A computer includes a processor and a memory, the memory storing instructions executable by the processor to determine at least one of: a brake threat number of a host vehicle, a brake threat number of a target vehicle, a steering threat number, or an acceleration threat number and to actuate the host vehicle to change at least one of direction or speed based on at least one of the threat numbers. The brake threat number of the host vehicle is based on a predicted lateral distance between the host vehicle and the target vehicle. The brake threat number of the target vehicle is based on a velocity of the target vehicle adjusted by an acceleration of the target vehicle and an actuation time of a brake. The steering threat number is a lateral acceleration being a predicted lateral distance adjusted by an actuation time of a steering component. The acceleration threat number is based on a predicted lateral offset adjusted by a predicted heading angle of the host vehicle.