Overtaking with approaching junctions

[crr003]

They are not the numbers I will need nor care about when I anticipate any vehicle emerging from a junction, a vehicle speeding up as I overtake or when on blue lights the 3 vehicles in front of me indicating left to allow me to pass!

Dear Mr police Driver - with all due respect, can I suggest that they actually ARE the numbers you need, and I am a little perturbed that you suggest you do not care about them.

I wonder if what you actually mean is that you do not believe you need to consciously consider them as numbers. Well that is a different matter. However, if you are overtaking at a certain speed that dictates you need x-distance to complete it safely, then you definitely NEED to know that distance, even if you have got to know it through trial and error. You need to know it, and you need to care about it.

I think I understand what you're saying - some mathematical formulae dictate that to overtake a vehicle travelling at A mph from xM behind it (contact/overtaking position) whilst your vehicle is travelling at (A+10) mph and pull in yM ahead of it (ignoring acceleration and a non-straight path to make it simpler) requires a certain distance.
Add to this a safety factor for fast oncomers and you get a bigger distance.

Now, in a practical overtake, it's possible that you could modify the safety factor, based on training, experience and other skills, and thus reduce the overall distance.

Or increase the speed differential (but I was trying to examine a legal overtake) - Doug Holland wrote a 10 mph diff. required 12 seconds to complete the overtake.

20 mph needs 6s
30 mph needs 4s

I know I'm "shy" on overtaking and miss loads of opportunities.

An interesting observation in theoretical terms (as it would be illegal....) might be that if you overtook at 70 in an NSL (the target doing 50), you'd take half the time, half the distance and be twice as safe?

[James]

Sometimes I feel I dont explain myself very well on here.

I didnt mean to make it sound like I just pull out to overtake and hope for the best. What I am saying is that all this distance analysis is time consuming and in a fast changing enviroment (for example on blue lights where almost every second a different car,bus, cyclists or pedestrian is reacting to your presence) takes too much time. I look for my stop over gap, I look to see where I can arrive safely and mark that point, and often while travelling to it another oppurtunity or stop over gap will emerge and I can head for that one, and anotherm and another. Whilst monitering and making my way to these points, although the folliwng mat go through my mind, I am not conciously thinking:

"I can see that there is a 50m length of clear road on the other side and there is a vehicle that is approaching beyond it. I can see that I am 4 metres behind the car in front. Therefore estimating the speed of the car towards me I know I can move out and make the overtake safely as I have more than the specified distance in which to complete the maneouvre".

Instead I think;

"I can see the gap on the offside, the one towards and no other hazards. I can make the overtake safely".

Of course the distance and speed analysis is an essential part of my decision making but I am not actually sat there working out figures and distances as fractions of each other.

You do not need to use geometry or trigenometery to complete a safe overtake.

[Gareth]

Sometimes I feel I dont explain myself very well on here.

Perhaps I was baiting you just a little, but the point I was trying to put across, (somewhat more explicitly in the other thread), was that even though you might not consciously realise it, by being police trained you have been taught the skill and been provided with the experience to make such judgements, in stark contrast to the majority of motorists.

I hope you'll agree that your ability to make good decisions when planning overtakes did not just spring into being at some point in your life

[James]

No, totally, and as mentioned it IS the case that police training provides intensive tuition on overtaking whilst using exemptions. We were taken to huge long roads where you can literally oull off 6 car overtakes in groups of 2 at a time, parallelling your stop over gap before identifying the next one.

I suppose it seems unfair as Police Training is the only real effective way of learning the skill. I will never forget my instructor, "Get out there and have a look" he would exclaim on every oppurtunity just to have a peek, even if you knew the O/T probably wasn't on. As long it is safe to do so you were always expected to be having alook and adopting the O/T position on the offside to show you were thinkinh about it. Oftem an oppurtunity arose and it could be taken. By getting in the habit of being in the correct position behind the one in front, based on what the speed limit was, what the road was doing, what options they had and what sort of markings seperated the lanes, you were always in the best place for an O/T.

However, the "excercising restraint" side is often underestimated and frequently the O/T is NOT on. Even the presense of a small dirt track in the bushes on a long NSL could prove fatal.

[crr003]

Interesting! Piston Heads is exploring the same sort of thing..... (and the numbers tie up nearly.....)

http://www.pistonheads.com/gassing/topi ... &f=154&h=0

[TripleS]

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[fungus]

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Anyway, to continue the thread, and answer the OPs question, if there were evidence of a junction ahead, I would not consider the overtake on unless the junction was further than half way to the limit of my vision.

As for using X,Y, or Z number of metres to calculate half the limit point, distance covered at a given speed etc. I just don't think it's feasible, as the majority of people would have difficulty in judging what 30 metres is when stationary, let alone on the move.

[TripleS]

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Sorry about that.