Abstract: Among other things, techniques are described for checking the safety of proposed trajectories of a vehicle. In one aspect, at least one processor of a vehicle identifies a proposed trajectory of the vehicle. The processor determines a predicted trajectory of an object external to the vehicle. The processor obtains a velocity of the vehicle and predicts, based on the proposed trajectory and velocity of the vehicle and the predicted trajectory of the object, a likelihood of collision between the vehicle and the object. In response to predicting the likelihood of collision, the processor determines a change to a parameter of the proposed trajectory of the vehicle, and adjusts the proposed trajectory based on the change to the parameter.