But, Eric. You must look at the bigger picture, think of the SAFETY!!!
Your own personal travel cube will never get too close to the cube in front, it won't go too fast, it won't break the posted limits on any road. It will wait till the junction is absolutely 110% clear before proceeding, it won't get frustrated by the cube in front doing 40 in a 50 limit, man! it won't even overtake because that could cause a collision, (previously referred to as an accident) You will be wafted along in near silence, at a mind blowing 35 mph, by an ecologically friendly electric motor which will be computer controlled to maximize mileage (at the expense of performance of course) and your personal safety will be it's raison d'être at all times. Oh, I forgot, throughout your journey it will play soft, sweet muzak to soothe and relax you.
Ken.