Certain aspects of the present disclosure provide techniques for collision mitigation in sidelink. A method that may be performed by a user equipment (UE) includes measuring channel busy ratio (CBR), estimating a number of UEs using the channel, estimating a congestion level based on the CBR and the estimated number of UEs. A method that may be performed by a sidelink UE includes determining a semi-persistent scheduling (SPS) resource reservation including first subframes, determining second subframes for generated packet transmission, determining to skip transmission in the second subframes, listening during the second subframes for another sidelink UE’s transmission, and determining whether to reselect resources. Another method includes listening during a first subframe for another sidelink UE’s transmission, detecting the transmission collides with a scheduled transmission resource for the sidelink UE based on an amount of frequency resource overlap, and determining to reselect resources.