Hi Chris - there is a Voice Navigation option under Premium membership, although this is currently a BETA feature. I'm not sure how effective it would be for someone visually impaired though, as they would still need some degree of vision to use the app and respond to the spoken directions safely.
Hello PlotARoute
Is it possible to develop PlotARoute.com further by adding the feature of directions that are audible. The audible feature would enable the visually impaired to access the routes also.
Kind regards
C MacDonell
New Zealand