So, drafting big rigs scares me, but I noticed that if I follow just other normal cars (SUVs, sedans, whatever) at what would be probably considered close but not tailgating (hard to estimate the actual space, but I'd say 20-30% of other cars on the road are about at this spacing), I get a significant mileage increase. Like I normally get ~320-330 Wh/mi (usually drive 75 on the freeway, then slower on local streets of course), but while following other cars I was going anywhere from 75-85 mph just riding with the pack, and getting really low power usage, like maybe ~280 Wh/mi. And this didn't feel unsafe at all - certainly below the 2 second rule, so I guess it *is* unsafe, but it felt like normal "fast car pack spacing". And I would only do it if I could see traffic clearly over or through the windows of the car in front of me. But it was pretty significant - ~10% range increase. It was weird going 80-85 and seeing my power meter so low...
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Drafting big rigs saves a minimum of 10 percent range
- Thread starter artsci
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- Driving Dynamics Model S
Almost everyone knows drafting saves range just as most know it is dangerous. There are already threads on this anyway. And yes, I was serious. Sure, anytime you drive somewhere there is danger involved. Encouraging people to draft right on the bumper of a big rig just isn't smart. You are free to do it of course but have to live with the consequences and misjudgment causes to you, your family or other drivers. I'd say the same to those who refuse to wear seat belts or helmets when riding a motorcycle too.
Wrecks happen every minute and they always will. The goal should be to have fun and still encourage safe driving. If you slamming into the back of a rig at high speed only impacted you then that us your choice of course but it likely could impact others as well. Paperwork for truck driver, costs to society...etc
green1
Active Member
Yes, they react much faster. But nothing reacts fast enough in those cases. A properly designed ACC wouldn't let you draft that close as it would realize that a collision is imminent.I wonder how adaptive cruise control + drafting works.. Does the acc react faster than a human when the car/truck in front of you slams on their brakes?
And where do people keep coming up with a "2 second" rule? It's 3 seconds. not 1/2, not 1, not 2, a full 3. Anything less is dangerous, not just to you, but to everyone on the road around you.
bollar
Disgruntled Member
Because that's what some of us were taught. e.g. New York: Chapter 8: Defensive Driving | New York State DMV
And actually, the last driver's test I took was in North Carolina, a very long time ago. Also two seconds: http://www.ncdot.gov/download/dmv/handbooks_NCDL_English.pdf
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This is incorrect. I replaced my right rear tail light because of rock damage from a truck 7 car lengths ahead in another lane.
When the switch was first made from car lengths to seconds, two was the number. It's since been refined to three (or four in some cases), but that was something like fifteen years later.
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Distance only reduces the chances of rock damage, it doesn't eliminate it.
bollar
Disgruntled Member
But it really hasn't been changed -- at least not the way drivers are trained. Texas, also, refers to the two second rule: https://www.txdps.state.tx.us/internetforms/Forms/DL-7.pdf
The National Safety Council refers to the "three second plus" rule, but I could not find the details on their site. It's apparently covered in their defensive driving course available for purchase.
That maybe true for new fresh off the line equipment (although I have never heard of such a thing). I don't need some fancy governmental test to tell me which stops faster. I know from experience that even with the safety enhancements in the trucks today they still don't stop the same. It takes longer to stop a bobtail due to the rear tires skipping off the pavement under severe braking. Empty trailer helps keep the drives on the ground under severe braking but the tandem axles skip at that point under severe braking. A Fully loaded trailer avoids the skipping and stops the shortest distance due to the weight pushing and holding the suspension to the ground. The more the tires are on the ground the quicker it can stop. It's not brain surgery here. Ever wonder why some trailers start fishtailing under severe braking? It's due to them skipping off the pavement and the momentum pushes them sideways. That's why jackknifes are so common. If what you said was realistic then we'd only see jackknifes in in-climate weather but they occur most common in ideal conditions.
It's so hard to stay out of these discussions :smile:. As we've moved on from the drafting discussion ... I'd be happy to keep a 5, 6 or 7 second gap with the vehicle in front of me if I'm driving on open interstate with extremely low traffic. When I'm driving in traffic at speed here, leaving a gap of more than 2-3 car lengths means cars will continue to slip in front of you, constantly reducing the follow distance. Just the way it is. And this isn't a city driving issue, it's for long stretches on the East Coast. I can drive from Fredericksburg, VA to well north of New York City at 70+ mph in tight quarters. The exception would be if I wanted to camp in the right lane at precisely the speed limit.
Agreed. I get so annoyed with my wife's ACC when there is any kind of congestion. It follows far too far back for the conditions and you just end up with folks leap-frogging you, further pushing you back.
EarlyAdopter
Active Member
LOL. That test was done in 2011 using a 20 year old 1991 Volvo tractor!
Just be careful either way, loaded or unloaded, which it sounds very much like you are. And keep watching out for those pesky drafters. I'd hate to see you or anyone else lose their license on account of some driver trying to save a few bucks in gas or gain a few extra miles of range running up under the back of your trailer.
InTheShadows
Active Member
I learned 2 seconds when I got My license.
Who even follows that rule anyways. Here in the north east 2 seconds in traffic says "hey everyone, cut me off". Most people on the roads I drive are quite comfortable driving 70-75 mph with 2-3 car lengths following distance which is way less than 2 seconds. It might even be less than 1 second. Go to Baltimore, NYC, or Philly and it's 1-2 car lengths. ( That's not behind big rigs though.)
green1
Active Member
bollar
Disgruntled Member
Seems like maybe the six second rule is more appropriate up North:
Highway reopens after Prairies blizzard causes 100-car pile-up | National Post
Video: Fog blamed for 40-car pileup in Alberta - The Globe and Mail
Weather blamed for pileups that leave one dead, several injured
InTheShadows
Active Member
I was with our daughter last week on I80 and a pipeline truck (Frackers!) was going about the same speed as us, (75mph) and we ended up doing the 7 o'clock stalk for about a half mile because of the hills and he sped up a bit after we created the hill. My daughter made a comment on how his one trailer tire looked really tall and skinny. I noticed that it was bouncing on the road. I told her that it could blow, when they bounce like that they make a lot of heat.
Well about two miles later we hit a nice down hill and he really took off, I'd say he was going about 85 or so and 1/8th mile in front of us and it happened! His tire blew. The vaporized blowing that shot 4" chunks of rubber 40' in all directions. We had the pano and all windows wide open and we felt the shock wave. I was directly behind him in the right lane and I killed the cruise and went full regen and headed for the shoulder. My daughter then started crying because the explosion scared her so bad and she thought something happened to our car from the tire exploding when I started to pull over. (We didn't even reach the debris yet). I told her we were fine and I just did that as a precaution because an explosion like that can cause the truck to wreck or he could throw the big chunk of tire.
All I can say is I'm glad it didn't cut loose when we were in the 7 o'clock position or we would be needing some serious body work, possibly some new glass or worse in the hospital from rubber flying through our open windows.
Now that that story is done back to the topic.
That tire explosion would have been horrible in the 7 o'clock position or in some stunt man following distance at 6 o'clock. You never know when something like that is going to happen. Many consider that 7 o'clock position safe. I was just in it because that's where the cruise control put me.
You never know when something like that is going to happen. I see truck tires like that one probably almost monthly, I drive roughly 40k miles per year and most of that is on highways. I have only witnessed 3 big rig blowouts and all of them left me thankful I wasn't super close when it happened. I can't tell you how many passenger blowouts I have seen. (Want nightmares, go to your local walmart and start counting cars with the chords showing.) Plus the chunks of tire shards in the highway that could get kicked up. Bad news.
I used to be an evangelizing hyper miler. (I was getting 48 mpg out of our 98 protege, my wife was getting 33.) I had too many close calls. Including rigs brake checking me and hitting debris in purpose to kick it up at me. I would close in on the draft until all the buffetting was gone. This usually left me about 1-2 car lengths off the rig. Man, what was I thinking. It's just not worth it.
Well about two miles later we hit a nice down hill and he really took off, I'd say he was going about 85 or so and 1/8th mile in front of us and it happened! His tire blew. The vaporized blowing that shot 4" chunks of rubber 40' in all directions. We had the pano and all windows wide open and we felt the shock wave. I was directly behind him in the right lane and I killed the cruise and went full regen and headed for the shoulder. My daughter then started crying because the explosion scared her so bad and she thought something happened to our car from the tire exploding when I started to pull over. (We didn't even reach the debris yet). I told her we were fine and I just did that as a precaution because an explosion like that can cause the truck to wreck or he could throw the big chunk of tire.
All I can say is I'm glad it didn't cut loose when we were in the 7 o'clock position or we would be needing some serious body work, possibly some new glass or worse in the hospital from rubber flying through our open windows.
Now that that story is done back to the topic.
That tire explosion would have been horrible in the 7 o'clock position or in some stunt man following distance at 6 o'clock. You never know when something like that is going to happen. Many consider that 7 o'clock position safe. I was just in it because that's where the cruise control put me.
You never know when something like that is going to happen. I see truck tires like that one probably almost monthly, I drive roughly 40k miles per year and most of that is on highways. I have only witnessed 3 big rig blowouts and all of them left me thankful I wasn't super close when it happened. I can't tell you how many passenger blowouts I have seen. (Want nightmares, go to your local walmart and start counting cars with the chords showing.) Plus the chunks of tire shards in the highway that could get kicked up. Bad news.
I used to be an evangelizing hyper miler. (I was getting 48 mpg out of our 98 protege, my wife was getting 33.) I had too many close calls. Including rigs brake checking me and hitting debris in purpose to kick it up at me. I would close in on the draft until all the buffetting was gone. This usually left me about 1-2 car lengths off the rig. Man, what was I thinking. It's just not worth it.
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I have only drafted with intent once, taking a 180 mile drive home in winter, hit a storm with a 30mph headwind and with temps in the teens would not have made range without the draft, didnt like experience, the rig kept slowing down, braking, eventually pulled over practically to shake me loose. I made it home as only 50 miles of the drive was into the wind. Does make you realize the limits of the car without bundant charging, there is a planned SC on my route in 2015, if available, would have just stopped for safety range. That said, the benefits of drafting are very real, and magnified in that situation, I think I was getting almost 100wh/mi difference!
huntjo
Member
I follow that rule. Of course I'm a trauma surgeon, so like our friend Green1, I've seen what happens to those that don't.
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