I have driven some miles on Interstate highways recently, and there are some areas where my tires make an annoying THWOK, THWOK, THWOK, THWOK sound. It’s clearly the pavement that causes this, but it’s not so clear what is different about some areas that cause this. Highway that has been overlaid with asphalt causes no extra noise whatsoever. Areas that are concrete laid in sections might or might not have this effect. Sometimes I hear a slight tick, tick, tick when my tires cross the section lines, but other times it can be a loud THWOK, THWOK, THWOK. The pavement doesn’t look any different - at least from the driver’s seat at 70 mph.
The only thing I can think of is that the sections of concrete could be uneven from one to the next, but then I really can’t believe that the highway builders could have made such a defect uniformly for mile after mile.
Specific locations are parts of I-57 south of Mt. Vernon, IL, and several miles of I-55 in Arkansas just south of the Missouri border - both north and southbound.
Has anyone else experienced this? Any ideas as to what causes it?
Sounds like the expansion joints on the highway. Very noticeable on concrete highways. As mentioned above particular tire characteristics can make it more noticeable.
The tick, tick, tick is just heard on highways with seams, not on seamless asphalt. As mentioned above, sometimes the tick turns into a THWOK. What is different about expansion joints from one section of the road to another?
The noise is from the concrete slab contraction joints. The slabs contract/expand during concrete cure, temperature and load variations. The joints are sealed to reduce water intrusions which is bad. You get freeze/thaw cycles in cold climates. Water can settle or wash away the substrate. On hot days the slabs expand pushing up the sealant material and you get the louder thwack sound. Cold weather give a slightly less annoying sound as the sealant has retracted.
On quieter concrete construction - they now use keyed construction joints on major highway and rehabilitation projects. For boring explanation and technical specs. see - http://www.fhwa.dot.gov/pavement/t504030.cfm
A lot of refurbed highways show what look like dog-bones acting like keys at the concrete joints.
There was an older thread regarding “what was this pattern in the roadway” that I can’t find - yet - with photos. I think it was out in Oregon or Washington state.
I’m familiar with this exact stretch of roadway. It’s the only place I’ve been in Arkansas, and it causes me to HATE the entire state. “What a miserable shithole,” I think every time I drive over this cursed stretch of road. Cruising along in Missouri, no problems; hit the AR border and “WHOMPWHOMPWHOMPWHOMPWHOMP” for ever and ever and ever…I seem to recall it’s worse in the right lane than the left lane. It’s the only time you’ll ever catch me just driving in the left lane when I’m not passing. Anyway:
I think it is probably the expansion joints, but I seem to remember noticing it feeling like my whole car’s going up and down, not bouncing exactly, but like each concrete section has a bulge or dip or something in it. So whatever’s going on there makes it worse than the normal “tick tick tick” or even “thump thump thump.” It seems like it was just poorly done, and they just said “well, whatever, there’s no holes in it so it stays.” I’ve driven that section at least once a year for, oh, 8 or 10 years now, and it’s been like that the whole time. Last time I was through there (7 or 8 months ago) I think there might have been some work going on in that area, but not sure if they’re redoing it.
EDIT: it’s usually November-ish when I’m making that drive, so it’s not warm temperatures expanding the sealant in this particular case.
When I drove a truck, it was often very noticeable on concrete roads, but on the same stretch in the car, I wouldn’t hear it much at all. I assume that the wheelbase, tyre size and resonant frequency of the suspension serve to magnify it when the slabs are a particular distance apart.