A method for calculating a collective perception message, CPM, information significance level, ISL, in a cooperative intelligent transport system, C-ITS, using a wireless communication channel for transmitting, receiving, processing and/or discarding a plurality of collective perception messages, CPMs, containing information about on-board sensors and/or objects detected by said on-board sensors within a traffic environment, said method comprising the steps of: calculating a collective perception message significance index, CSI, value for each CPM filled with object data of the objects detected within a field of view, FOV, of at least one sensor provided at an intelligent transport system station, ITS-S, or included in a shared message received from another ITS-S as being present in the communication range of the ITS-S; calculating the information significance level, ISL, on the channel based on the CSI values for all received CPMs; and sharing the calculated ISL with other ITS-Ss, wherein the significance index, SI, is calculated by a collective perception service, CPS, based on data obtained at a host intelligent transport system station, ITS-S, about a detected object, wherein such data include at least one of kinematics, novelty, time elapsed since last update, classification, confidence of detection, and/or based on the need of other ITS-Ss, and the information significance level, ISL, comprises determining a local information significance level, ISL_L_0, on the channel from the message significance index, CSI, values for all received CPMs as a local zero-hop value by averaging the CSI values of all received CPMs within a predetermined time interval. calculating a collective perception message significance index, CSI, value for each CPM filled with object data of the objects detected within a field of view, FOV, of at least one sensor provided at an intelligent transport system station, ITS-S, or included in a shared message received from another ITS-S as being present in the communication range of the ITS-S; calculating the information significance level, ISL, on the channel based on the CSI values for all received CPMs; and sharing the calculated ISL with other ITS-Ss, wherein the significance index, SI, is calculated by a collective perception service, CPS, based on data obtained at a host intelligent transport system station, ITS-S, about a detected object, wherein such data include at least one of kinematics, novelty, time elapsed since last update, classification, confidence of detection, and/or based on the need of other ITS-Ss, and the information significance level, ISL, comprises determining a local information significance level, ISL_L_0, on the channel from the message significance index, CSI, values for all received CPMs as a local zero-hop value by averaging the CSI values of all received CPMs within a predetermined time interval. the significance index, SI, is calculated by a collective perception service, CPS, based on data obtained at a host intelligent transport system station, ITS-S, about a detected object, wherein such data include at least one of kinematics, novelty, time elapsed since last update, classification, confidence of detection, and/or based on the need of other ITS-Ss, and the information significance level, ISL, comprises determining a local information significance level, ISL_L_0, on the channel from the message significance index, CSI, values for all received CPMs as a local zero-hop value by averaging the CSI values of all received CPMs within a predetermined time interval. <EOS>