A heavy human powered vehicle (HPV) that can drive 450lbs total combined weight up the steep hills in Vancouver will need at least two gears to climb the steep hills with a legal wattage. Read more: cycle tractor.
With 7500 rpm output for maximum momentum efficiency using a high voltage motor, you will need a lot more gear reduction (like 13:1 total) to keep it down to about 11-13mph [17-21kmh] on a 9% to 10% grade but even that would be quite a fast gear with Canadian legal power.
A retro-direct drive is a fast (high gear) in the forward direction and a slow (low gear) in the reverse.
Making a switch to reverse the motor: (see the middle of page 5): Epicyclic retro-direct 2 speed transmission.
The ring gear is attached to the output
shaft and the planet gears are stationary
on a plate with a one-way bearing
in the opposite direction.