I've noticed that the Smart is particularly suseptible to a kind of wake vortex effect from pick ups and larger SUVs especially when they're driving formation style just off the left rear of the car. I know it's people gawking,marveling or taking pictures with their cell phones. The problem I've noticed is that apparently it's disrupting the Smart's aerodynamics and causing noticible latitudinal oscillations proportional with velocity. It's probably there with all cars,but I think with a lightweight micro car it's just more noticible. Something to be aware of.
If you have the chance (safely,of course), get a couple of car lengths behind a semi trailer for a while and feel the draft effect. I followed a trailer for about 12 miles this morning on the Santa Ana freeway and was barely touching the accelerator pedal the entire time, even on slight upgrades. If you're not in any great rush,it's your ticket to hypermilageland.
BEAT CAL