Why do we have a seeding system? The reason for the seeding system is to eliminate, as far as is possible, the chances of a faster driver being held up by a slower driver on a competitive stage.
How does it do this?
It does this by ascertaining the speeds of all drivers, relative to all other drivers, and ranking them in order of speed not on results. This is done on the basis of stage times set in the last three ARC events that a driver has competed in.
Simple in principle, but how is the co-efficient calculated? The mathematical process by which the seeding co-efficient is calculated, also known as the “Driver Performance Index” (DPI), is a complex one.
A “Stage Performance Index” (SPI) for all competitors for each competitive stage in an ARC event is calculated by dividing the fastest competitive stage time by the stage time of each driver. This will result in a value of less than 1, except that the SPI for the driver who recorded the fastest stage time will be 1. A driver who takes twice as long to complete a stage as did the driver who recorded the fastest stage time will have a SPI of 0.5000.
An “Event Performance Index” (EPI) for each competitor is then calculated from the SPIs. The EPI is the average of the “best two thirds” of his/her SPIs. By effectively discounting the worst third of a drivers SPIs the likelihood of an unrepresentative time where a driver might for example have been caught behind a slower vehicle or had a puncture are all but eliminated. This gives a truer indication of a driver’s actual speed.
An EPI will only be calculated from an event when a competitor has completed a minimum of six competitive stages to ensure that as far as is possible only representative data is used as a basis for determining seeding positions.
From the EPIs a Driver Performance Index is calculated which is the average of the best two of the last three EPIs.
The seeding system is not skewed by poor performances which are not typical of the driver as the worst 30% of his/her performances are discarded.
Driver Performance Indices are only valid for three years as of 2020, before returning to two years from 2023, and the driver is then removed from the current Seeding List. Should the driver later return to competition then their archived indices will be used to determine his seeding.
By using only a competitor’s last three events, the system is capable of reacting quickly to cases where, for example, a competitor upgrades his/her car and suddenly becomes much quicker.
It is not necessary for a driver to be a finisher in order to get an Event Performance Index. As long as they completed six competitive stages throughout the event, an EPI will be calculated. Seeding is based on ability to drive fast not on ability to nurse slow machinery through to the finish.