Drivers process mandatory signs faster than prohibition signs at three-way intersections
Sergio Moreno-Ríos, a researcher at CIMCYC, is one of the authors of the article Signalling Three-Way Intersections: Is Redundancy Better Than Only Mandatory or Prohibitory Signs? published in Frontiers In Psychology journal. The paper reports a study that investigates what could be the best traffic signs to signal a three-way intersection based on the decision speed of the drivers.
At intersections, drivers need to infer which ways are allowed by interpreting mandatory and/or prohibitory traffic signs.Time and accuracy in this decision-making process are crucial factors to avoid accidents. Previous studies show that integrating information from prohibitory signs is generally more difficult than from mandatory signs.
In study 1, an experiment was carried out in which the volunteers were shown different situations at a three-way intersection, with a single traffic sign or with both types of signs (redundant condition).
In Study 2, a survey was carried out among the professionals responsible for signage to check whether the common practices are consistent with the experimental research. This survey included the main cities in Spain such as Madrid or Barcelona.
The results of study 1 showed that inferences with mandatory signs are faster than those with prohibition signs, and redundant information facilitates performance only with prohibition signs.
In study 2, the results suggest low levels of agreement among professionals. Some of them stated that they had no theoretical or empirical basis to follow a clear criterion. Despite the lack of agreement, prohibition signs are more widely used and in some cases double signs.
These results point to some recommendations to potentially facilitate and speed up the interpretation of road signs and the inferences drivers make from them, which could give them some extra time that could be crucial to process other important information and reduce the probability of accidents.
In conclusion, the most used signals, according to the study, were not the best for signaling because the fastest responses were obtained with obligation signals, and secondly with redundant signals.