ADUK Archive

PS - the numbers I've posted are wrong. I'll correct them later.

Done.

jont wrote:Given that, is there an optimum speed differential to use for a momentum overtake

Yes. I think it's some sort of bastardised hyperbola with a linear component. I'm not differentiating it for you.

But it's 102.7mph in this example.

Overtaking...102.7mph...

Sometimes we can overanalyse things. Its actually quite simple, as long as you overtake at the right place.

Luke wrote:Overtaking...102.7mph...

Yes, I know, hilarious isn't it; but what's wrong with it?

Luke wrote:Sometimes we can overanalyse things. Its actually quite simple, as long as you overtake at the right place.

I think you sometimes end up with a worse result if you try too hard. That may not appear to be logical, but it sometimes seems to work out like that. Maybe it's due to too much concentration on a detail that really doesn't matter that much, and consequently neglecting more important aspects.

Best wishes all,
Dave.

7db wrote:...Just factorise the difference of the two energies in the banana...

Damm, I'd love to be able to say that in a conversation...sounds like something from a Star Trek convention.

Both obviously have their place IMHO. One of the best momentum techniques is on the long open single carriageway one lane in each direction. As you close on the car in front by observing traffic towards and adjusting your speed you can time it so that you can safely overtake in a much smaller oncoming gap by having a much higher differential but as has been said you are committed earlier so your planning has to be right and to be honest without using exemptions I think it will seldom appear in day to day driving.

Luke wrote:Sometimes we can overanalyse things.

The maths is easy and available. Why discard anything that aids understanding?

Unless you are scared of numbers.

Not scared of numbers but I just think that you can't teach someone how to do a safe overtake by figure crunching.

Its just an observation on my part, no need for anyone to take the wee-wee.

I don't wish to upset our engineering/scientific brethren, but I agree with Luke. You don't learn to drive a car by figuring out all the maths behind it. An overtake is a matter of judgement and spatial awareness. If it were all down to numbers, why aren't all the best racing drivers, bowls, snooker and darts players engineers?

And YES, I hate numbers. My brain works very well with words, but numbers just do not flow smoothly. It's like trying to write with the other hand... possible but messy. Something to do with being left handed and the right side of the brain perhaps?

Gromit37 wrote:I don't wish to upset our engineering/scientific brethren, but I agree with Luke. You don't learn to drive a car by figuring out all the maths behind it. An overtake is a matter of judgement and spatial awareness. If it were all down to numbers, why aren't all the best racing drivers, bowls, snooker and darts players engineers?

And YES, I hate numbers. My brain works very well with words, but numbers just do not flow smoothly. It's like trying to write with the other hand... possible but messy. Something to do with being left handed and the right side of the brain perhaps?

I'm with you but you would be astonished how many race drivers who otherwise appear to have axle grease instead of brain tissue are happy around slip angles, dynamic COG calculations suspension geometry etc.

VinnyP! wrote:

Gromit37 wrote:I don't wish to upset our engineering/scientific brethren, but I agree with Luke. You don't learn to drive a car by figuring out all the maths behind it. An overtake is a matter of judgement and spatial awareness. If it were all down to numbers, why aren't all the best racing drivers, bowls, snooker and darts players engineers?

And YES, I hate numbers. My brain works very well with words, but numbers just do not flow smoothly. It's like trying to write with the other hand... possible but messy. Something to do with being left handed and the right side of the brain perhaps?

I'm with you but you would be astonished how many race drivers who otherwise appear to have axle grease instead of brain tissue are happy around slip angles, dynamic COG calculations suspension geometry etc.

I wouldn't be surprised, but the qualities that make them 'good' racing drivers don't generally come from an understanding of the maths. Unfortunatley, I can't drive well or do the maths!

VinnyP! wrote:...and to be honest without using exemptions I think it will seldom appear in day to day driving.

Seldom yes but that's exactly the situation that prompted my original post.

Luke wrote:Not scared of numbers but I just think that you can't teach someone how to do a safe overtake by figure crunching.

Its just an observation on my part, no need for anyone to take the wee-wee.

I think David was just trying to draw attention to the mathematical logic behind it all, but to me it's one of those things that you have to get the feel of on the road, as you gradually develop the capacity for judging things with reasonable accuracy.

Best wishes all,
Dave.

To bore you with a little more maths on this, here's a little excel programme that compares the 'classic' overtake to the 'momentum' overtake both in terms of time and distance exposed to danger for a variable range of criteria.

http://mysite.orange.co.uk/ksi/TED_new.xls (about 500kb)


Not much use to anyone really, but constructing it excercised my brain this morning while trying to think of excuses not to play 'UNO extreme' with my kids this morning (I always lose).

If similar maximum overtaking speeds are considered there is very little difference in TED between the two types of overtake.