Having one truss on top of one or more trusses this way is uncommon and unsafe in my opinion. I've never seen that before in my 20+ years of being quite familiar with Bailey style bridges. The top chord of the top truss is entirely unstable and subject to buckling.
Thanks Nathan and Luke for the information.Very interesting and helpful.
Among permanently installed Bailey truss bridges, Double Story pony truss bridges are rare in North America. Interestingly, this isn't quite a "Double Story Double Truss" as it appears the upper story is only single truss, while the bottom one is double truss.
It's common. It Bailey-pattern specific parlance, this is a "double story" Bailey pony.
Are those 2 bailey trusses stacked on top of each other on each side of this bridge?Never saw that before.
Monona and Crawford counties were considering replacing this bridge in late 2019/early 2020, but decided to leave it for now. It may get replaced in the next 5 - 10 years however.
It's definitely unusual and I've not seen done before myself. I don't see what benefit it would have given that the bottom trusses are already doubled. Would have expected to at least see some sway bracing attached.