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16/07/2010

Analysis of Failures in Signaling Systems

Analysis of Failures in Signaling Systems


1. Lack of domain Knowledge in Signaling and Telecommunications Dept relating to Signaling and Traditional Route Relay interlocking Systems, This creates a technological gap between the software programmers and the Domain consultants. This leads to major errors in software, which might lead to unsafe failures of the system.

2.Increasing the complexity of the System by Employing distributed architecture, which is difficult to validate and verify and difficult to maintain, thus leading to very high time repair.

3. Extending the working scope of the Interlocking systems for monitoring and other non-Interlocking functions, which leads to degraded performance of the system.

4. Employing Non-Formal Interlocking principles instead of traditional RRI Principles leads to software complexity. For Example: The Geographical method needs every system that is installed for new Yard needs validation, which is not practicable.

5. Since the software and hardware is so complex, complete test of the system is not possible and most of the faults are revealed at the field Installation stage or during normal working of the system in field. The software is to be changed for every yard , the software structure should be in a generic form, but we seldom see a generic form and this the stage errors creep in.

6. The lack of standardization in the railway working principles and the core Interlocking principles, the software developers are forced to do changes in the software for every yard in Different railway zones, this is the time that errors in the software creep in.

7. Because of the above said reasons the Interlocking systems have failed to create the necessary confidence in the railway operators.

If we examine broadly the reasons for failure and lack of reliability and maintainability that are forced by the signal designers are as follows:

A. Lack of standardization of interlocking principles, every railway zone ( 16 railways zones in Indian railways) has its own set of rules and principles which are conflicting with other railways, this makes the life of the developers difficult because they have change their systems settings and software accordingly.

B. There is no standard book or reference available describing the core interlocking principles, since these rules are only known by the people working in this domain.

C. Increase in the complexity of the software leads to difficulty in testing, since most of the Interlocking systems are sequential machines they are error prone are very difficult to test.

Analysis by Sandeep Patalay

--RailSamachar

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PME Due Date

Master Circular No. 25



Copy of Railway Board’s letter No. 69/H/3/11 dated 06.12.1974



Subject: Implementation of the Recommendations of the Visual Sub-Committee.



6. Periodical re-examination of serving Railway Employees:



6.l. In order to ensure the continued ability of Railway employees in Classes A l, A 2, A 3, B l and B 2 to discharge their duties with safety, they will be required to appear for re-examination at the following stated intervals throughout their service as indicated below:



6.1.1. Classes A l, A 2 and A 3 —At the termination of every period of three years, calculated from the date of appointment until they attain the age of 45 years, and thereafter annually until the conclusion of their service.



Note: (l) The staff in categories A l, A 2 and A 3 should be sent for special medical examination in the interest of safety under the following circumstances unless they have been under the treatment of a Railway Medical Officer.



(a) Having undergone any treatment or operation for eye trouble irrespective of the duration of sickness.



(b) Absence from duty for a period in excess of 90 days.



(2) If any employee in medical category A has been periodically medically examined at any time within one year prior to his attaining the age of 45, his next medical examination should be held one year from the due date of the last medical examination and subsequent medical examination annually thereafter.



If, however, such an employee has been medically examined, at any time earlier, than one year prior to his attaining the age of 45, his next medical examination should be held on the date he attains the age of 45 and subsequent medical examination annually thereafter.




Ammendment: It was ammended in 1993 as below



Age Group PME Due



Age 00-45 every 4yrs



Age 45-55 every 2yrs



Age 55-60 every year
Details:-
As per Rly Bd's Guideline of Medical Exam issued vide LNo. 88/H/5/12 dated 24-01-1993

a) PME would be done at the termination of every period of 4 years from date of appointment / Initial medical Exam till the date of attainment of age of 45 years, every 2 years upto 55 years & there after annual till retirement.
b) Employees who has been periodically examined at any time within 2years prior to his attaining the age of 45years would be examined after 2years from the date of last PME & subsequent PME for every 2years upto 55years age.Of

NRMU 4 you
SMLokhande





6.1.2. Classes B-1 and B-2—On attaining the age of 45 years, and thereafter at the termination of every period of five years.