Safety Factor

What is Safety Factor?

    Safety Factor is the extend to which system has ability to stay functioning amid problems.

Safety Factor vs Contigency Plan

    When designing a system, one must consider a Safety Factor. Its something other than Contingency Plan. Safety Factor is supposed to work automatically, parts falling place to replace disabled parts, ideally having no change in apparent behavior of system. Contingency Plan requires human intervention.

Explanation of Safety Factor

    A Safety Factor of 1.25 means that 20% of the total resources are extra, i.e. not immediately needed and 80% of the resources cover all of the immediate needs. Then if some of the units in resources break, the extra ones take their place, keeping the whole system working at same level of output.

    Resources can be people, machines, rolling money, buildings etc.

Quantity of Safety Factor

    In quran, God ordered us to prepare for war against non-believers and have twice as much preparation as is needed for visible enemies because there are non-visible enemies too.

    God Himself gave us two eyes when only one is needed, two hands when only one is needed, two legs when only one is needed and so on.

    Therefore, the optimum Safety Factor is 2.

    Half of the resources must be kept idle most of the time to be used only when working units are disabled.

Strategies of Keeping a Safety Factor

    Its better to not keep one half totally idle for all the time when there is no trouble. Either the resources are kept in rolling, with one half resting while other is working, or both halves are kept in working but only at half the capacity. For example in case of people its good to have the rolling strategy, in case of machines its good to have working at half capacity strategy.

What is and what is not Safety Factor

    If a country has two sea-ports, and both of them are needed for proper working of country's economics. For example, one port provide trade to half of the country and the other to the other half of the country, and no sea-port can provide trade for the whole country, then a Safety Factor of 2 means 4 sea-ports.

    In time of war, usually generals never commit all of the soldiers present at field to war. A reserve is always kept. This reserve is something where fighting units are supposed to fall back in case of a retreat. The reserve sits idle, remain fresh and it called at battlefield only when extremely necessary, such as when a front is facing unexpectedly large number of enemy troops or when enemy is using a tactic or weapon not planned for.


    The key is to realistically estimate what is necessary. Often commanders (be it generals, officers or managers) think what is reserve which is not reserve but is needed in normal working of the system. In these situations the reserve falls to 25% of total resources. Keeping this level of reserve is dangerous, its not strong enough to handle most of the problems, therefore in face of situation the whole thing collapse, even though the reserves are kept and paid for all the time. Then commanders think that keeping reserve is wrong strategy and decide to not keep any reserve at all.

    A lots of examples can be given for over-estimating reserves. In a battlefield, certain units have to stay behind to guard the camp, the hospital, equipment and materials. This is not reserve, the guards are needed for normal working of the system. Reserve is something that has no immediate duty and has nothing to do in normal times. Reserve also have to be large enough to provide not just for the fighting units but also for guards. The people working in hospital are similarly not reserve.

    Another example is a guard at a bank. Since most of the time, that is when there are no robbers at or near the bank, the guard sit idle, some managers think this as waste of resources and start giving peon level work to guards. The guard may be asked to post letters, fetch lunch for staff, even clean the manager's car. This is very dangerous. What if robbers come when guard is standing in a line at a post office waiting for his turn to post a letter?

    Another example is engagement of a country's military in running steel mills, electricity production companies or even railways of a country in peace time. Unless these companies are doing any military work, no armed forces person should be assigned to any of it.

    The commanders must clearly understand, without any vagueness, doubt or fuzziness, that certain resources must be kept idle, to be used only in times of crisis. There is a thing called too-efficient.

Where Safety Factor is Needed?

    I advocated a Safety Factor of 2, which I explained as keeping half of the resources idle. Do that means that we must always pay for double the staff than needed? No. Only critical resources must have a Safety Factor of 2, not all the resources.

    Safety Factor is needed for critical resources only, not for all resources. A critical resource is a resource that is mission-saving or life-saving, a thing which we cannot live without.

    Another way of understanding critical resource is that, a critical resource is one whose size must remain unaffected as system shrinks.

    Water supply in your house is a critical resource. You must have an in-house water tank, such as one in toilet or kitchen other than the overhead tank at the roof. Entire military is a critical resource.

    Managers are not critical resource. As company's size shrinks, its number of managers must also shrink accordingly. Same goes for sales staff.

    A commander must be able to distinguish between fats and meat. Fat is dispensible, can and should be shrinked in times of crisis, but meat must never be shrinked.

    Engines in an aircraft is critical, number of passenger seats is not. Pilot is critical, air hostess is not, passengers are not. In a sinking boat its ok to let go some of the passengers, but its not ok to let go the sailor, the man who rows the boat.

    All in all, the critical resource must never be more than 25% of the total number of resources in system. Keeping an extra 25% raises cost 25% if cost of keeping resources is same for all resources. Since critical resources are more expensive to keep, per unit, than non-critical resources, examples being pilots paid more than air hostess and military paid more than teachers, assuming a difference of two times, the cost of resiliency is 50%.