Just occurred to me that while we mention bicycles as an extremely common form of transportation on space habs and in Martian cities, we've never published stats for them. I started to write some things down, but then realized that I don't understand the physics of bicycle frame geometry, brakes, etc. very well. Bicycle and rider have the same amount of inertial mass regardless of gravity, but reduced weight means the rider doesn't need to apply as much force to get the bike moving. So far, the main implication for frame design that I can think of is this: bicycles designed for use in low gravity would either need to have much more efficient rear brakes, or the rider would need to sit farther back from the front wheel. Physics geeks, please correct me if I'm wrong on this, but here's my reasoning so far: Bicycles get almost all of their braking power from the front brakes (about 90% is one figure I've heard). The rear brakes do contribute to slowing the bike down, but only fractionally. The rider's weight on the seat post & pedals prevents them from endo-ing over the handle bars when stopping. In low-G, the rider's weight is less. Slamming on the front brake could conceivably turn a bike designed for 1 G into a catapult. Also, rear braking sucks. If, like me, you've done many stupid things on a bicycle, you know that when stopping suddenly, rear braking (or having your rear wheel lock up due to a thrown chain on a fixed gear) can cause some pretty scary fishtailing. So, I'm thinking that transhumanity's low-G bikes either have a frame geometry that elongates the distance between seat post and front axle to prevent endos (which also changes handlebar geometry a lot), or (more crazily) they have power-assisted rear brakes combined with a fixed front wheel & rear wheel steering to prevent fishtailing. Either results in bicycle designs radically different from what we have now. Oh, and some interesting things I found while thinking about this: Offroading geeks debating Mars rover tires (the part about the tires leaving calibration marks in the Martian dust to corroborate wheel odometry is fascinating) NASA tested electric minibikes on the Vomit Comet for Lunar exploration, but they never made it to the Moon. Wonder how they worked? The design shown in this post might have had some problems if my speculations about frame geometry aren't wildly off base. This speculative post about mountain biking on Mars has some interesting things to say about getting traction in Martian terrain, but it doesn't seem to take on the issue of gravity much. Finally, I wonder if the geometry of a Pedersen-style bicycle would be less susceptible to the problems mentioned above.