The freeways here in southern California are typically made of some sort of cement slabs. For some reason this invariably means that the freeway surface has a regular unevenness that is extremely annoying and wears out your suspension. Does anyone have more information the reasons for this construction techniques? Why don’t they adopt construction that results in smooth driving?
it’s called wear and tear. the same thing happens everywhere, there’s no special highway materials. i live in new york and the highways are always in terrible shape simply from the huge number of people using them – always under construction, always in crappy shape.
The OP’s use of “regular unevenness” sounds like a description of drainage grooves. To the best of my knowledge, all new concrete roads are built with undulating grooves going in the direction of travel. It can indeed be very annoying.
I know what the OP is talking about. Streets, roads, and freeways were constructed of concrete slabs with expansion joints. Although there isn’t regular freezing weather in SCal, water will still get into those joints and play havoc with the roadbed.
That results in the bumpety-bumpety-bumpety sensation when driving, almost giving the experience of driving along a railroad track.
Roadbuilding has changed considerably since then, but unfortunately, maintenance and replacement has really lagged behind need. Many of the freeways in SCal were constructed with a planned 30- to 40-year lifespan…and they’ve seen load increases far beyond anything predicted when originally built.
Concrete surfaces can only be reground once. Overlaying concrete with asphalt is an extremely temporary fix and wears unevenly.
Extensive freeway maintenance is horribly expensive, takes time, and inconveniences the traveling public.
~VOW
Yes, you get this every once in a while but I’d say the freeways in Southern California are pretty smooth, all things considered. They’re constantly in use and that makes maintenance very difficult. I don’t know what the OP is complaining about.
Do you have a particular stretch of freeway in mind? I can think of a couple of bad stretches here and there, but overall I’d say things are in pretty good shape in SoCal in comparison to other places in the U.S. I drive regularly. I wonder if you have an unlucky set of daily routes?
I think the grooves you are thinking of are for traction (Close-up photo of grooved pavement). Smooth concrete gets slick and slippery, especially when wet. The grooves (which look like they were made with a grass rake (photo) roughen the pavement and prevent cars from skidding all over the place in the rain.
However, I suspect that this post by VOW is more likely what the OP is talking about:
If you’re driving on CA consider yourself lucky. Here in the northeast the roads fall apart every year from the changing weather. Concrete is rarely used because of the repair costs. Sometimes the streets here get so bad there’s no original pavement left, it’s just all patches.
I recall when I was young the Baltimore-Washington Parkway was like what the OP described. Seems like they used extra large expansion joints.
Cement costs more but lasts longer, the price of cement and asphalt vary depending on the region. The decision to use asphalt or cement varies depending on if the highway department is trying to build on the cheap or spendi more money now to reduce future maintenence, the cost of materials in a given location, which company the highway department head is sleeping with or getting kickbacks from, the volume of traffic, the local climate.
The Midwest uses a lot of concrete since we’re a long ways from the major oil refiners but have plentiful cement and aggregate and have a harsh climate, out east I’ve seen a lot of asphalt where the opposite conditions are true.
They have to put expansion joints in or the cement would crack and the grooves to roughen up the surface. New techigue is to roughen the surface with weighted astroturf instead of a fine rake which produces a more irregular pattern and the road noise is a low growl instead of an annoying high pitched whine.
Indeed. Come on up to Illinois or Wisconsin, and I’ll show you what a worn, weather-beaten highway is really like. 
The ground can move under the roadway, especially if it is pounded while wet - the slabs sink in the mud, especially where the traffic pounds it as it comes of the previous slab. as a result, the slabs never lin up evenly after a few years.
You see a lot of contruction around the interstates where they are cutting a foot or two between the slabs, and adding a separte concrete chunk tied to the slabs with big metal rebar links to lessen this drop.
Also, the wheel dropping off or hitting the edge of a slab can cause spalling. Add in weathering effects, especially in the north, and the corners chip off (spalling). The nice square slab ends break off until there are serious pothole openings between the slabs.
One thing that can happen is that the concrete isn’t mixed quite right and flows a bit too much when they pour it. Then each section tends to be a bit thicker towards the downhill side. This results in a very annoying rhythmic humping kind of ride. I-79 down near the bottom of PA had this problem about 20 years ago (I have no idea if it is still like that or if it has been resurfaced since then).
This isn’t my area of expertise, but I am told that if you mix the concrete properly for the temperature when you are pouring and the slope of the slabs that you can minimize this to the point where it’s not noticeable when you are driving.
Another thing that can happen is called washboarding. This happens a lot on unpaved roads, but occurs on paved roads as well to some degree. What happens is that if there is a slight unevenness in the road (like the expansion joint between concrete slabs) then when your car’s tires hit it, it will cause your car to bounce up a bit. Then your car will naturally drop back down. Since most cars have fairly similar weights (roughly) they tend to bounce up and down in the same spot, so the place where the car’s weight drops back down gets a lot more wear than the road around it and gets compressed more. This makes a deeper bump, which causes cars to bounce more, doing more wear where they come down, making an even deeper bump, and so forth. It happens pretty quickly on unpaved roads. I’ve seen it happen fairly quickly on blacktop roads with semi trucks too, especially in areas where there is construction and the trucks have to slow down. You really just need one bump to start it. That bump causes the bump after it to be created, and the second bump causes the third, and so forth, until it extends quite a distance.
By the way, if you really want to complain about your roads, move to PA.
+1. You can tell you’ve crossed a border just from the feel of the road under your tires.
Photo of washboarding on a dirt road.
I’ve read that, if you drive at just the right speed on such a road, you can get the rate of passage over the bumps to match exactly with your suspension’s preferred resonant bouncing frequency, and then your car will roll perfectly smoothly over the bumps, and it will feel like you’re driving on a smooth road.
I’ve tried it a few times – never successfully. I have no idea, really, what speed I should be trying. Fairly slow? Fairly fast?
I thought Mythbusters did something like that. But I may be confusing it with the square tires thing, although it’s much the same.
They did the washboarding thing, too. The idea was, if you go fast enough, you don’t get affected as badly by the bumps. I can’t remember if it worked or not.
Wouldn’t you have to go about twice as fast as the regular traffic (so your wheels would bounce to the next crest rather than the next dip)? Sounds like a recipe for disaster to me.
It works. You either drive extremely slow or faster as you can stand to. If you drive near the resonance speed of the bumps and on a bad road it will shake the shit out of your vehicle. Not that driving very fast might or might not tear the hell out of the suspension eventually, but it is a smoother ride in many cases.
Yep, I’ve done it. Haul ass, get a smooth ride, but it’s because your tires aren’t making good contact with the road in the valleys between the bumps. Your traction is seriously compromised; combine this with your elevated speed, and you have a pretty dangerous situation.
Yep.
You only traction to slow down though. Well, that and turning 
I once road on a long dirt road with someone who could not be convinced to drive at ANY other speed than the one that matched the major bumps perfectly. I thought parts were going to start falling off the car.