Sometimes that works too well, which is even more dangerous than traffic flowing briskly. I've seen I-80 flowing at 65-70mph all of a sudden hit a wall of traffic. I was on my motorcycle and worried about unattentive drivers slamming up against me. Traffic was intense. 20 minutes of bumper to bumper crawling where I had to keep both feet on the ground so my bike wouldn't fall over. That slow. I thought there must have been a huge pileup with all but a lane or perhaps just the margin open. Nope. Just a cop car on the side of the road. Once we got passed it, back to 65-70mph.
unattentive = inattentive
*sigh*
And of course the oblivious asshat in the cop car doesn't come to the conclusion that he's a major safety threat to everyone on the road and should drive away.