Safe Speed Forums

NB: I split this from topic http://www.safespeed.org.uk/forum/viewtopic.php?t=5636 because it was an interesting new subject.
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really?

this page suggests otherwise. I'm pleased to see that you are able to change an entrenched position.

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COAST Not just somewhere to keep a beach.

A young loner on a crusade to champion the cause of the innocent, the helpless, the powerless, in a world of criminals who operate above the law.

I didn't read what I was agreeing with properly. I don't believe that instruments, analogue or otherwise, are read using peripheral vision. I wouldn't say 'never' or 'impossible', but somewhere pretty close.

It'd be interesting to theorise about the possibility of learning to read instruments routinely using peripheral vision. Or even designing instruments that are optimised for peripheral vision use.

But We don't have those skills and we don't have those instruments and virtually everyone - myself included - spends too much time looking at largely uneeded dashboard instruments.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Indeed. Imagine driving a car with no dashboard at all. Think about how much you would concentrate on the road. If all cars suddenly had their dashboards blanked out I suspect accident rates would fall.

But there'd be a lot of folk at the side of the road thumbing lifts to the nearest petrol station

i had the slightyl dubious pleasure of driving a car on the road without a speedo yesterday

(yes its probably illegal over here too)

and after an initial felling of driving blind i realised of course i was still adjusting my speed in the same way.. based on the road & hazards.

was a bit tricky through towns with progressive 90-70-50 kph limits where i just had to guess.

Our last "family" car was equipped with a speedo that failed to function correctly for the 18 months prior to us getting rid of it (it would constantly indicate 50mph regardless of the speed you were doing).

Guess what??

No accidents, no near misses, no speeding tickets, nada, zero, zilch in the way of it affecting driving.

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What makes you think I'm drunk officer, have I got a fat bird with me?

Many (and I do mean many) years ago I worked on the designb of flight deck instrumentation for airliners (Trident actually). We did this in discussion witht he company test pilots and the senior pilots from the airlines. It is clear that with analogue instruments they are used in 2 ways. The first is as instruments to give an accurate reading of speed, tremperature, fuel levels, etc, and the other as an indication of problems using peripheral vision. For example, if the oil pressure on one of the engines is slightly lower than the others then this will be noticed by your peripheral vision and then you'll want to make an accurate reading by specifically looking at the instrument. That's OK for slower jetc, but for fast combat aircraft the 'head-up' display is such an advantage.
This peripheral vision is still applicable for cars, but not for speed readings which are now deemed the prime factor in all road safety matters. It's no good noting that the needle is in the right area of the dial, it must be read very accurately - to the nearest couple of MPH.
Digital instruments must, of course, be read every time as slight anomalies won't be noticed by peripheral vision. That's why aircraft with 'glass cockpits', as modern flight deck displays are called, still have analogue-style displays with virtual analogue-style instruments except where specific readings are always needed. But then, the warning systems are so very good as well.
There is absolutely no doubt, as proved by the aerospace industry, that digital numerical displays take longer to read and mentally assimilate than analogue or analogue-style displays (i.e. round instruments with needles).

Something I’ve noticed when I’m driving my wife’s Corsa - normally I don’t like driving the car because the speedo, around the crucial 30mph area is difficult to read. The distance between 30 and 40 on the dial is a little over one centimetre and is around the 10 o‘clock position on the dial. Even someone with 20-20 vision would have to concentrate to get an accurate reading. However, at 60mph I feel much more comfortable because 60 is at the 12 o’clock position on the dial. That means that using peripheral vision I can see that the needle is pointing straight up, and I can gauge very accurately my speed without taking my eyes off the road too much.

But why, apart from making sure you aren't going to be snapped by a speed camera, do you even need to know your speed in the first place?

When you are behind a car on the motorway you don't think "oh, I'm 200 feet behind this car and travelling at 70... I better pull back about 250 feet as I'm a bit close for 70mph". Similarly, when you are slowing down going past a crowded urban street with kids around you don't just go "oh, kids... I'll slow to 17mph as that'll be safe". No, you just back off until it feels safe. Indeed, I bet when a driver is presented with a dangerous situation their actions are...

1) Reduce speed
2) Reassess if current speed feels safe
3) If speed feels safe maintain constant speed
4) Possibly, but not necessarily, check speedo

The point is that the speedo contributes nothing to safety and is not used in the first three important steps of actually dropping down to a safe speed. The speedo is not involved until you have already reached a safe speed and then maybe think "i wonder what speed i'm at now then?"

Indeed, the mere thought of spending time even glancing at a speedometer in a dangerous situation is anathema. If there are kids playing on all sides of the car as you go by the last thing you want to do is take your eyes off them to look at the speedo. Guess it could be a good excuse though... "yes officer, I crushed the kid under my car because although I felt that I was going about 10mph and was perfectly safe I had to ensure that I was under the 30mph limit so I was staring at the speedo when I heard a crunch".

I absolutely agree with maverick 808. The only reason I check my speedo is so I can keep my licence, which I know is a daft state of affairs.
The speedos on the buses I used to drive in the 80's and 90's were notoriously inaccurate and no-one took any notice of them. However I drove for 8years for the bus company absolutely accident free. It's only now in the Brunstrom world we have to live in that speedos are important.

Hi All,
Many many years ago in the days of car mechanics magazine ( around the 1970's) I think. I heard that some of the racing teams would turn the dials around on the dash so that the needles would all be at the 12 O'clock position when all O.K. i.e temp,oilpressure,revs. This was to minimise time to scan in a race. Be interesting to know the best and worst speedos for time taken to get an accurate speed reading.

Richard

The turning of the dials to give a '12 o'clock so all's well' reading was and still is used in motorsport. Of course, it doesn't apply to speedometers, just tachos, oil pressure & coolant temp really. If all the needles are vertical all is nominal. The dial with needle type of instrument does alert by positional difference and measure by the numbers around the dial.
Some digital readings are OK though, such as voltage, outside air temp, etc, but really this is for aerospace applications.

I couldn't agree about voltage. With voltage you want to know if it's 'in spec' or not. So an analogue meter with a green band is perfect.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

As I've probably said elsewhere, simple analogue instruments are amazingly powerful things. Consider that with an analogue dial one glance can tell you three things:

1. Current Reading
2. Trend (whether reading is increasing or decreasing)
3. Rate of Change (how fast it is increasing or decreasing)

As mentioned by Cooperman the "normal" position can also be aligned at the 12 o'clock position so that peripheral vision is all that is needed, and the limits of range are also immediate indicators of a possible problem.

With a digital instrument one glance gives you a static reading, once you've looked at it long enough to read the value. In fact it has to be artificially damped to hold a reading long enough for this specific reason, which makes it inherently difficult to use it to assess traend or rate of change, with at least two and more likely three consecutive readings being required to make any sort of assessment. Furthermore the reading has no inherent positional value - there is no concept of being at the limit or in the centre of a range - it's just a number.

And a more subtle effect is that the movement of a dial is very easy for the brain to interpret and to use as a guide and predictor. For example if we needed to brake down to exactly 30mph by a given point the human brain can fairly easily marry the rate of decelleration / brake application to the rate of descent of the needle, and "hit the mark" with a fair degree of precision. With a digital instrument we don't get this visual movement cue so the process of feeding back is much less intuitive.

Years ago I used to take dinghy racing sailing very seriously. You are given a pre-set countdown to the start so the idea is to synchronise a stopwatch of your own and then hit the start line going flat out bang on zero. It's very difficult to do, but we found it was a whole lot easier when we got our hands on a big laboratory timer which we strapped to the mast of the boat. Once we could relate the movement of the boat to the line with the movement of the clock hand towards zero our precision improved immensely.

Sometimes the simple ideas are the best!

Until the damned thing got water in it and stopped...

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!

My car happens to have both analogue and digital instruments.

The analogue speedo is a triumph of style over substance in that it has a very short scale (about 110deg) and maximum speed is vertical. This makes it all but useless to gauge low speeds - in fact the width of the needle is about 5mph. The revcounter is similar with max being at 12 o'clock.

The digital speedo is easily visible at low speed but is damped and lags the analogue one so that under accelleration it underreads. At constant speed, of course, it is fine.

On balance, I prefer well designed analogue instruments for the reasons outlined in JT's post above.

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Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.

I am afraid we will all end up using whatever the motor industry decides will be best for us. It is probably going to be cheaper to produce digital readouts so that is what we will all end up with and then they will produce the 'retro look' where you will have a digital representation of an analogue instrument.

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Shooting is good for you and too good for some people.

4. Deviation (how far the reading is from the desired position)
5. Condition (the scale can be marked with green / red / yellow sections)

And we can also use some of these dials - especially clocks - to do 'angular arithmetic'. If I want to know the time in six hours I can add 180 degrees and read off the time. This is especially valuable when a 'carry' is involved - like 9pm + 6 hours = 3am.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Yes, plus a speedo can display two scales (km and miles) at the same time. But for speed cameras/limit etc., we are interested in a binary condition - are we over the limit, and thus liable to get fined?

A simple beeper or a flashing light could tell us that, assuming there is a system that could detect the condition in the first place.

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I stole this .sig

Surely not.

We need much more than that to know what action to take. In an extreme example we might be 70mph over yet the indication is simply 'OVER'. Later we might be 0.1mph over and the indication is still exactly the same.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

There may be ways to increase the granularity of the warning, but if you want to know 'how much', then you have a speedo too. I think it would be interesting for people to know whether they are liable to be fined at all. It removes the option of thinking "I didn't realise I was over the limit", and it would compel people to be honest about their reasons. It doesn't have to be very intrusive, this light or beeper thingy that I’ve dreamed up.

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I stole this .sig