Some states are putting wire barriers in the median to prevent vehicles from crossing the median if the driver falls asleep or is involved in an accident .( A report states the barriers probably won't stop a large truck ) . My concern is the way these barriers are being installed on I-44 in Missouri . While some states put on barrier in the center of the median ( and I came on a wreck where a vehicle hitting the barrier rolled over it and continued traveling to the right shoulder of the opposite lanes ) Missouri runs barriers close to rhe left shoulder in each direction . The left shoulder is about half the width of a vehicle . Now if a vehicle becomes disabled while traveling in the left lane it cannot go to the left out of the travel lane . When the vehicle comes to a stop in the high speed lane , if the driver gets as far to the left as he can he cannot exit the driver's side because of the cable . Picture a mother with a couple of small children running out of gas or getting a flat tire in the left lane during times of heavy traffic . How many times have you seen traffic stop suddenly and someone that was following too closely hits the median to avoid a collision ? This option won't be available . Is it any safer for someone falling asleep to bounce off a wire in front of traffic traveling in the same direction ? What was the intended purpose of states buying sufficient right of way to have a median ? I think the "Show me " state is going to be shown they are making a big mistake installing these barriers too close to the shoulder .
Wire barriers in median
- Thread starter Crazynuff
- Start date
I saw them stringing that stuff a couple of months ago along I-70. Didn't pay any attention to where in the median they were putting it. You're right, it doesn't make any sense to put them that close to the left shoulder. Unfortunately once it's done it's probably permanent, no matter how many accidents and deaths it causes.
joebob1_30132
Expert Expediter
My guess would be tailgating wont be an issue the next time after they mess up once. The state assumes your not to tailgate so there is no issue.
You're right, that's a very dangerous situation, and it's pretty stupid of the MO DOT to do it. It's fine to tell us about it, but if you want to take action, tell the MO DOT that they are doing something dangerous. Here's their link:
http://www.modot.org/asp/request_information.shtml?comments
http://www.modot.org/asp/request_information.shtml?comments
>My guess would be tailgating wont be an issue the next time
>after they mess up once. The state assumes your not to
>tailgate so there is no issue.
Tailgating happens and people aren't attentive to sudden stops in the passing lane . But the real danger is to vehicles losing power due to mechanical problems and having traffic prevent them from getting to the right shoulder . As soon as a vehicle begins to slow in the left lane vehicles begin passing it on the right .
>after they mess up once. The state assumes your not to
>tailgate so there is no issue.
Tailgating happens and people aren't attentive to sudden stops in the passing lane . But the real danger is to vehicles losing power due to mechanical problems and having traffic prevent them from getting to the right shoulder . As soon as a vehicle begins to slow in the left lane vehicles begin passing it on the right .
>You're right, that's a very dangerous situation, and it's
>pretty stupid of the MO DOT to do it. It's fine to tell us
>about it, but if you want to take action, tell the MO DOT
>that they are doing something dangerous. Here's their link:
>
>http://www.modot.org/asp/request_information.shtml?comments
Thanks for the link . I'll use it and hope others do also.
>pretty stupid of the MO DOT to do it. It's fine to tell us
>about it, but if you want to take action, tell the MO DOT
>that they are doing something dangerous. Here's their link:
>
>http://www.modot.org/asp/request_information.shtml?comments
Thanks for the link . I'll use it and hope others do also.
I copied Crazynuff's post and sent it to the MO DOT, and here's their reply:
The following information was provided in response to your e-mail by Joe Jones, Technical Support Engineer with MoDOT.
The primary purpose of all roadside barriers is to prevent a vehicle from leaving the traveled way and striking a fixed object or terrain feature that is less forgiving than the barrier itself. In Missouri, cable barriers in the medians of freeways accomplish this purpose, preventing vehicles from crossing the median and impacting another vehicle head-on. The results of an accident of this type are particularly severe.
This sort of barrier consists of steel cables mounted on weak posts. It is relatively inexpensive to install and very effective at capturing errant vehicles. Missouri is using cable barrier to protect its medians less than 60’ wide. The program begins with freeways and will eventually protect the medians of expressways as well.
Guard cable, like most roadside safety hardware, is intended for use on a 1V:6H (one foot decrease in elevation for every six running feet) slope. The 1V:6H requirement is based in both computer modeling and full-scale crash testing and represents sound theory. In practice, however, slopes as flat as 1V:6H are often the exception.
In these cases, MoDOT employs one of three, brand-name systems, developed for use on slopes as steep as 1V:4H. These systems have been rigorously crash tested and approved for use by the Federal Highway Administration’s (FHWA) Office of Safety Design. Each system has subtle differences in design, but all share one element in common. The FHWA approval specifically states, “… cable design is acceptable as a TL-3 traffic barrier when placed no farther than 4 feet down a 1V:4H slope (for adjacent traffic impacts)…â€. Any state, not just Missouri, that installs cable barrier of this type, is required to place it no more than 4 feet from the inside shoulder.
Given the 4 ft. width of the inside shoulder of freeways and expressways in Missouri, and the 4 ft. downslope requirement, the steep-slope cable barrier is placed 8 ft. from the edge of traveled way. This placement may appear to be close the edge of the traveled way, but it’s important to note the inside, or left, shoulder is not intended to be a refuge. The American Association of State Highway and Transportation Officials (AASHTO) publication, A Policy on Geometric Design of Highways and Streets affirms the following.
“Shoulder space on the left side of the individual roadways of a four-lane divided arterial (i.e., within the median) is not intended to serve the same purpose as the right shoulder. The shoulder on the right, through customary use on undivided arterials, is accepted by all drivers as a suitable refuge space for stops. Where the median is flush with the roadway or has sloping curbs, vehicles may encroach or drive on it momentarily when forced to do so to avoid a crash. Only on rare occasions should drivers need to use the median for deliberate stops. On divided arterials with two lanes in each direction, a paved shoulder strip 4 ft. wide should satisfy the needs for a shoulder within the median.â€
Common vehicle widths range from approximately 5 ft.-6 in. for a subcompact car to 6 ft.-8 in. for a wide sport utility vehicle. A minivan is usually 6 ft. wide. On the rare occasion a vehicle would take refuge against the median cable barrier, the average driver and passenger would have ample room to exit the vehicle on the left side, putting neither mother nor child at risk of exiting the vehicle directly into the traffic stream.
The cable barrier in question does not cause the impacting vehicle to “…bounce off a wire in front of traffic traveling in the same directionâ€.
A roadside safety hardware feature must undergo rigorous safety tasting before it can be used on the National Highway System (NHS). Most state have adopted the same testing criteria for highways that are not on the NHS. The standard by which all roadside safety features are measured is contained within the National Cooperative Highway Research Program Report No. 350 (NCHRP 350).
NCHRP 350 evaluates safety hardware according to three general factors, structural adequacy, occupant risk, and vehicle trajectory. To successfully pass the latter, the vehicle can not intrude into adjacent traffic lanes nor can it exit the system at an angle greater than 60% of the entry angle, after the impact. All roadside hardware placed on Missouri’s freeways has passed the testing requirements of NCHRP 350, and is therefore in no danger of impacting the adjacent traffic stream.
Besides the safety inherent in NCHRP 350 certification, MoDOT now has five years experience in the use of cable barriers. The preliminary findings of a comprehensive study currently underway; suggest that of every 100 vehicles that entered the median and impacted the cable, 95 were prevented from encroaching into the oncoming lanes. Given it’s great emphasis on the value of safety, MoDOT is encouraged by this sort of success and will continue to use cable barriers.
The following information was provided in response to your e-mail by Joe Jones, Technical Support Engineer with MoDOT.
The primary purpose of all roadside barriers is to prevent a vehicle from leaving the traveled way and striking a fixed object or terrain feature that is less forgiving than the barrier itself. In Missouri, cable barriers in the medians of freeways accomplish this purpose, preventing vehicles from crossing the median and impacting another vehicle head-on. The results of an accident of this type are particularly severe.
This sort of barrier consists of steel cables mounted on weak posts. It is relatively inexpensive to install and very effective at capturing errant vehicles. Missouri is using cable barrier to protect its medians less than 60’ wide. The program begins with freeways and will eventually protect the medians of expressways as well.
Guard cable, like most roadside safety hardware, is intended for use on a 1V:6H (one foot decrease in elevation for every six running feet) slope. The 1V:6H requirement is based in both computer modeling and full-scale crash testing and represents sound theory. In practice, however, slopes as flat as 1V:6H are often the exception.
In these cases, MoDOT employs one of three, brand-name systems, developed for use on slopes as steep as 1V:4H. These systems have been rigorously crash tested and approved for use by the Federal Highway Administration’s (FHWA) Office of Safety Design. Each system has subtle differences in design, but all share one element in common. The FHWA approval specifically states, “… cable design is acceptable as a TL-3 traffic barrier when placed no farther than 4 feet down a 1V:4H slope (for adjacent traffic impacts)…â€. Any state, not just Missouri, that installs cable barrier of this type, is required to place it no more than 4 feet from the inside shoulder.
Given the 4 ft. width of the inside shoulder of freeways and expressways in Missouri, and the 4 ft. downslope requirement, the steep-slope cable barrier is placed 8 ft. from the edge of traveled way. This placement may appear to be close the edge of the traveled way, but it’s important to note the inside, or left, shoulder is not intended to be a refuge. The American Association of State Highway and Transportation Officials (AASHTO) publication, A Policy on Geometric Design of Highways and Streets affirms the following.
“Shoulder space on the left side of the individual roadways of a four-lane divided arterial (i.e., within the median) is not intended to serve the same purpose as the right shoulder. The shoulder on the right, through customary use on undivided arterials, is accepted by all drivers as a suitable refuge space for stops. Where the median is flush with the roadway or has sloping curbs, vehicles may encroach or drive on it momentarily when forced to do so to avoid a crash. Only on rare occasions should drivers need to use the median for deliberate stops. On divided arterials with two lanes in each direction, a paved shoulder strip 4 ft. wide should satisfy the needs for a shoulder within the median.â€
Common vehicle widths range from approximately 5 ft.-6 in. for a subcompact car to 6 ft.-8 in. for a wide sport utility vehicle. A minivan is usually 6 ft. wide. On the rare occasion a vehicle would take refuge against the median cable barrier, the average driver and passenger would have ample room to exit the vehicle on the left side, putting neither mother nor child at risk of exiting the vehicle directly into the traffic stream.
The cable barrier in question does not cause the impacting vehicle to “…bounce off a wire in front of traffic traveling in the same directionâ€.
A roadside safety hardware feature must undergo rigorous safety tasting before it can be used on the National Highway System (NHS). Most state have adopted the same testing criteria for highways that are not on the NHS. The standard by which all roadside safety features are measured is contained within the National Cooperative Highway Research Program Report No. 350 (NCHRP 350).
NCHRP 350 evaluates safety hardware according to three general factors, structural adequacy, occupant risk, and vehicle trajectory. To successfully pass the latter, the vehicle can not intrude into adjacent traffic lanes nor can it exit the system at an angle greater than 60% of the entry angle, after the impact. All roadside hardware placed on Missouri’s freeways has passed the testing requirements of NCHRP 350, and is therefore in no danger of impacting the adjacent traffic stream.
Besides the safety inherent in NCHRP 350 certification, MoDOT now has five years experience in the use of cable barriers. The preliminary findings of a comprehensive study currently underway; suggest that of every 100 vehicles that entered the median and impacted the cable, 95 were prevented from encroaching into the oncoming lanes. Given it’s great emphasis on the value of safety, MoDOT is encouraged by this sort of success and will continue to use cable barriers.
Tennesseahawk
Veteran Expediter
I think they give a reasonable explanation. When you look at most urban highways, you don't even get 4' before you meet a concrete wall. So, if an emergency presents itself, I'd rather hit a wire with breakaway posts. I've been thru a couple of incidents where wires would've helped enormously, as once I went into the opposing lanes. Luckily, there was no traffic. Hitting two barriers may have prevented the truck from flipping.