Pavement and traction

[supton]

They have been doing a lot of paving in my neck of the woods lately, and a fair amount of grinding pavement down before paving back over. This leaves grooved pavement. I've never had a problem driving on it--makes a bit of noise, might pull a bit--but I've always wondered: how much does traction go down? a bit, none at all? What about wet vs dry?

 

[BISCUT]

Thank you for asking. I've often wondered the same! Interested to read the responses.

 

[AlaskaMike]

I'd be surprised if there have been any studies done on the friction of smooth asphalt vs asphalt that's been shaved down and in the process of being resurfaced.

I used to have a table showing the comparative frictions of different road surfaces, for the purpose of estimating vehicle speed based on the length of skid marks, probably buried in a box somewhere. I do recall that the friction of wet alphalt is far less than dry, smooth asphalt, but no real surprise there.

 

[PimTac]

My experience has been that traction goes out the window if it rains. For the past twenty years or so they have been doing that kind of paving overlay on the freeways and when it rained you could definitely feel the loss of road grip. They usually don’t have that surface exposed that way very long either.

In normal sunny weather it’s okay but they usually slow traffic down anyway. Maybe less contact Surface?

 

[OVERKILL]

My experience has been that traction goes out the window if it rains. For the past twenty years or so they have been doing that kind of paving overlay on the freeways and when it rained you could definitely feel the loss of road grip. They usually don’t have that surface exposed that way very long either.

In normal sunny weather it’s okay but they usually slow traffic down anyway. Maybe less contact Surface?

A big component of this is tires. The OE GY's on my wife's 1500 are actually quite decent on dry pavement, but they are scary in the wet. Contrarily, when I had my M5, the amount of traction the PSS's I had on it afforded in the rain was mind blowing. I've also found the Michelin LTX MS/2 to be significantly better in wet than many other tires on the same vehicle.

 

[supton]

My experience has been that traction goes out the window if it rains. For the past twenty years or so they have been doing that kind of paving overlay on the freeways and when it rained you could definitely feel the loss of road grip. They usually don’t have that surface exposed that way very long either.

In normal sunny weather it’s okay but they usually slow traffic down anyway. Maybe less contact Surface?

IME it can be a few months. Highly variable of course.

Trying to think, I think this morning there was a section where they shaved one half the side, leaving the crown as-is but shaving the passenger side. But I did not see any signs about being in a work zone, not in this particular area. Pretty sure I've seen plenty of miles of this stuff with plenty of traffic moving at typical speeds.

 

[Kestas]

In general, the less noise a road surface has, the less friction it has.

 

[tshephard]

As to the OP - I would bet traction increases, but wear much more so - like a file
Wet, probably less traction (still more than smooth), same increase in wear.
No real data, just experience!

 

[ABN_CBT_ENGR]

grooved pavement
how much does traction go down?
a bit, none at all?
What about wet vs dry?

Having done COF studies ( traction is a measurement type of COF), I seriously doubt you will ever see a legitimate one ( peer reviewed or certified by an individual or organization) addressing your key points because of the cost and potential liability of the published results.

Granted most of mine are on conveyors and drag links but fundamentally there's little difference between them and a tire/road traction event.

For example, for me to address that ( talking an official report with my stamp that makes a proclamation based on legitimate scientific techniques)

The results would only be valid for the specific car set ( establishes contact geometry, weight, angular acceleration etc.), the exact tire ( compound, size, inflation, tread pattern/depth, age)and stuff like incline, speed, angle etc.

Any one or all of those will significantly change the COF of a tire/road scenario.

Then stuff like grooving ( changes surface contact area and contact profile), type of asphalt ( surface asperities), wetness and all that.

That's a LOT of variables to capture and calculate to determine a ratio of traction for numerous considerations.

Even then the results would only be valid under test conditions with the test vehicle set up so results would vary against other vehicles.

That would be a lot of money and effort to get a study that had such a limited value and application.

 

[DGXR]

I would guess a slight loss in traction due to a disturbed pattern in the contact patch. Perhaps equally important would be inconsistent traction -- you can't just say "I now have 20% less traction all the time," it's not that simple. Even on new pavement the traction will be inconsistent due to rises/falls in paving surface (loading/unloading the suspension and tire), invisible spilled fluids, painted stripes/other markings, etc. I won't even get into snow, black ice, rain and other adverse conditions. Most people have no clue how to drive safely, let alone in bad conditions.

 

[ABN_CBT_ENGR]

I would guess a slight loss in traction due to a disturbed pattern in the contact patch. Perhaps equally important would be inconsistent traction -- you can't just say "I now have 20% less traction all the time," it's not that simple.

Then this traction change ( yeah its going to be a loss) is going to change hyperbolically because as the compound ages, changes surface texture and tread wears- the critical friction factors will change randomly along with it.

It will almost always be a moving number just based on the tire alone

 

[bbhero]

Well look at the repave jobs done at say Darlington or Atlanta or old Rockingham.... New pavement at those places greatly increased speeds... Then as the pavement aged speeds went down rather quickly. New pavement in those tracks typically led to an average increase of speed of 10-12 mph per lap... Which is a big, big difference.

Again once pavement aged those speeds went down a lot too. And new tires on a car out on either of those tracks would make a car faster by 10-13 mph per lap vs cars that had work hot tires with 40+ laps on those cars. You could make up a lot of time on fresh cool tires against your opponents if they stayed out on worn hot tires. A second to a second and a half a lap faster per lap done over say ten laps could easily mean gaining 10-14 seconds... This even came into play at North Wilkesboro when Brett Bodine came in and short pitted. He was a half a lap behind Dale Earnhardt Sr... Watching and looking at the time Brett came in and off pit road he ran about 4 minutes before Dale Earnhardt Sr came in. Which at North Wilkesboro a lap was run in 21+ seconds on old tires. So Brett had run 12 laps at a full second to a 1.5 second a lap faster pace than Dale Earnhardt Sr and Darrell Waltrip. So Brett had more than made up that half a lap distance by having much cooler and fresher tires than those other two leaders. Then the caution flag came out with Kenny Wallace's wreck going into turn 1. The caution car wrongly picked up Dale Earnhardt Sr has the leader. But Brett was actually in the lead. Dale Earnhardt Sr had pitted and so had Darrell Waltrip right before the caution flag had come out for Kenny's wreck. Some people thought Bret was on the tail of the lead lap but that just was not accurate. He had made up that half a lap distance behind Dale because he had run 12 laps aka he came in 4 minutes before Dale and Darrell had both hit pit road. He was truly in front of both of them. Now... Here's where things "went" wrong.... While NASCAR scoring was trying to figure out where everyone was in relation to the caution coming out... Brett Bodine hit pit road... Got 4 new fresh tires. Then NASCAR realized what had actually happened and put Brett being in 4th place the last car on the lead lap which he had been... To being in 1st place in front of Dale Earnhardt Sr and Darrell Waltrip.

And if you watch the race on youtube you will hear Benny Parsons say that he didn't understand why **** Trickle and others weren't still on the lead lap... Due to their scoring mistake they only had 4 cars on the lead lap... Right before that caution flag there were 10 cars still on the lead lap... Because there were a number of other cars that were on the lead lap prior to that caution flag and they had pitted before the leaders as well and they had solid pit stops as well. So that was the story behind that deal at North Wilkesboro. Fresh tires made up the distance. And because the scoring was off for awhile and had Brett Bodine at the end of the lead lap cars he came in and got four fresh tires while NASCAR was trying to figure out what really had happened. Then they actually corrected the mistake and put Brett up front in the lead.

 

[supton]

Then this traction change ( yeah its going to be a loss) is going to change hyperbolically because as the compound ages, changes surface texture and tread wears- the critical friction factors will change randomly along with it.

It will almost always be a moving number just based on the tire alone

Sure. Ok, I accept the notion that it can't be measured or stated quantitatively. But qualitatively? Sounds like it's between good pavement and pavement with snow on it, but much closer to the good pavement. So I should probably drive slower on the stuff, but not necessarily at the speeds I would drive on if it had snow on it. I should expect braking distances to go up, by how much no one knows.

Next time I'm out I should try a brake stand and see if I can get ABS to kick in. Hardly scientific I know, but it'd be interesting. I don't think my car can get ABS modulation on good bare pavement... well I've certainly never had it so far... but it'd be telling (to me) all the same.

 

[IndyIan]

Sure. Ok, I accept the notion that it can't be measured or stated quantitatively. But qualitatively? Sounds like it's between good pavement and pavement with snow on it, but much closer to the good pavement. So I should probably drive slower on the stuff, but not necessarily at the speeds I would drive on if it had snow on it. I should expect braking distances to go up, by how much no one knows.

Next time I'm out I should try a brake stand and see if I can get ABS to kick in. Hardly scientific I know, but it'd be interesting. I don't think my car can get ABS modulation on good bare pavement... well I've certainly never had it so far... but it'd be telling (to me) all the same.

I suspect once the dust blows out, the ground pavement will pretty much be the same for grip. Less surface contact but more mechanical grip due to the roughness. We have chip and tar on most of our back roads and I think its similar, at least while its new and the rocks are sharp, more mechanical grip and reduced contact patch. I'd like to hear how motorcycles do on grooved pavement? With narrower tires it could get interesting?

 

[ABN_CBT_ENGR]

Sure. Ok, I accept the notion that it can't be measured or stated quantitatively. But qualitatively? Sounds like it's between good pavement and pavement with snow on it, but much closer to the good pavement. So I should probably drive slower on the stuff, but not necessarily at the speeds I would drive on if it had snow on it. I should expect braking distances to go up, by how much no one knows.

Its not you

Its part of this "CSI" effect and i get it from clients all the time and often have to simply set them straight. ( then business types try to beat you over the head with it too)

They always want the simple 1 word answer. They want a number, a line, a "something" that's "right" and they can make a checklist around.

Then there is the false premise that "everything" can be solved for "x" and no matter how far the equation drifts from the formula its "still X" ( people don't want to accept responsibility for deviating from the process)

Things like you said ( qualitatively) that simply require critical thinking skills like "If it rains my tires are probably more likely to slide so I might be wise to go a tad slower" have been replaced by other things like "this tire has a 20% improvement in traction on wet pavement" ( with lots of fine print) when in reality it says nothing.

Then someone wants to sue because they didn't get that 20%- and so forth.

That's why we ( as a professional field in general) are so hesitant to answer questions or make statements in general now. They can come back and haunt us.

That's why I raised those points.