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You will recall the question I asked about the need for barrier protection at median crossovers during our discussion Wed afternoon. As I mentioned, this question has been raised at the director level, and I will need to report back to them within the next 2 weeks. You both provided some excellent insight and perspectives that Erik, Bill and I were very satisfied with; however, I would like to pose this question again as a consultant request for a more formal response.
Like many states, we build median crossovers during construction to shift traffic from one set of pavements to another. Occasionally, we decide to leave these crossovers in-place rather than remove them at the end of the project. A question has been raised as to whether these median crossovers should have some sort of barrier protection or just delineated. It has been suggested that we install end protected temporary concrete barrier at these crossovers as soon as possible. Others have suggested we investigate installing cable barrier at these locations. I believe that some think having a paved surface connecting the two roadways poses a greater risk for a CMC; and therefore protection is warranted. I don't believe this question is directed providing a safe, proper design for the crossovers. I think that is a separate issue.
I've been asked to report on this issue in about 2 weeks at our May Safety Engineering Executive Group meeting that is comprised mostly of directors within our Division.
|Date||April 23, 2010|
|Response||During your recent visit in Lincoln, Dr. Sicking, Mr. Bielenberg, and myself met with Mr. Emerson, Mr. Bremer, and yourself to discuss the status of the Wisconsin DOT safety research projects. Toward the end of our meeting, you later sought comment on a potential issue involving the long-term presence of temporary and/or permanent median crossover roads between divided highways.
Median crossover roads are often used to transfer motor-vehicle traffic to the opposing vehicle lanes when construction and/or maintenance operations require the closure of selected traffic lanes found ahead. The majority of these crossover roads are typically used for short-term operations. Typically, these temporary roads are removed; however, some of these roads are occasionally allowed or intended to remain in place within the median region even though their use is discontinued. Crossover roads often remain in place due to their future use in maintenance operations or due to the high cost to remove them. Under these circumstances, questions have been raised as to whether there exists a significant risk or opportunity for motorists to utilize these crossover roads, thus potentially resulting in crossover median crashes. In addition, these questions have led to further discussions on whether the remaining crossover roads need to be protected with median barrier systems, thus preventing vehicles from traveling on the closed roads and into opposing traffic lanes.
If crossover roads must remain in place, several options should be considered for reducing or eliminating concerns for their non-approved use by motorists.
First, it may be possible to cover and/or camouflage the crossover roads with soil and vegetation to eliminate concerns for their use by motorists. Crossover roads that are covered and more closely resemble the natural median conditions should be provide no greater risk of accidental vehicle crossover than the adjacent upstream and downstream median regions. If the roads are ever needed in the future, the soil and vegetation could be removed to expose the paved road surface.
Second, if complete coverage of the crossover roads is not feasible, then partial removal of the crossover road surfaces could be considered for the first 4 to 6 ft laterally away from the outer edges of the paved median shoulders. With a 4 to 6 ft width of soil region (or other width yet to be determined), grass vegetation could be used to visually close off the roads to deter their potential use by motorists.
Third, it may be reasonable and economical to line the center region of the crossover road system with a row of closely-spaced traffic delineator posts in a pattern that runs parallel to the divided highways. A row of traffic delineators posts would be highly visible during the day as well as the night and would denote to the motorists that the roads are not for public use. If truly deemed necessary, traffic warning signs could also be strategically located to further inform motorists that the crossover roads are not for public use.
Some have suggested that median barriers should be used to close off the crossover roads in order to prevent motorists from intentionally (i.e., for turning around) or accidentally (i.e., due to driver inattention) traveling on these roads. However, the use of new containment barriers at these locations would result in new risks to motorists in errant vehicles as compared to their non-use. If barriers are not used in the median regions adjacent to the crossover roads, it would also seem inappropriate to locate barriers only across the region of the crossover roads. In addition, you noted that no accident data currently pointed to concerns at these crossover road locations. Thus, I would not recommend the use of short median barriers to cover crossover roads unless future research studies reveal that it is cost-beneficial to shield median crossover roads.
|Date||May 3, 2010|
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