Jersey barrier height

[CentralPAGal]

I've noticed that sometimes, even after new construction or reconstruction, the shorter Jersey barriers are used for medians, sometimes in conjunction with the taller ones. I would think that designers would want to use the taller ones (more able to deflect large trucks, less headlight glare from oncoming traffic, etc), but maybe I'm just crazy. Is there a reasoning to how the height of jersey barriers are selected for projects?

[roadman65]

I know that in many places the shorter barriers are the old ones probably back from the 50's.  I believe that US 322 still has them in Mays Landing near NJ 50, as I do remember seeing it back in 05.

US 22 used to have it in Scotch Plains, but was replaced like back in the early 80's. 

[CentralPAGal]

well, sometimes it seems like they're used in newer construction, too. back about 5 years ago or so, PennDot further screwed up reconstructed the US 15/PA 581 interchange. Along 581, most of the median barrier is constructed from the taller barriers, but under the US 15 overpass, it changes to the shorter ones before changing back to tall ones again just a couple hundred feet later. I've seen them in several other newer (last 15 years or so) construction, too, but the first example is the main one to come to mind.

[TEG24601]

I'v noticed that in Michigan as they have done reconstruction, they were increasing the height of the center barriers.  In Oregon, at least in Portland, they added green extenders to the barriers.  However, in Washington, even after reconstruction they seem to be using the same size barriers they have always used.  I actually wish it was common practice to separate all aspects of the lanes of traffic for safety reasons, and to eliminate lookie-loos.

[adventurernumber1]

I think this is what you're talking about:

https://m.flickr.com/#/photos/127322363@N08/15610186616/

This is off of I-459 in Birmingham, AL (on a mission trip this past summer). It looks like they did a resurfacing as well as a height increase on the barrier. You can see the newer white concrete at the top in the picture.

[roadfro]

Nevada uses the taller jersey barrier walls (42"?) for the median wall in all major new construction and reconstruction projects. However, there are some areas where the reconstruction might be minor so they just match up the existing wall height–they also sometimes use the original wall height for short-length barriers on the shoulder (such as a right-side wall protecting a sign bridge post).

[jeffandnicole]

I know that in many places the shorter barriers are the old ones probably back from the 50's.  I believe that US 322 still has them in Mays Landing near NJ 50, as I do remember seeing it back in 05.

That size one (for you folks that have never seen it: http://goo.gl/maps/rEy6D) is an unusually low height of about 24".  There were very few constructed to this size.  As you can see in further away in that pic, the wall height rises to normal height.

Design factors include the design speed and/or speed limit of the roadway, truck traffic, width of roadway, width of shoulder/median, etc.  A highway with a small, 1 foot left shoulder isn't going to need a stronger than normal jersey barrier because most traffic would scrape along the barrier, versus turning into it at a sharp angle. 

PennDOT's 'tall' barriers are quite thin at the top.  I'm not sure how much that would help in stopping a truck from getting thru.

[roadman65]

Pennsylvania also has center barriers that are only two inches tall with rumble strips on them.  Look at PA 309 south of I-81 and on US 22 from I-78 to Paxtonia in many places.

These were not done for safety, but for contrast.  Basically PennDOT uses them instead of painting a double yellow line.  In retrospect its a glorified undivided highway, but considered one by all map makers and ignorantly by us motorists.

[roadman]

When driving on I-81 through West Virginia in August of 2013, I noticed they were installing median barriers that seemed to be exceptionally tall (greater than 48 inches).  Gave me a bit of a claustrophobic feeling when I was in the left lane.

[Mr_Northside]

The barriers for all the PA-28 work between Millvale & the "North Shore" are short ones (including the permanent stretch just put in this last weekend)
I'm not exactly sure what they take into account when deciding which to use.