[johnunit]

I'd hate to be the one trying to get over two lanes stuck next to electronically-connected tractor trailers. Sounds like a nightmare for the traffic around them.


But I do agree with the general premise that there are many situations where you follow closer than a usual hypermiler truck draft distance/time gap. The point about trucks not being able to slow down as quickly is one I've made before too.

Theoretical situation:

I'm following another Prius in my Prius with a 1 second gap. He slams on his brakes, full impending lockup/ABS. I have less than one second to react if I want to avoid hitting him (and can't simply swerve to another lane). This assumes he will be coming to a full stop.

If I'm following a truck that takes potentially 3-4 times as long to stop as my car, at the same distance, my reaction time to his emergency braking is longer. I don't know the math of it, but in my head it's significant. I'd probably have well over 2 seconds to react and transition to full-effort braking and not hit him, assuming he comes to a complete stop in front of me.


If anyone is having trouble visualising this in terms of braking, perhaps thinking of it in terms of acceleration is easier. Think of how much more time you'd have to react to a slower-accelerating vehicle accelerating behind you at full throttle compared to a car that could accelerate as fast as your car. From a distance at which a car with the same acceleration potential as yours would only need a 1 or 2 second jump on you to eventually catch you, a tractor trailer would need a lot longer. Of course the difference is larger between a semi and passenger car in accelerating than braking, but the theory is similar.