while departing determine whether in fact moving on right or wrong line, whatever be the written declaration of station staff; Detect, if the ACD mounted loco, in station area, is fouling any tracks; Detect alertness of running staff on the loco in normal run in block section and as it approaches the first stop signal-absence of alertness should slow down of train; Conduct self-check and advise if not working as per specifications; and Should detect if running staff on loco are under duress.  
         [0056]     Station ACD:  
         [0057]     (i) Within 3 km range, the Station ACD should be able to identify the type of ACD i.e., loco, guard and uniquely identify each one of them when more than one is present. The station ACD should detect the ACD and the line it is occupying based typically in accordance with a preferred embodiment of this invention on the deviation count, and should advise the deviation count from the line of entry from block section vs. the line number in the station, should have the deviation count for correct exit line from the station from any dispatch line, should advise deviation count information as above for station ahead, should advise the location of first stop signals for current and next station ahead, advise the types of two block sections ahead, advise the locations of ACD fitted level crossing gates in the two block sections ahead, should detect loco/guard ACD fouling any line in the yard, should start siren or hooter if a guard ACD is detected to be rolling back into station, should detect if any facing point on the main line is set to loop, and should conduct self-check and advise if not working to specifications. In accordance with this invention, this information is transmitted by the station ACD to the Loco ACD for continuously processing this information at the Loco ACD  
         [0058]     Guard ACD:  
         [0059]     The Guard ACD should uniquely identify the ACD in a range of 3 km or twice the emergency braking distance required, should derive own identity from loco ACD of nominated train-from declared train number, monitor for alertness of guard, should detect if train parting has taken place, should generate SOS signal if parting takes place, should allow manual generation of SOS, should have long stand alone power supply system for over 12 hour working, and be portable and of brief case size to be fixed with anti theft frame on brake van or SLR.  
         [0060]     Level Crossing Gate ACD:  
         [0061]     (i) The Level crossing gate ACD should identify an approaching train ACD and warn road users with audio-visual signals, should detect gate open condition, if it is provided with gates, and warn the approaching train, should do self-check and report if defective to passing loco ACD, and should detect if road is possibly blocked and advise the approaching loco ACD.  
         [0062]     The ACD is capable of functioning with or without inputs from GPS when inputs are provided from standard digital tacho-meter normally available in locomotives coupled with angular measurements of the bogle relative to the longitudinal axis of the loco body.  
         [0063]     The above inputs make it possible for the ACDs to replace the inputs that it is getting from the GPS and act in the same manner as described above.  
         [0064]     The working of the ACD according to this invention with its Various Scenarios in Action is described herein.  
         [0065]     How ACD is Activated:  
         [0066]     If two ACDs, within 3 km range find themselves approaching each other, they check if they are on a same line, and if so, initiate action to apply brakes on both the locomotives. If two ACDs within 3 km range or as prescribed range depending upon the braking distances find themselves approaching each other, but on different lines and at normal speed, then, they just pass each other safely. But if one of them had slowed down and driver, fails to press the normalcy button, to indicate he has stopped but nothing serious for the adjacent line, then the ACD moving at normal speed will continue on it&#39;s course.  
         [0067]     If the driver has a problem or he is not yet sure, he does not press the normalcy button, speed of approaching train is brought down to 25 or 15 kmph as prescribed, to enable driver to quickly stop if he detects any obstruction.  
         [0068]     If any of these two ACDs initiated an SOS signal, because derailment is detected and adjacent track needs protection, brake application starts automatically and train is brought to halt, avoiding collision.  
         [0069]     Types of collisions and description as to how ACDs act to prevent the same occurring at dangerous speeds:  
         [0070]     (i) Head-on collisions: Head on collisions should not normally occur if all present systems of signaling and other prescribed rules are observed by staff rigorously. But when rules are not observed or flouted like drivers passing signals at danger or station masters carelessly giving memos comprising facts, thus involving occurrence of more than two or three persons failing, collisions do take place. ACD can take care at this stage independent of staff actions. Each type of head on collision is described and how the ACD protects the same.  
         [0071]     (ii) In Single Line Block Section:  
         [0072]     In conventional system, if the block section in advance is already occupied by a running train, but paper line is clear, a by-passing order to the block instruments provided, may be erroneously issued by a station master allowing another train, to enter the same block section, or if a driver mistakes some signals and passes a signal at a danger point and enters a block section; or the station is non-interlocked and station-master commits a mistake, which means more than two or three errors would have taken place, in such cases, the trains may collide head on collide if they are approaching each other.  
         [0073]     In accordance with this invention, when ACDs are fitted, since ACDs are working independent of actions of station master as well as interlocking or signals at stations, they are not influenced by these mistakes or failures. When two Loco ACDs detect each other within 3 km range, and both are on same line, since it is a case of reducing relative distance between them, braking will start and trains are brought to a stop short of each other.  
         [0074]     (iii) In Double-Line Sections:  
         [0075]     In the conventional system, generally when for some operational reasons, if a train is diverted from it&#39;s normal correct track, it has to negotiate a cross-over to change line. In such cases paper line authorities are served on the driver to proceed on to the “wrong” line. In case a station master commits a mistake, which may happen if the station also is working temporarily on a non-interlocked basis, and declares to driver that he is going on the correct and, “right” line only without being diverted, perhaps even believes so, forgetting to set, the cross over correctly, then the train can proceed on the “wrong” line and may collide with another train coming in the opposite direction following correct procedures.  
         [0076]     In accordance with this invention, when ACDs are provided, since Loco ACD is constructed in such a way that, it can detect the deviation count, based on information from the station ACD, it automatically finds out that the train has been diverted on to a wrong line, and will not allow another Loco ACD on the same line to collide with it, by braking both the trains once they detect each other within 3 km.  
         [0077]     (iv) Station Area-Single Line Sections on Either Side:  
         [0078]     In the conventional system, if a train received on the main line is stopping for signals to proceed further, as per rules another train is permitted to approach the station from the opposite side. Signals not given pending setting of route. The approaching train must stop at signal as per rules. But driver may commit a mistake and pass a signal at a danger point and head on collision takes place.  
         [0079]     In accordance with this invention, when ACDs are fitted, the Loco ACD of train received in the station and standing on the main line, by virtue of its construction identifies that deviation count is zero and hence, the line identification is transmitted to other loco ACD.  
         [0080]     A train approaching a station area from a block section knows from the station ACD that facing points are not set or not set to loop. If not set to loop, the Loco ACD of an approaching train will apply brakes to stop the train detecting another Loco ACD on the same line. If station ACD conveys that facing point is set to loop, then, even though the approaching train detects a Loco ACD standing on the main line, it will only reduce speed to 15 kmph to enter loop. At this stage, driver will have enough time to stop. If he further discovers that the loop also is occupied by another train, since Loco ACD is so constructed to know that within 3 kn1 range if two of them are approaching each other on the same line, brakes automatically apply, and hence no collision takes place.  
         [0081]     Rear-End Collisions:  
         [0082]     In the conventional system, consider a scenario when a train is received and is waiting for further line clear, say on a main line and in the meantime, another train approaches that station from the block section in the rear. A Station master will be correct in not taking off signal for the approaching station as he may need time to set route etc. and expects rightly that train will stop at the signal. However, if the driver commits a mistake and passes the signal at the danger point and he will ram into a standing train.  
         [0083]     In accordance with this invention, when fitted with ACDs, loco ACD of approaching train while demanding for alertness of driver as. the train approaches the station area to observe the first stop signal, takes action to slow down train to 15 kmph if driver is not vigilant. In case the driver also declares that he is vigilant and still tends to commit a mistake of not observing signal, the ACDs will further act; because the station ACD advises the approaching Loco ACD that, say, facing points are not set to loop, then brakes apply automatically once the other Loco ACD in station area is detected on the same line as the approaching train. In addition the Guard ACD also will act to stop the approaching train. Hence collision will be prevented.  
         [0084]     The working of the ACD according to this invention with its Various Scenarios in Action is described on the following charts and description in Table 1. of the accompanying drawings.  
         [0085]     Demarcation of Station Section from Adjacent Block Section:  
         [0086]     (i) The Station ACD will demarcate the station section between two consecutive block sections. Station ACD will continuously communicate the location details (latitude and longitude) of its first stop signal (home or outer, as the case may be, provided at either ends), to loco ACDs of all the approaching trains. Based on the information received, the “loco ACD” will then light up “Station Approaching” lamp indication and give audio indication also to alert the driver. If the driver falls to acknowledge the same within 30 seconds, the normal application of brakes will be initiated by the “Loco ACD” to bring to A STOP, irrespective of the fact that the aspect of the FIRST stop signal is in ‘ON’ or ‘OFF’ position.  
         [0087]     Locomotives Within a Station Section:  
         [0088]     (i) Once two locomotives ACDs find themselves within a station section (based on the information received from the station ACD), and their speeds are also 15 Kmph or less, they will switch over to “Receive only” mode, automatically. However, in case of emergencies, such ACDs will still be in a position to send “SOS” signals to other ACDs who are within their radio range.  
         [0089]     (ii) Locomotives (including Shunting Locos) Moving At Speeds More Than 15 Kmph In Station Section Or Moving Out Of The Station Section. The loco ACD of the train will permit resumption of transmission of its own information for the benefit of other ACDs in the vicinity when its speed in the station yard goes above 15 Kmph or the locomotive comes out of the station section (as demarcated by station ACD).  
         [0090]     Dispatching Trains On “Wrong” Line From The Station Section:  
         [0091]     After ensuring that the FIRST train on the WRONG line has already been sent with speed restriction of 25 Kmph, the station ACD will permit locomotive ACDs of subsequent trains on WRONG lines at normal speeds, by conveying such information to locomotive ACD, automatically, through radio communication. In such cases, driver will also have a facility to view such updated information on screen of loco ACD, before initiating appropriate necessary action.  
         [0092]     Additional Safety Features For Non Inter-Locked Working At Stations:  
         [0093]     (i) Station ACD will take following extra precautions, in case Non-Interlocked working has been introduced at such stations and the Station ACD has been advised of the same by Station master on duty.  
         [0094]     (ii) Station ACD will restrict the speed of ALL the approaching trains to 15 Kmph by communicating the Non-Interlocked working to their respective loco ACDs in advance.  
         [0095]     (iii) As a precaution, the Station ACD will automatically force the change over of track nomination on Loco ACDs of ALL the approaching trains to WRONG line. Due to this the default setting for loco ACDs of all the trains departing from such non-interlocked station will be “WRONG” line, unless changed otherwise by Station Master on duty to “RIGHT” line through his/her Station ACD. This will reduce the probability of head-on collision even if anyone of such trains really escape on wrong line in the block section, due to human error, either by design or by chance.  
         [0096]     Handling Failure of a Station ACD:  
         [0097]     (i) Failure of Station ACD due to any reason will result in lifting of the “MASK” of station section, which otherwise separates the jurisdiction of adjacent block sections. As a result of such failure, even in case of station section, the logic meant for block section will apply, since transceiver of ACDs of trains moving at speeds of 15 kmph or less will be in ‘receive only’ mode, the other trains can pass through that station at their normal speeds. The real safety in station yard will be ensured through, signaling system and the interlocking provided through it. In addition, pressing of “SOS” through ACD by anyone of the trains in station yard will compel the ACDs of all the other trains to being their respective trains to stop.  
         [0098]     When coupled with inputs of GPS as well as inputs coming from the tachometer and the angular measurement of the bogies, the availability and reliability of the device increases many-fold, with the result one can introduce a moving-block system on any working railway, dispensing with currently available signaling and track circuiting system.  
         [0099]     The ACD works in all kinds of signaling territory whether they are automatic block system or block section working on tokens which are the oldest systems currently surviving, that means any category of signaling from the oldest category to the most sophisticated category, the ACDs function independently and ensure that no collision takes place at a speed higher than 15 kmph so long as both the moving objects are fitted with the ACDs.  
         [0100]      FIGS. 2 and 3  which are self explanatory illustrate the deviation count feature unique to this invention.  
         [0101]      FIGS. 4 and 5  which are self explanatory provide tables of collisions.  
         [0102]     The above description and illustration are given just to understand the invention rather than to limit its scope. The ACD referred herein for trains can also be similarly adopted and used for any other transportation system.