Wisconsin had some questions about traffic signal pole exemption and TCB transition cap which are addressed in the response below.
I have some information on the items we discussed on the phone today. First, you requested If we had any information on the reasoning behind traffic signal poles in the median having an exemption from requiring they be protected. While it would be best to protect all median hazards, there are some arguments that have been made to exempt traffic signals. 1.First, traffic signals serve to control accidents at intersections. Thus, if the signals were allowed to breakaway or disengage when impacted, the loss of the signal could cause secondary collisions that were more severe that impact of a single vehicle with the traffic signal support.
2.Second, if the intersection is functioning properly, the speeds of vehicles approaching the signal support would often be decreasing or reduced as compared to remainder of the roadway.
3.Third, traffic signal supports located in the median can only truly be shielded from one direction of traffic, shielding from both directions would require that shielding extend from the support into the intersection. This is not feasible. I also looked into your questions regarding the overhanging piece of steel on the TCB median barrier approach transition cap. On the tested system, we designed the cap to match the slope of the sides of the PCB section. Because the tops of the PCB section and the median barrier were not aligned, the cap had an overhanging piece of steel on the oncoming traffic side. This piece is not required for cap designs that match up to barriers of different widths or heights. Changes in the height of the median barrier will require a different cap design. We would require the following.1.All cap designs use the same vertical slope for the cap as the tested design.
2.The sides of the cap should match the side slope of the F-shape PCB segment.
3.If the cap is longer than the tested cap design, intermediate anchorage should be provided on the side of the cap at the midspan length to provide additional anchorage. I have attached details for a representative cap for a transition from 32" PCB to the Wisconsin 56" single slope.
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