Submitted by Da_Dokta t3_z79t64 in explainlikeimfive
someflow_ t1_iy5momt wrote
Reply to comment by Dayofsloths in ELI5 How do slipstreams work? by Da_Dokta
It's not necessarily true that there are only benefits at distances where you're "basically tailgating". For example this paper found a noticeable benefit for two tractor trailers even at 20 meters distance.
20 meters might be a little closer than "optimal safety", but in real life on busy highways many people are following that close behind or closer. This paper found the biggest benefit at 60 feet but even at 160 feet there were significant benefits.
common_sensei t1_iy5r5ix wrote
There's research being done to automate the process for large trucks so that they move together as a 'platoon', communicating with each other for semi-autonomous braking and accelerating. It would save a whole lot of fuel on long-haul drives.
bugi_ t1_iy5swrr wrote
Leave it to Americans to reinvent trains in a super complicated way.
yogert909 t1_iy75mr7 wrote
Semi-autonomous vehicles on existing roadways is way less expensive and less complicated than building completely new rail lines everywhere.
bugi_ t1_iy7fkbf wrote
How is it less complicated? We need new technology for that to happen. On the other hand we have trains right now. Tested and ready to go. There are all kinds of safety issues with having those trucks on public roads with other traffic which might mean they don't get approval any time soon.
yogert909 t1_iy8bprk wrote
Rail is complicated for different reasons. Technology isn’t the problem with rail. It’s the cost, getting the right of way, nimbyism, politics, environmental, and so on.
Have you ever seen a rail line built? They’ve been building a light rail line near my house since before I moved in 12 years ago and it’s not scheduled to finish for another 2 years. Funding and engineering went on for years before that.
Whatever new tech we need to get the trucks following each other will be done before this rail line. I think the technology is pretty close already. My wife’s 2016 Subaru has adaptive cruise control and lane assist which seems like enough to draft a semi.
Psilocybeazurescens1 t1_iy7l01y wrote
Yes, that's why we have tons of already existing semi autonomous vehicles with many more under construction as opposed to rail. Nobody ever in history has ever build rail and no one in their right mind would think to buil new lines
yogert909 t1_iy8aonq wrote
Woah there Tex. Calm down. It sounds like you’re thinking I’m saying something that I’m not. We can have both. And I really rather like traveling on light rail.
But it’s said there wil probably never be another heavy rail line built in the us because of the cost.
Dayofsloths t1_iy5o2ch wrote
Yeah for sure, I guess I drew a line between the "slipstream" and drafting.
The first vehicle is "breaking" the air, so there's less resistance to the following vehicles. This is also why cyclists and birds tend to flock.
I was thinking of this as two different things and addressed one part, but really it's all a combination of factors.
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