[ShadeTreeMech]

Mech posed an interesting question regarding heavy car vs light car in hilly terrain, with the assumption that a heavier car has a higher kinetic energy going down a hill to recharge batteries, but then it would burn more going up hills.

Since I drive in hilly country nearly all the time, I have to say I would prefer a lighter car on any accounts, mainly because hills inevitably involve going around corners. Drving something heavy would certainly cause you to slow down more than a lighter nimbler car which you could drive around most corners at speed.

One big factor in car design that I see causes conflict is whether to have several vehicles for several tasks, or fewer cars that can fulfill all tasks. Minivans are rather large, however they fulfill nearly all tasks Joe Average would need from a car. But what about when he is just commuting to work? Well, a motorcycle has highest chance of making great economy, short of having an EV metro you conned Ben to make for you.

I currently have a minivan and a mid sized sedan, but there is a Geo Metro 4 door I've been drooling over lately for economy. I also have a derelict Explorer I need to get going for the rough stuff. If I were to buy the Metro (or similar car) and get the Explorer running, then buy a trailer for the Explorer to tow when needed, I'd have all my vehicle needs fulfilled. But that's a total of 4 cars for a 2 driver household!

How hard would it be to make a vehicle that can come with removeable passenger/freight modules to lengthen or shorten the vehicle as needed?