Skybus Experiment-accident

Post accident of a freak nature during an experimenatal run, the system was certified following Railway Act provisions, and tested to obtain dynamic test results, reported here.   

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Bojji Rajaram   


Greetings- our country is caught in the web of ignorance of "experts" and procedure bound bureaucrats without understanding the spirit behind the rules, and create invariably, day in day out a "Draupadi Syndrome".  Our country deserves better than applauding the wealth robbers of our country as they are honoured by the foreign country getting maximum benefit of contracts!
Infrastrucutre can be created without tears and without impoverishing our posterity- if we use our intellectual capital and get out of mental servility.

Then the question of Skybus technology- is it a technology development project or an assembly of exisitng technologies?

Dr Indiresan Committee considerd the Skybus as technology development project- but actually if Skybus is a technology development project then every metro rail becomes technology development project! There is no new technology which is not already used and tested in railways, in factories or in other industries-it is actually the same railway technology at core- configured differently, the different configuration tested for safety!

There are some who merely cite an accident which occured during experiments of an uncertified system, to cry foul of Skybus.

Here is the accident inquiry report results, and after the accident the system was put thrugh normal railway system of certification to conduct dynamic safety trials, which were completed successfully. 

KRCL Accident Report




I have gone through the report.

The cause is identified as severe skidding of the sky bus system - but on rail no �skid marks� are observed. The marks that are mentioned here are what we normally observe in Railways, when wheel is jammed and �skid marks� appear in longitudinal direction on rail top in dry conditions. In this case, the thin film lubrication of water and grease has caused lateral skidding forces to swerve, occur as it happens on a road with oil and water mixture, would cause a truck to swerve when steering is turned. Severe rotational forces occur turning the
trucks even by 180°. The Sky Bus too in this case seems to have swerved /skidded as it tried to change direction on the entry of curve � with the presence of water and grease on top of rail.

By Physics, the coach should not have hit the column, even at the speed of 50 kmph because by design enough clearances are provided for centrifugal action.

But the coach has hit. Hence we do not have any other explanation other than, what has been brought out.

Similarly, evidence points to pushing of grease in longitude direction, in the direction of motion, which the Committee while recording evidence felt, could be because of application of brakes. But again this is in contradiction to evidence that the brake blocks were found in released condition and did not apply. The explanation, again can be that the skidding and swerving action of the bogies could have caused the movement of grease too.

In the first run of normal mode, there was no problem with grease etc. But why in the second run the swerving/ skid occurred ?

It is a matter of fact that there was no drizzle in the first run. In the second run drizzle caused addition of water to grease. Also in manual run, as man perceives, the speed control was exercised much earlier and electrical braking was continuously available. Perhaps with same electrical braking available in second run, the speed could have been controlled by the time curve was reached.

It is a matter of concern that grease has appeared on rail top, inspite of the entire rail top having been cleaned up 10 days earlier. All concerned staff have denied doing any thing to do with presence of the grease.

Way Forward :

  • Mechanical Brakes :

    Failure of mechanical brakes is a serious concern. With primary dependence on very superior electrical regenerative braking, the mechanical braking, got a short shrift in checking and making sure of the same.

    We shall provide a totally independent mechanical brake with parallel and independent controls and redundancy too.

  • Manual emergency stop in Auto-mode :

    In Automated systems, the manual intervention can queer the pitch � Had the operation of emergency button to abort experiment been delayed by a few seconds, the electrical braking system would have automatically taken over and covered the error of 50 m. in distance measurement which occurred due to slip of wheels. 150 m. extra distance is available to cover this type of mistake in distance measurement. However, error of judgement can occur when panic may occur. Design of emergency switch should be such that, instead of cutting off power in one go, a 5 second delayed action should be planned (as done in Reactor Management) during which period, emergency electrical braking should be applied and then only follow with the mechanical braking.

  • Curvature & grease:

    For commercial implementation, we shall avoid the curvature of 100 m., even though permissible, where one needs greasing the rail gauge face. Sky Bus can as well avail of 20 m. radius of turning, by using its traverser. Hence, we shall not adopt curvatures of track sharper than 250 m. But in cities we have flexibility to adopt even 20 m. radius curvature using traverser.

  • Auto-mode:

    For implementing the commercial automatic mode, the due processes of checking through �CENELEC Standards and certification will be necessary and one should avoid manual interventions when automode is in operation. Through the same automode, the emergency procedure has to be implemented using electrical braking first, then use the mechanical brakes.

  • Security � Commercially sensitive project :

    Security in the area has been now tightened and in commercially sensitive project entry and exit has to be strictly controlled.

    Positive points which emerged in this unfortunate accident

  • It is important to note that inspite of such impact forces, the people inside the coach were not crushed to death due to coach collapsing / capsizing. They survived the crash.
  • The suspenders did not fail, only got bent, but held positively the coach suspended, and so did not fall down on to the ground. This is as per our expectations.
  • The wheels did not derail but remained on track which is a positive point and again design has proven right.
  • So unlike in a conventional railway system, Sky Bus proved to be safer in disaster.

  • In summary before restart the following is to be ensured :

    1. The mechanical braking systems provided with additional redundancy.
    2. First electrical braking takes place before any emergency mechanical brakes are applied for control.
    3. Only manual mode running to be implemented, while the auto-driving devices are in background, effective to implement braking rather than drive, acting as ACD � an additional safety lever.
    4. Signalled train control system to be used in the first phase trials and will graduate to driverless system over six months � which is as per original plans.
    5. Our goal is to make Sky Bus fit to be certified like a normal rail line, with signal interlocking standards prevailing on Indian Railway for public carriage of passengers and similar to existing suburban Railways.

    B. Rajaram
    Managing Director/KRCL
    & Accepting Authority

     Certified to standard norms under Railway Act. the dynamic trials were conducted satisfacorioy, after implementing manual driving following line of sight signalling.


    Post Accident Safety Trials- results