Techniques are described herein for allowing one or more vehicles or radar systems in an environment to passively detect radar signals from other vehicles or other radar systems and determine spatial parameters of objects based on the passively received radar signals. A primary vehicle (or user equipment (UE) associated with the primary vehicle) may be configured to receive one or more radar signals from one or more secondary vehicles (or UEs associated with the secondary vehicles). The primary vehicle may be configured to determine one or more spatial parameters of the secondary vehicle based on the passively received radar signals. In some cases, the primary vehicle may receive an indication that identifies at least some communication resources to be used by the secondary vehicle to transmit the radar signals. The primary vehicle may determine one or more driving operations based on determining the spatial parameter.