Let's look at the physics surrounding load stability.

Referring to an example of a large crane boom mounted on a float (pictured above), we see from the following rear elevation in the image below, the height of the load (boom) center of gravity (COG) in relation to the 2.5 m legal float width configuration (on the left side).

Crane booms can weigh up to 20 t with the COG  3.1 meters above the road. In this case, the triangle of stability is drawn off the centre line of the outside tyre assuming there is some deflection and negating suspension travel.

In theory this stationary float will tip at around 19 deg of tilt. Looking at the right hand image, if the float is widened to 3.1 m then the stationary angle required to tip the float is much larger at 24 deg.

Note: the Float/trailer Mass and its COG are ignored here as it is constant between the two configurations and not the focus.

Lateral Force Generated From Cornering Speed

Tipping angles mentioned above are all well and good, but what makes the float tip in the first place?

Assuming we are driving on a road with minimal camber, the main factor influencing the tendency to tip, is lateral force.
Here is the lateral force acting on the 20 t boom as the float travels around a corner.
This Centrifugal Force is defined by the equation:
F_centrifugal = mass x velocity² / radius
If we take a 300m radius turn and a speed of 80kph (22.2ms^-1) we get
F_centrifugal = 20,000 x 22.2² / 300 = 33kN
Lowering the speed to 60kph (16.67ms^-1)
F_centrifugal = 20,000 x 16.67² / 300 = 19kN

Effect of Velocity

As velocity is squared in the equation, reducing the speed by only 25% has resulted in a 42% reduction in centrifugal force acting on our boom.

Tipping Moments and Stabilising Moments

Looking back at our narrow float, the 80 kph 33 kN tipping force must act perpendicular to the 71 degree stability line of our narrow trailer.  So the real tipping force and tipping moment are actually:

F_tipping = Cos(90-71) x 33 =  31 kN.
Tipping Moment = F_tipping x radius = 31kN x (3.1m / sin(71)) =  102 kNm

BUT if we have used the wider float and 66 degree stability triangle, then we have a slightly lower tipping force but it is offset by a longer radius (brown line).

F_tipping = Cos(90-66) x 33 =  30 kN.
Tipping Moment = 30 * (3.1/sin(66)) =  102 kNm

Where we see benefit is the stabilising moment
This is represented above by the green arrow acting downward from the Load COG at a radius (also shown in green) to the assumed pivot point - center of the outside tyre. The  calculation is  the boom mass x gravity x half the ground contact width.

For the Narrow Float.
_{Stabilising Moment} =   20,000 x 9.81 x (2.19/2) = 215 kNm 

For the Wider Float 
_{Stabilising Moment} =   20,000 x 9.81 x (2.79/2) = 273kNm 

A 27% increase in Stabilising Moment for the Wider Float

So what's the takeaway from all this?

It's simple really, when in doubt - slow down! Especially with awkward, high COG loads.

Widening your float from 2.5m to 3.1m makes a big difference to stability (27%), reducing your speed from 80kph to 60kph on corners does a lot more (42% reduction in the lateral force acting on the load).

There are a lot of unforeseen factors that can cause problems. Uneven road surfaces, off cambered corners and obstacles forcing sudden evasive action often happen without warning. It is crucial for all road users including heavy vehicles, to pay attention to advisory speed signs and slow down even more if the road is uneven or  if the visibility is poor.  Lower speeds are an insurance policy when things go wrong - they may just save your load, your career or even your life.