Before revision:  we propose a new metric which addresses failure cases of the off-road rate metric by penalizing trajectories that contain driving behavior that opposes the ascribed heading (flow direction) of a driving lane, and we show this metric to be differentiable and therefore suitable as an auxiliary loss function.
After revision:  we propose a new metric which addresses failure cases of the off-road rate metric by penalizing trajectories that oppose the ascribed heading (flow direction) of a driving lane, and we show this metric to be differentiable and therefore suitable as an auxiliary loss function.