Why should I care about "grooved pavement"?

There’s a roadsign on my commute that warns about “grooved pavement.” Why would I care about that? I can understand if it made the road less safe somehow, but I can think of why that would be - the grooves aren’t so deep and trecherous that my car is violently thrown to one side - in fact, I notice no difference at all when I drive over them, other than my tires making a small amount of more noise. It’s not like I read it, then grip the wheel and prepare myself for some dangerous hazard. If it were raining, the grooves would actually help, right? And as far as larger trucks are concerned, wouldn’t the weight of them and the size of the tires make it less of a concern?

I can’t think of why grooved pavement would be so dangerous as to warrant an official warning sign.

It is dangerous for bicycles with narrow wheels, of a similar size to the grooves in the pavement.

You would care if you were on a motorcycle. :slight_smile:

Your car behaves somewhat differently on grooved pavement than on smooth – not dangerously so, but sufficiently that the forewarning of the signs is useful in alerting you to pay attention to the slightly different “road feel.”

braking performance is worse on grooved pavement. You need to allow a little more distance between yourself and the car in front of you.

The sign can also serve simply as a warning that the feel of the pavement is about to change abruptly, so you aren’t startled, or don’t think it’s something with your car.

I am. :slight_smile: No difference whatsoever. The grooves are maybe a half-inch wide. The braking thing and the “don’t be startled” thing makes sense, I guess. Seems a little unnecessary to warn me about that, and not warn me about other more serious stuff. Meh.

It really depends which way the grooves go. If they are perpendicular to your line of travel they don’t make much difference. If they are somewhat close to you line of travel they can be tricky to ride on.

They cause no real steering problems if you are running with the grooves, but trying to turn can be different, plus the aforementioned braking distance problem. Same amount of tread, half the roadway surface it is in contact with.

Rain grooves parallel to the road can be treacherous to a motorcycle. I’ve had it grab a front wheel, shaking it side to side, scaring the bejeebers out of me just riding in a straight line, never mind turning or braking.

My experience with taking grooved pavement on a motorcycle (that is, grooved in the direction that I’m travelling) is that it produces a sort of “floating” effect. A little hard to describe, but it feels sort of like the tires have lost side-to-side traction, and are free to slide out from under you.

I don’t know if it’s literally true, or if it’s just an illusion. But it can be quite startling, to the point of making your heart jump, and I’m glad when they give some warning.

Ay, there’s the rub. They are perpendicular.

The perpendicular grooves off the side of the highway make a big difference - makes a godawful startling noise when you run over them, which is precisely the point, the grooves are there to tell you that you aren’t paying attention (or have started to doze off) and are drifting off the side of the road.

I actually had a conversation with a friend about this recently. Grooved pavement itself isn’t that dangerous, though it does have a tendancy to keep a tire moving in the direction of the groove (more noticeable on a motorcycle, as noted). The thing with the signs is that in many areas of the country it’s a special case rather than the norm.

In relatively dry climates it can go long enough without precipitation that oil builds up on the surface of the road, so when it does rain it becomes very slick and dangerous. The pavement is always grooved to keep the surface clear. I think this is what was meant earlier by “rain grooves”.

Where I’ve mostly seen the signs is around the east coast, and always in conjunction with road work. For whatever reason they groove the surface temporarily, but let people drive on the parts they aren’t finishing off at the moment. Since it’s not normal driving conditions they have to sign it. Notice, particularly, that the signs are on an orange background to denote road work.

I was going down a highway in Cleveland (Jennings freeway, for all who care), hit some grooved pavement in my 2004 Escape and nearly sailed right into the wall on a turn. Had to slow down to about 45 to regain very comfortable traction.

Then again I am quite suspicious of my tires to begin with…

If you’re unlucky enough to have tires with treads about the same distance apart as the grooves, they can “grab” your wheels. Not fun.

My 4X4 tires will get grabbed by such grooves, but only slightly. If I’m not really holding the wheel and don’t notice grooves coming up, I might get pulled a few inches to one side over a few truck lengths. No big deal if I’m in the middle of my lane, but if I was right near the edge, AND not paying attention AND not holding the wheel tightly enough, I could possibly bump into the car beside me. Drive properly however, and there’s no effect other than the bump on the way in and out.

In a former life I did public relations for a state highway administration, and our “grooved pavement” signs were mostly to keep people from being startled when the road suddenly sounded different. I don’t believe there was much (if any) inherent danger, even to bikers, but it could really catch people off guard. Trust me, you don’t want some of the people out there to be caught off guard while they are driving. :eek:

One thing I learned was to never underestimate the capacity of the general public to freak out about their cars: you would be amazed (well, maybe not) at the number of people who would drive on grooved pavement and think that “our” road had somehow damaged their tires/wheels/axles/etc. My office’s number was on the “we’re improving to keep you moving” signs, and people would call all of the time wanting the state to reimburse them for this or that. Luckily, we routed those calls to another agency. :smiley:

Also, “grooved pavement” signs only came in one flavor: there weren’t signs for “sort of” grooved pavement or “really” grooved pavement or “we hope you have new shocks” grooved pavement. Everyone got the same sign, regardless of how noticeable the grooved pavement was likely to be.

And now, the nominees for the most mentions of “grooved pavement” in a post… :wink:

We might be talking about a few different things here.

  1. In California, major freeways were once built very often out of portland cement concrete (PCC); increased durability, especially for the heavier and more frequent truck loads that might expected on such roads. PCC pavement does have it’s own minor problems; for one thing, it tends to “polish” after long-term use. The grooves are intended to increase tire friction to compensate.

(Yes, Southern California is notorious for the first-rain-of-the-season problem, where the roads then get especially slick from the crankcase drippings washing off the roadway. It’s also a problem because every other driver than me is an utter idiot :smiley: , especially during rainstorms. When we have them. IIRC.)

Anyhow, I don’t think this is where you’d find the ‘grooved pavement’ warnings - most ALL SoCal freeways are grooved now, I think, and it is a pretty ordinary thing, so there’s no point in warning anyone.

  1. The rumble strips are installed mostly on cross-country highways, and they’re GOOD. But I don’t think that’s where you’d find grooved pavement warnings, since the point is that under ordinary circumstances, no one is supposed to drive on them.

  2. This is a hunch, but I think there’s one other thing going on here: the ‘grooved’ pavement may be where the construction crews have milled off some pavement in preparation for constructing a new blacktop overlay. (Several possible reasons: remove pavement high spots; remove some areas of pavement damage; but mostly to allow a clean “join” to adjacent pavment.)

It’s a little bit of an, er, misnomer, there: the pavement isn’t grooved as such, but it is awfully rough. I imagine they call it ‘grooved’ pavement because ‘milled pavement’ or ‘grinded pavment’ (‘ground pavement’?) or anything else would just leave drivers scratching their heads even more, and this at a time when the basic message is, “Heads Up!” As noted, it really is meant to be a temporary construction thing.

It means you are supposed to hum or sing the 59th Street Bridge Song.