Drafting = 3 mpg increase

Guys, I am a drag racer and when I was younger I raced at my local stock car track as well... There is no such thing as safe drafting on a public road, period. Quite frankly I am amazed that anybody here would choose to potentially waste the 9mpg ambulance, the electricity to charge the cell phones and radios on a 911 dispatch, the energy to produce sterilized medical supplies, and the money to pay an insurance deductable for the perceived improvement of 3 miles per gallon.

The bottom line is the road is filled with people who cannot parallel park, and who are reading newspapers, drinking coffee, driving after they had three beers, driving while arguing with their kids, driving for more than 10 hours straight, driving too fast or too slow for the conditions, driving while flipping radio stations, dvds, cds, talking on the cell phone, eating their fast food, and all the while worrying about what to get for dinner, whether they will be late to an appointment, and then these same people who have not been through drivers education in 20 years try to squeak through a red light, roll through a stop sign, are upset at the radar detector going off, and a host of other distractions.

There is no safe drafting, period. Safe drafting is right up there with military intelligence, progressive republican, fiscally responsible democrat, and the impoverished Catholic church. no offense to anyone (plus my wife is a Catholic), but drafting is not safe in any form as done by humans on a public way.

As a drag racer I guarentee that your reflexes (yes I mean all of you and myself included), are not as good as we think they are and we must take into account not only our own reflexes, but the body area that must respond to the reflex, plus the reaction time of the vehicle. I cannot stress this enough.

If my reaction time is half a second, it may take a tenth of a second for my foot to actually press a pedal to the floor, (like the brakes), and it may take the car an additional half second to respond to the command to stop, and that would be under perfect conditions. When i take into account that whatever is ahead of me is already doing something to cause my reaction in the first place, plus any drivers around me who are also reacting, plus the prospect of spilling my coffee or taking into account i may have been singing to the radio or focused on the instant fuel gauge, I become part of somebodys bumper.

In my uneducated but experienced opinion, people who draft should have fines steeper than those who speed, especially after reviewing how Montana had an increase in accidents after instituting speed limits and seeing how the Autobahn has a lower accident rate than we have on any highway here in the USA.

Please stop drafting.

 

Continuing factoids...

Many studies (Google it if you don't believe me) have shown that the average full-on brake time is a bit over a second in an emergency situation with a fully-alert driver, assuming nothing intercedes to bollix up the situation.

Prius stopping distances: 152 ft from 60 mph, 207 ft from 75 mph. Deceleration is about 17mph/sec.

My Suburban stopping distances: 162 ft from 60 mph, 220 ft from 75 mph. Deceleration is about 16mph/sec.

80000lb fully-loaded truck (hereafter "Truck"), drum brakes, no ABS: 292 ft from 60, 517 ft from 75. Deceleration is about 9mph/sec.

Truck with disc brakes on tractor, no ABS: 234 ft from 60, 371 ft from 75. Deceleration is about 11mph/sec.

Truck with disc/ABS: 194 ft from 60, 347 ft from 75. Deceleration is about 14mph/sec.

Truck tractors manufactured for sale in the U.S. after 31 March 2001 must be equipped with ABS, but not necessarily disc brakes. I couldn't find stats on drums with ABS, but it's obvious it'll be better than 9mph/sec.

Let's assume you're drafting a loaded truck at 75 mph, 110 fps, with a separation of two car lengths. In your Prius, that gives you a separation of 28 feet, a tad over a quarter second. A car pulls off of the shoulder, directly in front of the trucker you're drafting. He slams on his brakes, full on emergency stop. In the time it takes you to get your foot to the brake, he's slowed down by at least 9mph - you haven't slowed at all. You smack into his trailer at a speed differential of better than 9mph - your airbags deploy, blinding you and scaring hell out of you. He continues slowing at maximum deceleration (actually a bit more gradually now that you're part of his vehicle), and now you finally have your foot on the brake and start your own deceleration curve. Assuming you haven't underrun his trailer, and that you can disengage your wreck of a car from his now-slightly-scratched trailer, you have to pray you can see through the dust, bruises, and terror of airbag deployment, maintain control of your new wreck, and stop without killing yourself or anyone else. Hey, at least you get to be on the news, huh?

If you draft me in my Suburban, the speed differential will be better than 16mph. Chances are pretty good you'll knock us both out of control.

Exaggeration? Nope. I cut more corpses and live idiots than I care to think about out of destroyed cars after just such accidents, and worked accident scenes with awfully lucky idiots more times than that.

It is NEVER worth it. I'm through ranting about this - it's a bit of a sore spot. How 'bout those Miami Heat?

 

Here is something to put it into perspective... the one reason I do not draft is because I have seen 2 wrecks in the last 5 years where someone became a bumper sticker on the back of a semi. Not sure if they were drafting or not paying attention but it was not a pretty sight.

Remember, no matter how much you save it won't make a difference if you get in an accident. Yeah it is iffy but are you willing to take that chance.

 

<div class='quotetop'>QUOTE(DaveinOlyWA @ Jun 27 2006, 12:11 PM) [snapback]277431[/snapback]</div>

Splitting hairs here, but if the object in front of you runs into, let's say, a brick wall, the difference between the following distance and the impact distance becomes moot.

<div class='quotetop'>QUOTE(Tadashi @ Jun 27 2006, 05:07 PM) [snapback]277599[/snapback]</div>

Indeed. And my supplement to that argument is that it isn't your chance to take, nor is it anyone else's. Doing stupid things (and yes I'm using the term "stupid" properly) that increase the risk of getting someone else killed is simply unacceptable.

 

<div class='quotetop'>QUOTE(glenhead @ Jun 27 2006, 09:37 AM) [snapback]277411[/snapback]</div>

There's this Discovery Cube http://www.discoverycube.org/ in Santa Ana, CA that's great to just wander around or take kids to for a field trip.

They have this one exhibit that measures reaction time where you press a button to activate it, and then when you see the counter start (randomly) and lights flash you press the other button. Myself and the other, consistently get 0.20 seconds reaction time (unless it's wrong), but it's been consistent with a stop watch also. My friend gets 0.15 seconds reaction time and usually beats me in games such as "You Don't Know Jack". So my take is 0.40 seconds is pretty slow - what age group, and what else is not being described?

Also, I think you're taking 2-3 car lengths too literally because many could be meaning about 2-3 seconds. Also, trucks generally don't drive over 65mph, and more usually at 55mph, so braking distance relatively does not matter, just space for reaction and avoidance. But these days, especially in LA, you're be lucky to consistently even drive up to 65mph with the amount of existing traffic.

I rather see some beefing up of our crappy driver's license test (in the USA), and eliminating passing on the right.

 

<div class='quotetop'>QUOTE(NuShrike @ Jun 27 2006, 08:58 PM) [snapback]277777[/snapback]</div>

Yeah, I'd kind of like to keep the ability to legally pass on the right... too many farm implements on the highway around here.

 

I haven't doubled checked all of glenhead's numbers, but I believe them and that they're at least within an order of magnitude of correct if they aren't. He is right about 70 mph = ~103 feet/second. A Surbuban is 222.4 inches long putting your 1-2 SUV lengths at 18.5 to 37 feet. One car length is way too close at highway speeds and two is pretty marginal for any length of time.

As I stated earlier, I think it's silly and irresponsible to do this for even if it yielded a 50% improvement. Do you know how much it cost (the insurance company of the driver that hit me) to get a rear bumper cover repainted and replaced, lower rear spoiler replaced, impact abosrber replaced and some MINOR body damage repaired under the bumper cover on my Prius? It came out to >$1300 with towing. I still need to submit a receipt for the first tow and replacement HOV stickers adding another $85. This was from a woman clipping my rear bumper in parking lot at VERY low speeds.

If you got into a wreck on the highway due to drafting, the damage and medical expenses could FAR exceed the value of your car.

Click on the pictures at http://www.iihs.org/ratings/rating.aspx?id=641 to see what a Prius looks like after a 40 mph frontal offset crash.

 

<div class='quotetop'>QUOTE(NuShrike @ Jun 27 2006, 09:58 PM) [snapback]277777[/snapback]</div>

There is more than one reaction time involved. The driver and the vehicle must both react. Secondly, often we are talking about feet and not mouse/finger speed, and thrid we are usually not expecting to have to react so we must also figure out the approriate reaction prior to acting.

No offense intended but I can do better than .2 on those reaction times games to the point where I have "super reflexes'... Because I drag race I actually work on my reflexes daily. I know that my reactions in a one of a kind situation are really no better than anyone else. Sure I am usually more familiar with high speed issues and more experienced with responding to vehucle issues, but if I were three feet behind a truck that slammed on the brakes I am just as crashed as anyone else, especially if I have the iPod happening and a coffee going on.

 

<div class='quotetop'>QUOTE(tnthub @ Jun 28 2006, 05:35 AM) [snapback]277969[/snapback]</div>

That's fine.. your explanation makes more sense especially that feet are slower than hands.

<div class='quotetop'>QUOTE(tnthub @ Jun 28 2006, 05:35 AM) [snapback]277969[/snapback]</div>

Hyperboles make poor and unrealistic illustrations of the point. It's more likely the truck will jack-knife given such extreme examples, but considering accident statistics, one is more likely to be in an accident with another vehicle (such as a SUV) than a commercial truck.

So summary: don't do it, but it's safer than following a car or SUV, or being in a SUV (some).

 

too many valid points here that no real need to add anything else. other than the one claims a 3 mpg increase @70 mph drafting than @65 mph driving alone.

well, @ 60 mph, i see an 8 mpg gain. have no risk, am able to play with my GPS, VAIS, and my honey knowing full well that i have plenty of time for HER to warn me when i should pay attention to traffic

i know, it means sacrificing 10 minutes of my time by leaving early for everything i do. one reason why i love her, she hates being late. (first relationship ever that cared about being on time)

 

Remember your reaction time is because you are ready and waiting for it. In a vehicle you may not be expecting it (and it may not happen but once every 100 times), hence the 0.4 reaction time versus the 0.15.