Overtaking Technique

[Astraist]

It has come to my awareness that the overtaking technique practiced by Roadcraft oriented advanced driving tuitions and those which are custom in Israel and elsewhere, are different. Where I was advised to maintain my original and safe margin from the car ahead and use that space to accelerate, Roadcraft suggests a closer position followed by an offside position and THAN the application of power.

I myself choose a certain Via Media, which is much like what I practice and illustrate in overtaking on dual carriageways, motorways and in general, which is done by "using up" the safe space between my car and the overtaken car to make the change of lanes as gradual as possible.

In my view, this upholds the value of smoothness as well as effectivness (since you are using up all of the available road surface) and even the goal of anticiation - since there is a longer time spawn between the initiation of the move or the signal of intetion, and it's end, giving yourself and others more time to react, correct or abort.

In overtaking on a single-carriageway, I find that overtaking this way allows to use the additional space to both accelerate and move over, while always maintaining a safe margin from the car in front and allowing to abort quite easily. Also, I find that it allows to better exploite some options to overtake, like when coming out of a bend or when another car just passed by.

The advent of the method suggested by Roadcraft is that it makes aborting even easier, simply steering back right (I mean, left...). However, the disadvantage is a longer overtaking time, longer time in the offside and a close brush with the car ahead before moving over and after aborting the overtake, should you choose to do so. I do not think that this disadvantage should be taken lightly!

I also find that this definition of "commitment" to the overtake is a tad pedantic. Just as well as you can pull back to the nearside (as suggested in Roadcraft), you could let up the throttle when you are still in the nearside, as I practice it.

Than again, the distinction between the two styles is relativelly small. To be clear, I always hog the centerline before making the move and I find that when a two seconds' gap is maintained, provides a good view at the offside and nearside up ahead. I could just as well accelerate and move timidly (but in the same manner I am used to) to the "overtaking position" suggested by roadcraft (but so that my movement into that position will not put me at risk of stepping on the tail of car in front) and than begin accelerating past...

Your thoughts and comments will be more than appreciated and I am willing to listen to any logic and change my overtaking technique if I find it necessary.

[7db]

I think the definition of "commitment" is poorly understood, and contains the key to understanding the strength of the triangle overtake.

Definition: You are committed to the overtake at the point where - should the vehicle in front apply maximum braking - you are unable to stop behind it.

The Roadcraft triangle method puts offsiding (and hence development of the superior view) prior to commitment. It can cause confusion in the target if you subsequently decline the overtake, and that is not to be taken lightly. The method of committing behind the target relies on the view not being substantially better on the offside. Even quite a small difference in speeds can use up the safe space between the vehicles and cause early commitment.

Of course it doesn't seem this way most of the time because the target doesn't apply maximum braking and there isn't an issue. But then thinking ahead through these possibilities is what marks you out as an advanced driver and the adherence to the Golden Rule.

I'd add that the notion of aiming to minimise "time exposed to danger" is misleading in two ways. Firstly "exposed to danger" is taken to be offside, whereas it should be defined as the time after you have committed to the point at which you are past. Secondly, the notion that the overtake is dangerous because of the commitment is also suspect: there are a lot of moving parts and some judgment calls to make in an overtake, but assessing them soberly and declining those which can't be safely taken means that they are unlikely to be dangerous at all.

I have (see threads from several years ago) written out the full mathematics of the two sorts of overtakes to demonstrate the superiority of the triangle pass. However intuitively, accelerating hard in a straight line does seem to be a good way to do something safely.

This is aimed at the catch and match style of overtaking. The thinking is equally applicable when generalised to the long momentum overtake. Here the point of commitment can be surprisingly early. Where you are carrying tens of mph of differential you can find yourself committed over a hundred of metres before the target, which means you might be adopting an offside position some quarter of a mile back.

[Gareth]

I have (see threads from several years ago) written out the full mathematics of the two sorts of overtakes to demonstrate the superiority of the triangle pass. However intuitively, accelerating hard in a straight line does seem to be a good way to do something safely.

Search-o-matic strikes again: 2007 thread, 2010 thread.

[ROG]

The safest method is to 'take off' from the 2 second gap but there are certain situations that need the other less safe method

What I often see is drivers starting from the safe position (when they THINK it is clear) but then rushing up to the rear of others before pulling out - what their plan is if something does forces them to abandon eludes me

[Astraist]

I see. So, the choice of a "triangle" overtake would depend on my view up ahead (including the nearside). If I have the necessary vision - I can start moving over and accelerating (hence committing to the overtake) from a safe gap from the car in front.

However, if I find that the visual field in front is compromised somehow (and I can definitely see how it might be impended) I would use the same move to advance to an overtaking position (prior to commitment) besides and behind the overtaken car, but while doing so by moving diagonally from my original position (as I would in a "normal" overtake) so I would not close up directly behind him or her.

That sounds about right, does it not?

[7db]

I think that's certainly one of the reasons -- that the vision from offside is often better (I can imagine that if you're in an artic overtaking me in my 7, then you probably have a good view from directly behind, but most target vehicles will impact the forward view).

There's a stability issue to be considered as well -- the act of steering to move offside -- as well as the effect of crossing the white lines can introduce instability in the vehicle which can be exacerbated if you are accelerating hard. I recall an overtake I made a few winters ago where I had to cross the pile of slush in the centre of the road to be fully offside (and in the cleared tracks) in order to get the acceleration on.


I think in practice I adopt a slightly blended approach. I will happily have a positive catch speed on the target prior to committing or moving offside, but position in the best place to get a view, not scare the target etc etc in order to make the decision. That's often fully offside, but not always. I think once I've got the information to go, and made the decision to go, I'm going to get on with it from wherever I am.

[GJD]

I think the definition of "commitment" is poorly understood, and contains the key to understanding the strength of the triangle overtake.

Definition: You are committed to the overtake at the point where - should the vehicle in front apply maximum braking - you are unable to stop behind it.

There are definitely two different concepts of committing. There's your definition, and then there's the point at which you make the decision to go. As you suggest, if the vehicle ahead doesn't brake, it is quite possible, for example, to get offside beyond the point of 'commitment' by the first definition, decide not to 'commit' by the second definition, and pull back in behind.

I think what you're saying is that however one goes about making the decision whether to go (committing by the second definition), one should ensure that one does not commit by the first definition while doing it. Is that right?

I haven't worked out quite how to express it yet, but I have the feeling that any inherent badness in committing by the first definition before you're ready to commit by the second might to some extent be tempered by the fact that, if the vehicle ahead did apply maximum braking, you would need far less safe road ahead to complete your inevitable pass than if they maintain their, say, 50mph. Although, of course, if they do brake hard it's quite likely to be because of some hazard that I don't want to arrive at in front of them.

[7db]

I like to imagine them slewing sideways as they brake, taking up both sides of the road. But then I have an over-active imagination.

I don't think that the definitions are in fact different ways of expressing "commitment". I think of the two things that we are talking about, one is "becoming committed" and the other is "deciding to become committed". Simply because you might successfully abort and pull back in behind the target many times, does not mean that you have full control of whether that is possible every time. You only have full control if you are able to stop in the distance which you can see to be clear. If you can't see that the distance offside past the target vehicle is clear then you can't use it to stop in. Once you can see that it is clear, then you can safely commit to it.

Furthermore, I think that "becoming committed" before "deciding to become committed" is the wrong way round to do it.

As mentioned above there is certainly a blend and an overlaid nuance of "reasonably expect to remain clear" -- this is what allows the gentle close and the closer following position - but this should be based solely on observation.

[Astraist]

If your position before overtaking is just one second short of the other car - as I understand it - than you are probably "committed" anyhow. In most circumstances, one second of a following gap (the minimum legal limit in my country, IMHO) is insufficient.

[zadocbrown]

It's easy to exaggerate the prominence of the 'overtaking position', especially if your experience of the technique is paper based rather than practical. Physically it is a transitory stage, and loitering unnecessarily in it is discouraged.

Just like the IPSGA system, the triangle overtake is as much about organising thought as actions; and like IPSGA, is employed with a (varying ) degree of flexibility.

Because the final decision is made quite late in the process, and from an advantageous position, you can be more accurate in your assessment of whether the overtake is on. This has safety and/or progress benefits. Bear in mind that 'roadcraft' has evolved for use by drivers who need to maximise overtaking opportunities; and at least on British roads, trying to overtake from a normal follow is quite limiting.

[GJD]

I don't think that the definitions are in fact different ways of expressing "commitment".

They are, I think, two somewhat different commitments. Passing someone while they maintain, say, 50mph takes a lot more distance than passing them as they brake hard. So whilst I agree that becoming committed should only happen *after* deciding to commit, I can imagine that one might have enough "reasonably expect to remain clear" information to commit to the latter while still assessing whether or not to commit to the former.

[7db]

I do understand what you are saying, and I don't think my judgement is necessarily finely tuned enough to make this the critical improvement that I would seek in changing our overtaking.

For me it's all part of that advanced philosophy of asking the "what-if" and challenging your imagination / mental library to see what bad things might happen, as well as imagining what good things might happen as the scene is revealed.

It's a bit like going round a corner with both a mental image of a long straight road for the overtake all lined up, as well as a herd of cows across the road. You hold them both in your head, planning for one and hoping for the other. You look at the overtake and try to figure out what the tightest pinch is -- misbehaviour in the target? incomers? oncomers? and then maximise your safety based on that.