If people wanted to travel 80km/h they could do so today. It is well known that going slower improves fuel efficiency. I'm asking for things like improved drivetrain efficiency and better aerodynamics.
If your 90% efficient drivetrain-tyre system uses 20 kWh per 100 km, then improving that to 95% efficient maybe reduces that to 17 kWh.
Pencils and javelins have lower drag coefficients than cars. Unfortunately people don't fit inside them. A javelin-shaped vehicle big enough to fit a person comfortably inside is a train.
or a cybertruck.