Rt. 83 in Maryland, a feceral highway, is a two lane limited acces highway that has been undergoing peculiar road work for the last several months. Every friday thru sunday one lane is closed and they are digging up rectangles of roadway, and then replacing them. Sometimes there will be as many as 15 of these rectangles in a single mile, other times only one or two per mile. The road they are tearing up appeared in good condition prior to the repairs. I have seen long stretches of road replaced, but these isolated rectanges, some very close to each other, is something I have never enountered before. Any idea what they are doing. It seems like it would be faster and probably even cheaper to just do the whole stretch of road.
They might be testing new construction techniques and/or materials?
I don’t think so. As I drive past each hole seems to look the same, and it’s been going on for months. They dig down to the gravel subsurface and then fill it back in again. They don’t seem to be digging deep enough to reach any crossing utilities, and anyway, they are digging way to many holes for that.
Maybe some kind of testing has revealed faults in the road surface that aren’t really visible to the naked or untrained eye.
I once lived in an apartment complex with a highly faulted concrete parking lot. Potholes would appear overnight after a heavy rain. One morning a patch of parking lot seemed fine … 24 hours and a few inches of rain later, a 4-inch deep crater would appear.
That’s probably it.
Viewed from a light plane, you will see many roads that are built crossing swaths of bright green. These are shallows of not-quite-streams that carry runoff diring the rainy season and are overgrown with grass the rest of the time. They are subject to stress during heavy rains.
This is low, I know, but I just wanted to comment that I hope the feceral highway is completely replaced. If for no other reason than the stench and santitation. 
You should explain the size here. Holes that are a couple feet big could be involed in a project to interlock the slabs of concrete, so the road stays more stable.
Somebody at the DMV has a lot of bodies to get rid of?
*evil *
Nuts, you beat me. I was going to write:
Looking for Jimmy Hoffa. 
They did something like this in central Massachusetts a few years back. It turns out that the were putting in a new roadbed material – underneath thje highway went “blankets”: of rubber made out of old tires sliced up and put together. The idea was that the road would flex and be more responsive. They took several months to install the new rubber pads, working a rectangle at a time, as you noter. I could see the “mats” before they were installed, if I went by at the right time.
I drive from PA to MD and back everyday and I know exactly what you are talking about. It is only in one lane at a time and only on the MD portion. The holes are one lane wide (of the two) and maybe only a few feet wide, about the width of the backhoe shovel. In areas where they have done work on both lanes the holes don’t line up or stagger at any noticable pattern. They have done this on both the North bound and South bound sides and it is a divided highway so the two side rarely come into contact with each other in the area being worked on. It doesn’t seem to be listed on MDOT’s current projects page and it also doesn’t seem to be related to the new bridge over the NCR trail. I’ve been wondering what the hell they are doing too.
My experience is that this is common on concrete roadways, where steel rebar (reinforcing bar) was used to reinforce the concrete.
In some cases, the roadways are penetrated by salt and other corrosives, rusting out the rebar. Scans find the weakened rebar, and sections are dug up to replace the section of concrete and rebar.
Glad to hear that someone knows exactly what I mean. The road surface is asphalt, but underneath is a layer of concrete with rebar. I have noticed that the repair work includes removing the old asphalt, concrete, and rebar, laying new rebar (which happens to be painted green–don’t know why). I have only seen them either tearing up or laying the rebar, never pouring concrete or anything else. So the explanation of some type of sensing machine finding rotted rebar sounds reasonable. I call the Maryland Dept of Public Services, and the guy I talked to didn’t know specifically anything about this, but did say repair of roadway charges are usually based on the square foot or yard. Since less than half of the roadway is having the work done, perhaps careful mapping and focal replacement save the state some money. Input from any actual roadway engineers would be greatly appreciated.
Could they be installing sensors to monitor the traffic flow? They did that out in Seattle when I lived there. Every mile or so along the freeway, there will be two small patches, about 6-by-3 feet, and about 6 feet apart. (It didn’t even look like they dug up and replaced the paving, just cut a rectangle to bury a loop of wire.) There’s a webpage that shows a map of the major highways around Seattle, color-coded with the current traffic conditions.
And a google search even turned up a press release for a project that was just started in Maryland.
I’m going to inject more confidence in addition to my original answer. The repair are a result of a rebar and concrete failure, wherein the concrete is failing as a result of corroded rebar.
There are various rebars used, and the black is the ‘old’ stuff. The green might be the epoxy coated stuffed, intended to ward of chlorides. Stainless rebar, galvinized and various coatings are employed. Supposedly, stainless is the way to go on new raod construction.
For repairs, they might choose more economical rebar (in the short term).
That certainly sounds like the most reasonable explaination. It is not for traffic monitoring as they are tearing up hundreds of these squares in total. I intuitively thought it would be cheaper to just tear up the entire lane, but I think bad rebar is the problem, from what people have written.
Simultaneous to rebar replacement, the road dept. in your state might opt to add sensors, which monitor such things as chloride ion levels and other important data to understand the environment around the rebar. Sensors would not got into every patch area. I believe wireless technology is used to monitor numerous things.
Look to see if, post repairs, a company comes out to spray the road bed. In cases where corrosives have penetrated the road surface and rebar damge has taken place, there is good Return on Investment (ROI) to hire a company that can seal the roadsurface, delaying alot of the corrosion and additional repairs. It is always about ‘delaying’.