most like illegal in all states here in the US. and most likely most of the modern world. maybe Australia might allow it.
brakes are the big item ticket, and the mower/conditioner swerving out into on coming traffic or into a sidewalk.
most likely over legal "length", without a permit. mower/conditioner and a 2 trailer setup if you will = excessive turning radius. that mower/conditioner is going to cut across a good amount of traffic lines. more so when turning. example at a 4 way stop, and wanting to turn left, he more likely clip person waiting there for him to make a left turn. when doing right hand turn. more likely take out good portion of intersection, plus run mower/conditioner up on sidewalk some. if you have ever seen semi drivers, take a large sweeping turn into on coming traffic, before turning into some place. same like doing for this setup, but much more uglier.
Over length? Unless both towed units are over 28' I don't think that over length would apply.
Not legal to tow as doubles I could see (It MAY be legal in NH as the mower is an ag implement per the quote below, but I cant find a sourced reference).
http://trailers.com/state-laws/new-hampshire.html said:
No vehicle may tow on any road more than 1 vehicle, trailer, or semitrailer, except one used exclusively for agricultural purposes or authorized by the DMV to do so.
As for tracking, I suspect that they would track better than a single longer trailer given the pivot point in the middle.
Brakes I could see as it weighs 4520#, but NH probbaly has an exception to not require brakes on ag equipment, so it may indeed be legal.
It looks like the mower conditioner is a
Kuhn FC 353 GC which is 11.5' wide and weighs 4520#. Of note, it connects using the lower links of the 3 point hitch, so it CANNOT be towed behind the truck (unless someone were to rig up some kind of hitch for it).
I would argue that while it might not be legal, it is probbaly safer than pulling it behind the truck or tractor because:
1. It can do 30MPH instead of 15-20MPH which will reduce the speed differential and make it less likely that some moron will cause an accident trying to pass.
2. The truck and trailer (assuming that all brakes work) can probbaly outstop the tractor and mower on blacktop.
3. It looks like the tractor is well secured (looks like ratchet binders and at least 3/8 chain on all 4 corners).
It might even meet the NH combination braking requirements (you must be able to stop from 20 MPH in 30 feet on a flat paved surface).
Aaron Z