Explaining the VJD method - the alternative to the D/L rain rule being used in the TNPL

The ongoing T20 match in the Tamil Nadu Premier League between Dindigul Dragons and Madurai Super Giants has been truncated by rain, with both sides given 18 overs to bat. What makes this interesting is the fact that the more familiar Duckworth Lewis method is not being used to calculate the target score in the match, as cricket fans have grown used to seeing.

The TNPL is using the VJD method instead of the D/L system, a different method of calculating target scores in rain-truncated limited overs cricket matches, devised by a civil engineer from Kerala named V Jayadevan. This method was previously used in the Indian Cricket League, was considered for use in the fourth and fifth seasons of the IPL, and was even considered as an alternative to the DL method by the ICC.

In 2012, the ICC had thrown out Jayadevan’s proposed system, saying – “The committee unanimously agreed that there was no evidence of any significant flaws in the D/L method nor did the committee believe that any improvements could be offered by the VJD method."

The engineer had protested then that he had not been given a fair hearing. The DL method stuck on, to be modified to be made into a Duckworth-Lewis-Stern method, with the VJD system not being allowed into the international arena. However, there are some definite advantages that the VJD system can be said to have over the more common DLS method.

Why the VJD system is a more scientific method of calculating targets

For one thing, the VJD system takes into account the statistics from previous games. The DLS method does not take into account the reputation of sides or their recent form. While the DLS method has often been found to be overly mechanical, it is through these subtle modifications that the VJD method offers itself as a more human system.

The DLS method assumes that the scoring rate of teams continue to increase as the innings goes on, and fixes the target score accordingly. However, this is often found to be unjust as teams do not generally increase their strike rate in direct proportion to the number of overs gone by. As a result of this, there are often abrupt changes required in the projected score when the DLS system is followed.

The VJD system, to offer a more scientific alternative, divides the innings into phases. It assumes a high scoring rate in the first few overs, considering fielding restrictions, assumes a drop in the rate in the middle overs, and assumes another rise in the slog overs.

There are also different scoring patterns set for different scores. For scores below 100, the scoring approach is different than a score between 100 and 200, or between 200 and 300 and so on – consequently, different scoring patterns are used to find out the projected target.

Another advantage that the VJD method has over the DLS method in terms of having a more human way of calculating targets is that it considers two curves on the graph as opposed to the single curve on the DLS graph on which all calculations are made.

The justification for this is that a normal curve will represent the team’s scoring rate before the onset of rains, when they play with the assumption that a full quota of overs is available. A different ‘target curve’ is required to approximate the changed approach after the truncation of overs, as teams play with a changed approach as the number of overs left to play go down.

How projected targets vary in the two systems

(20 over match scores)

Team 1 Score – 150: DLS Target 93; VJD Target 91

Team 1 Score – 200: DLS Target 124; VJD Target 118

Team 1 Score – 250: DLS Target 154; VJD Target 142

Team 1 Score – 300: DLS Target 163; VJD Target 163

Team 1 Score – 350: DLS Target 174; VJD Target 182

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