Caught doing 120mph on the motorway

[Phil Dicky]

Any driver who is unaware of the difference between 120 and 70 needs to be off the road..as they certainly aren't paying enough attention to the road and the rate at which scenery is passing them...regardless of how wafty the car is !!!!

[TheAllSeeingPie]

Pete317 said:

A possible scenario: you're in a car with a quiet engine, and with music playing you can't really hear it at all.
You pull into L3 to pass what turns out to be quite a long line of traffic in L2. So in order to make progress past them you accelerate gently to add around 20mph to your speed.
But, while you're passing them, the vehicle at the head of the line moves over into L1 and the line of cars in L2 start gently accelerating up to 20mph faster.
You don't really notice they're accelerating, and you almost unconsciously press the pedal a bit harder to maintain your speed differential.
But then you see the 1-mile sign for your junction coming up, so you give just a little extra juice to pass the remaining few cars and get over to L1 in good time.
Just then you look down at your speedo to discover you're now doing around 50mph more than when you started your manoeuvre.

Perfectly plausible if you started at 40mph, but the thing is that air resistance gets exponetially higher as you accelerate which means that over 70mph it takes a significant amount more effort to add 50mph than it does at 40 or lower. I've seen this myself on runway tests of my own car where 0-60 is less than 4 secs but 60-120 is 7-8 secs and 120-160 is another 12-15 secs and that is flat out. The scenario where you're pootling past people and picking up speed really wouldn't let you put 50mph on slowly as you'd have to be passing people for around 2-3mins without noticing you'd added 50mph, seems a bit less plausible now?

[AW111]

I have finally worked out what's happening here.

German Uber barge : metric speedo!

All the waffling makes sense if you are talking 70 - 120 kph

[Pete317]

Mike22233 said:

What rubbish - I would always know when I'm exceeding the tonne mark as I consciously always make an effort never to exceed 94mph so I stay out of court if I am caught.

Yes, your conscious effort is what makes all the difference

[Pete317]

TheAllSeeingPie said:

Pete317 said:

A possible scenario: you're in a car with a quiet engine, and with music playing you can't really hear it at all.
You pull into L3 to pass what turns out to be quite a long line of traffic in L2. So in order to make progress past them you accelerate gently to add around 20mph to your speed.
But, while you're passing them, the vehicle at the head of the line moves over into L1 and the line of cars in L2 start gently accelerating up to 20mph faster.
You don't really notice they're accelerating, and you almost unconsciously press the pedal a bit harder to maintain your speed differential.
But then you see the 1-mile sign for your junction coming up, so you give just a little extra juice to pass the remaining few cars and get over to L1 in good time.
Just then you look down at your speedo to discover you're now doing around 50mph more than when you started your manoeuvre.

Perfectly plausible if you started at 40mph, but the thing is that air resistance gets exponetially higher as you accelerate which means that over 70mph it takes a significant amount more effort to add 50mph than it does at 40 or lower. I've seen this myself on runway tests of my own car where 0-60 is less than 4 secs but 60-120 is 7-8 secs and 120-160 is another 12-15 secs and that is flat out. The scenario where you're pootling past people and picking up speed really wouldn't let you put 50mph on slowly as you'd have to be passing people for around 2-3mins without noticing you'd added 50mph, seems a bit less plausible now?

We're talking about adding 20mph or so onto what we perceive the traffic speed to be at the time.
And I was even careful not to mention the limit, but my point is that you may know you're exceeding the limit by 20-30mph, but an extra 10-20mph on top of that might take you by surprise.

[Mike22233]

Pete317 said:

Yes, your conscious effort is what makes all the difference

Not really - I would find it hard to just find myself at over a tonne. Of course I am conscious as I am alert when driving.
Think half of you guys are just arguing for the sake of it

[Pete317]

gruffalo said:

Between 60 and 80 mph the noise level in an A8 more than doubles so to say that you would not realise the increase in speed is hard to understand.

Read up on sound pressure levels and perceived loudness

[Pete317]

Mike22233 said:

Pete317 said:

Yes, your conscious effort is what makes all the difference

Not really - I would find it hard to just find myself at over a tonne. Of course I am conscious as I am alert when driving.
Think half of you guys are just arguing for the sake of it

The point is, you need to make a conscious effort to accurately know what your speed is at any time in dynamic conditions. That's a conscious effort over and above the conscious effort required for more important aspects of driving.

And if you think we're arguing for the sake of it, well you didn't have to reply, did you?

[youngsyr]

Let's put it another way:

At 120 mph your stopping distance is something like 885 feet / 270 metres.

At 70 mph your stopping distance is something like 388 feet / 118 metres.

The difference between them is over 1.5 football pitch lengths.

If you can't tell whether you're going to need 270 metres to stop or 118 metres to stop, you shouldn't be on the road.

Sources:

http://www.csgnetwork.com/stopdistcalc.html
http://www.csgnetwork.com/stopdistinfo.html

[Devil2575]

youngsyr said:

If you can't tell whether you're going to need 270 metres to stop or 118 metres to stop, you shouldn't be on the road.

But that can't be right, surely most people on PH are driving gods! Well above average

[Pete317]

anonymous said:

[redacted]

I don't mind discussing what I said, but not what I didn't.

[fulham911club]

WinstonWolf said:

LoonR1 said:

WinstonWolf said:

LoonR1 said:

WinstonWolf said:

Ah, the revvy V10... It takes zero effort in the TD. Never heard the expression effortless used to describe a car?

I give up. You're seriously saying that you can apply next to no pressure to your diesel powered A8 amd it'll just zoom up to 120mph amd take you by surprise.

Be serious.

I've never said zoom, the rest is correct in the right circumstances.

Ok here it is required with the "zoom" removed, I've added "waft" as a way to describe it just meandering up to that speed, but you can change it to any word you like. You really want to stand by that comment?

LoonR1 said:

I give up. You're seriously saying that you can apply next to no pressure to your diesel powered A8 and it'll just zoom waft up to 120mph and take you by surprise.

Be serious.

I thought you were giving up?

Just stick to what I said instead of trying to make up other meanings. Not taken by surprise, surprised by how fast you are travelling. My 911 felt pretty quick at speed, my Griff feels bloody quick at 120, the A8 just doesn't.

I was just going to ignore this most ridiculous of PH threads but Wolfie is so up his own arse I felt the need.

I have a Maserati QP. Same size if not bigger than an A8. Granted doesn't have a turbo diesel but a 4.7 V8 but is barge like and comfortable etc etc. So somewhat of a comparable car.

1. It feels fast at 120.
2. It will go from 70 to 120 v quickly but not quickly enough without trying and without noticing
3. You could creep up to 120 in your "TDI" mode per WW but you would still be aware that you are going v fast.

[WinstonWolf]

fulham911club said:

WinstonWolf said:

LoonR1 said:

WinstonWolf said:

LoonR1 said:

WinstonWolf said:

Ah, the revvy V10... It takes zero effort in the TD. Never heard the expression effortless used to describe a car?

I give up. You're seriously saying that you can apply next to no pressure to your diesel powered A8 amd it'll just zoom up to 120mph amd take you by surprise.

Be serious.

I've never said zoom, the rest is correct in the right circumstances.

Ok here it is required with the "zoom" removed, I've added "waft" as a way to describe it just meandering up to that speed, but you can change it to any word you like. You really want to stand by that comment?

LoonR1 said:

I give up. You're seriously saying that you can apply next to no pressure to your diesel powered A8 and it'll just zoom waft up to 120mph and take you by surprise.

Be serious.

I thought you were giving up?

Just stick to what I said instead of trying to make up other meanings. Not taken by surprise, surprised by how fast you are travelling. My 911 felt pretty quick at speed, my Griff feels bloody quick at 120, the A8 just doesn't.

I was just going to ignore this most ridiculous of PH threads but Wolfie is so up his own arse I felt the need.

I have a Maserati QP. Same size if not bigger than an A8. Granted doesn't have a turbo diesel but a 4.7 V8 but is barge like and comfortable etc etc. So somewhat of a comparable car.

1. It feels fast at 120.
2. It will go from 70 to 120 v quickly but not quickly enough without trying and without noticing
3. You could creep up to 120 in your "TDI" mode per WW but you would still be aware that you are going v fast.

Different car feels different at speed shocker...

[Pete317]

anonymous said:

[redacted]

We're talking about adding 20mph or so onto what we perceive the traffic speed to be at the time.
And I was even careful not to mention the limit, but my point is that you may know you're exceeding the limit by 20-30mph, but an extra 10-20mph on top of that might take you by surprise.

Below is what I have surmised you mean from the above. Could you clarify if I have misunderstood.

Scenario 1 - 70mph reference point
One may know that one is doing 90-100mph. An additional 20mph, taking the speed up to 120mph may not be so noticeable.

Scenario 2 - 30mph reference point
One may know that one is doing 50-60mph. An additional 20mph, taking the speed up to 80mph may not be so noticeable.

As far as I'm aware, nobody on this thread has yet mentioned anything other than motorway driving, so I doubt that your 30mph reference point has much relevance to this discussion.

[Mike22233]

Pete317 said:

The point is, you need to make a conscious effort to accurately know what your speed is at any time in dynamic conditions. That's a conscious effort over and above the conscious effort required for more important aspects of driving.

And if you think we're arguing for the sake of it, well you didn't have to reply, did you?

No I don't - it's a normal part of being an alert driver

[Pete317]

Mike22233 said:

Pete317 said:

The point is, you need to make a conscious effort to accurately know what your speed is at any time in dynamic conditions. That's a conscious effort over and above the conscious effort required for more important aspects of driving.

And if you think we're arguing for the sake of it, well you didn't have to reply, did you?

No I don't - it's a normal part of being an alert driver

Going by what you said earlier, it seems the main reason you want to accurately know what speed you're doing is in order to avoid going to court when you do get caught.

[youngsyr]

Over a week on from when I first posted on this thread, I'm still amazed that there are supposed motoring enthusiasts who claim they cannot tell the difference between driving at 70 mph and 120 mph!

I guess this is the internet though, so people will argue black is white for sh!ts and giggles.

I notice everyone is awkwardly avoiding my point on stopping distances though - anyone going to claim they cannot tell a difference in stopping distances of 1 and a half football pitches when they're driving on the motorway?

Thought not.

[Pete317]

anonymous said:

[redacted]

No, you're the one who's full of st. I wasn't saying anything about my driving whatsoever, so your aspersions are completely misplaced.

What I was suggesting is that it might not be difficult for someone to speed up somewhat without realising it, when the traffic they're passing is also speeding up.

[JNW1]

Exige77 said:

Speeding is speeding and DD is DD

Speeding is obviously factual as there's a defined limit and you've ever exceeded it or you haven't; however, dangerous driving is surely far more subjective and hence much less black and white than you imply?

[gruffalo]

Pete317 said:

gruffalo said:

Between 60 and 80 mph the noise level in an A8 more than doubles so to say that you would not realise the increase in speed is hard to understand.

Read up on sound pressure levels and perceived loudness

The 5db increase in that report was over a 30 km increase, the speed we are talking about is an 80km speed increase so the 5db increase is likely to be much larger.
http://www.acousticsbydesign.com/acoustics-blog/pe...

Now for a quick quote for you taken from the above site.

Perception.
Sound studies tell us time and again that a 3dBA increase in sound level is barely noticeable to the human ear. In fact, you have to raise a sound level by 5dBA before most listeners report a noticeable or significant change. Further, it takes a 10dBA increase before the average listener hears “double the sound.” That’s a far cry from 3dB.

So the 5db increase is a noticeable or significant increase in perceived loudness what would the cb increase be for an 80km speed increase be, let's say 12db so very noticeable and at least perceived as twice as loud or more.