This excerpt is taken from the IAM wesbsite – The Offside Rule
Off-siding, put simply is using the other side of the road to gain an advantage. The advantage is generally to increase the radius of the curve(s) that we are driving; this results in both a smoother ride and being able to carry a little more speed. A by-product of this, by reducing the amount of deceleration on approach to the hazard and acceleration after will be fuel efficiency (small I know, but it all adds up).
So, off-siding, straight-lining, call it what you will, has benefits and should be in the advanced driver’s toolbox, ready for when the opportunity arises.
It wouldn’t be advanced driving without an acronym to help us remember a systematic approach to off-siding, in this case its: SLAP.
SLAP stands for Safe, Legal, Advantageous, and Perception; it’s a simple and easy way to determine if you should straighten out a bend or not:
Safe: is our planned positioning safe? This typically refers to our view– are we certain that no one is coming towards us if considering straightening out a right-hand bend, or is there someone behind us who could be turning right if taking the straightest line over a roundabout?
Legal: is what we’re doing legal? Clearly, we must not cross any solid white lines and also follow all other instructions we receive in the way of road markings and signs.
Advantageous: do we actually achieve anything? If not, then why bother?
Perception: what do those around us likely think of what we’re doing? Are we sending them some form of car body-language that could be misleading? Or do they just think we’re being a hooligan?