A method comprising: sensing, by a first user equipment (654a, 654b), UE, a signal transmitted by a second UE (654b, 654a) indicating a resource reservation for a shared channel for a sidelink, SL, transmission by the second UE (654b, 654a) and a priority associated with the SL transmission; determining, by the first UE (654a, 654b), a threshold based on a type of the SL transmission that the resource reservation is indicated for and the priority; and selecting, by the first UE (654a, 654b), a first resource in the shared channel to use for a SL transmission by the first UE (654a, 654b) based on the threshold, wherein the threshold specifies a signal power threshold, the method comprises measuring a signal power in the shared channel in respect of a second resource indicated in the resource reservation, and the selecting the first resource to use for the SL transmission by the first UE (654a, 654b) comprises excluding the second resource indicated in the resource reservation if the measured signal power exceeds the threshold, wherein the type of SL transmission that the resource reservation is indicated for is selected from a group that includes: (i) a blind SL retransmission of a previously transmitted transport block, TB; (ii) a future SL transmission of a second TB that is to follow transmission of a first, different, TB for which a resource reservation is also indicated in the signal transmitted by the second UE (654b, 654a) indicating the resource reservation for the second TB; and (iii) a feedback-based SL transmission of a TB that is a feedback-based version of a previously transmitted TB, wherein each of (i), (ii) and (iii) are associated with a different threshold. sensing, by a first user equipment (654a, 654b), UE, a signal transmitted by a second UE (654b, 654a) indicating a resource reservation for a shared channel for a sidelink, SL, transmission by the second UE (654b, 654a) and a priority associated with the SL transmission; determining, by the first UE (654a, 654b), a threshold based on a type of the SL transmission that the resource reservation is indicated for and the priority; and selecting, by the first UE (654a, 654b), a first resource in the shared channel to use for a SL transmission by the first UE (654a, 654b) based on the threshold, wherein the threshold specifies a signal power threshold, the method comprises measuring a signal power in the shared channel in respect of a second resource indicated in the resource reservation, and the selecting the first resource to use for the SL transmission by the first UE (654a, 654b) comprises excluding the second resource indicated in the resource reservation if the measured signal power exceeds the threshold, wherein the type of SL transmission that the resource reservation is indicated for is selected from a group that includes: (i) a blind SL retransmission of a previously transmitted transport block, TB; (ii) a future SL transmission of a second TB that is to follow transmission of a first, different, TB for which a resource reservation is also indicated in the signal transmitted by the second UE (654b, 654a) indicating the resource reservation for the second TB; and (iii) a feedback-based SL transmission of a TB that is a feedback-based version of a previously transmitted TB, wherein each of (i), (ii) and (iii) are associated with a different threshold.