Equally spaced drifts maximize the speed of one-dimensional random walks

Consider random walks in environments on ${\mathbb{Z}}$ composed of two types, $(p,1-p)$ and $(q,1-q)$, where $\frac{1}{2}<p<q<1$. Equally spaced drifts conjecture. An environment which maximizes the speed is given, up to some integer effect, by equally spaced drifts. The conjecture proposes the speed-maximizing arrangement for these two-point environments; the source does not state a resolution, so its status remains open.