One major issue with transportation in the Martian environment is the extremely abrasive dust and the sharp rocks. Pretty much every rover has had the issue that the wheels deteriorate very quickly and dust gets into every nook and cranny, eventuelly destroying important movement-related mechanisms. As to their movement speed, that's mostly down to the movement being manually commanded and with the light delay of about 20 mins (one-way), you can only command the rover to go so far before involuntarily hitting an object.
Mistletoe|3 months ago
keyringlight|3 months ago
adrianN|3 months ago
pfdietz|3 months ago