Are there any forensic civil engineers in the house?
Are there any forensic civil engineers in the house?
(OP)
I'm a county engineer. One of our town highway superintendents asked us for technical assistance at a site of several fatal crashes. I have a hypothesis about what may have contributed to the latest crash, but I'd like to run it past a crash reconstruction or forensic specialist before making my recommendation. Would anyone be willing to lend an ear?
Thanks.
Thanks.





RE: Are there any forensic civil engineers in the house?
Dik
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
But I think calling the Highway Patrol or DOT is the right path.
RE: Are there any forensic civil engineers in the house?
Dik
RE: Are there any forensic civil engineers in the house?
Try one of the specialty firms such as Technology Associates (offices in New York and Florida) or Colony-Bell (Florida and other states)
Here are links...
Technology Assoc
Colony Bell
RE: Are there any forensic civil engineers in the house?
The crash site is a local road that some people like to drive on at excessive speed because they can get some air time on one of the crest vertical curves. In the most recent case, the estimated vehicle speed was 90 mph in a 30 mph zone.
I've designed a new v.c., but I strongly suspect the poor cross slope also contributed to the crashes. If I'm going to try to convince the highway superintendent to spend a sizeable hunk of his budget on truing and leveling HMA, I want to make sure I'm right.
The roadway goes from -4% excessive crown in the sag to dead flat at the crest in about 25 feet. It's -4% again in the next sag.
My hypothesis is the cross slope changes caused the vehicle to roll counterclockwise about its long axis (the right side going up) as it went over the crest, then clockwise as it came back down. The vehicle then went off the road to the right, and, perhaps because the driver overcorrected, went off the left side of the road into a tree.
So, does that sound like a plausible chain of events?
RE: Are there any forensic civil engineers in the house?
Dik
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
Is your primary objective to modify the VC such that you can't go airborne if you hit it at near triple digit speeds?
RE: Are there any forensic civil engineers in the house?
So, the super is in a spot where the town supervisor, town board, and local papers wants him to do something about it. I think highway superintendent may still be an elected position in his town, so keeping his job may also play a role.
The goal is to discourage the risky behavior, so, yes, we basically want to be Oscar the Grouch and take away their fun.
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Are there any forensic civil engineers in the house?
RE: Are there any forensic civil engineers in the house?
Personally, I DO believe that making the cross slope work better/safer for a landing after "catching air" will only encourage the behavior.
I would look into other calming measures as well.
http://www.ite.org/traffic/tcdevices.asp
Perhaps a combination of measures (alternate choke and center median, with humps before/after high point?) would be needed to create a detterant.
I deal with many municipalities which keep wanting wider streets these days and restricted street parking in subdivisions. Vehicles go considerably slower when streets are narrow with parking. Sometimes it doesn't have to be as complicated.
RE: Are there any forensic civil engineers in the house?
It's an old country road that may have never been properly engineered, and is now low-density suburban. The roadway is 1.3 miles long and 20 feet wide with narrow grass shoulders. If it were a subdivision road, the cross slope probably wouldn't be so badly out of shape.
Between the snowplow operators, the rich guy with the horse trailers, and the Porsche-driving dentists at the country club, any vertical calming features are likely to be highly unwelcome.
TerryScan, even if the vertical curve is lengthened so they don't get the hang time to begin with?
RE: Are there any forensic civil engineers in the house?
"A picture is worth..." The photo helps a good bit picturing the scenario...but it's still a bit hard to tell - is it it's own little "hump" in the road?
I do agree that a longer vertical curve may help. If one is to bother with it, I would make it A LOT longer.
*Can one cut most of that crest out?
*Otherwise, I would be trying to lengthen it by starting a fill transition at that drive to achieve length.
RE: Are there any forensic civil engineers in the house?
If anything, either eliminating the bump or adding additional material to the roadway to make the slope more gradual to,from and at the bump are the only things that would work to make everyone except for the thrill seekers happy.