  We present an approach to analyzing the safety of asynchronous, independent,
non-deterministic, turn-to-bearing horizontal maneuvers for two vehicles.
Future turn rates, final bearings, and continuously varying ground speeds
throughout the encounter are unknown but restricted to known ranges. We develop
a library of formal proofs about turning kinematics, and apply the library to
create a formally verified timing computation. Additionally, we create a
technique that evaluates future collision possibilities that is based on waves
of position possibilities and relies on the timing computation. The result
either determines that the encounter will be collision-free, or computes a safe
overapproximation for when and where collisions may occur.
