On Mars as in the USA, vehicles are getting larger with time. You can see why: payload is tough to get into orbit, and expensive. I don't actually know what the postage for, say, the Mars Rovers' communications devices, but I bet it's larger than the total annual revenue of the postal services of a small country.
The first Mars rover, the 1997 Sojourner, was barely larger than a skateboard. The ones in the next mission in 2004, Spirit and Opportunity, were about the size of a bicycle, albeit one with six wheels and solar-panel wings. And Curiosity, which landed on Mars in 2012, is the size of a car, crammed with cool instrumentation for exploring the Martian surface.
The next one will be the size of a large SUV - electric, of course. There's a great side-by-side comparison of how things happen in the movie The Martian and how NASA's engineers are designing things for the #JourneyToMars project; one of them shows an exploration vehicle designed to house and move two people.