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AASHTO is mostly silent on warrants. It gives some very
The speed for TL-2 testing is 44.x mph.
If I compare 44 to the crash testing that is valid for “high
Is there somewhere where guidance is provided related to the
Our speed limits on unposted roads is 55mph. I am
In addition to the guidance we would consider our current
Is there guidance about extending the posted speed above the
|Other Keywords||TL-2 Warrants|
|Date||November 3, 2017|
I am generally aware of three documents that have addressed warrants for bridge railings.
The first document is AASHTO’s Guide Specifications for Bridge Railing (1989).
The second document was the draft report for NCHRP Project 22-8. In that document, a figure was provided that guided conditions (speed and traffic volume) under which barrier placement was suggested for TL-2, TL-3, and TL-4. You can also obtain a copy of this figure in MwRSF report no. TRP-03-98-03.
Now I know that these three reports may not answer your question directly. In terms of speed, the 22-8 plot may actually give some help in seeing that Test Level guidance is not just correlated to impact speed in crash tests. Traffic volumes affect level of risk as well. We could have a high-speed rural road that carries very little traffic volume. In this case, one may argue that the risk is low enough that a TL-2 barrier, or even lower is appropriate, even if highway speeds are 60 mph or higher.
Further, we know that impact speeds with hardware are lower than encroachment speeds (i.e., when an errant vehicle first leaves the traveled way). Even with highway speeds, including excessive driving, we design our hardware for a slightly lower impact speed based on real-world crash data, which was used to select TL-3 impact speeds in MASH.
In your case, unposted rural roads, often with lower traffic volumes, are known to be 55 mph and would easily be considered TL-2 or less.
|Date||November 4, 2017|
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