The Effects of Additional Lines on a Football Field on Assistant Referees' Positioning and Offside Judgments

Abstract

Following the optical error hypothesis, information provided by extra lines across the width of a football (soccer) field (comparable to an American football field) could help assistant referees to judge offside. Therefore, we investigated whether extra lines across the width of a football field influence the positioning of assistant referees and their offside judgments. Eight expert assistant referees each judged potential offside situations played by several attackers and defenders on two different fields, one field with and one field without extra lines. The extra lines resulted in better positioning of the assistant referees but not in less incorrect decisions. A possible explanation for not finding better performance results in the number of incorrect decisions is that the assistant referees first have to learn to use the information provided by the additional lines for judging offside.