Motorway 'safe' distance chevrons

Motorway 'safe' distance chevrons

Author
Discussion

LordGrover

Original Poster:

33,531 posts

211 months

Monday 21st October 2013
quotequote all


Back of a fag pack maths gap at 70mph ~ 1.28 seconds and at 80mph ~ 1.12 seconds.

I've understood the sign to keep two chevrons apart:
car > _ > car
it's never felt quite enough which if my maths is correct is the case.

So, should it be three chevrons to be more in line with the two second rule?
car > _ > _ > car
or have I misinterpreted it all along and it's just poor English and they meant two gaps between chevrons? Even the graphic is ambiguous IMO.

Munter

31,319 posts

240 months

Monday 21st October 2013
quotequote all
So it's not just me then.

<awaits answer to question>

chris182

4,151 posts

152 months

Monday 21st October 2013
quotequote all
It is a little unclear. I took it to mean that one should be no closer than twice the distance between chevrons. Of course in the real world I just use common sense and pay them no heed whatsover.

Vaux

1,557 posts

215 months

Monday 21st October 2013
quotequote all
LordGrover said:
Back of a fag pack maths gap at 70mph ~ 1.28 seconds and at 80mph ~ 1.12 seconds.

I've understood the sign to keep two chevrons apart:
car > _ > car
it's never felt quite enough which if my maths is correct is the case.

So, should it be three chevrons to be more in line with the two second rule?
car > _ > _ > car
or have I misinterpreted it all along and it's just poor English and they meant two gaps between chevrons? Even the graphic is ambiguous IMO.
It's not "felt quite enough" for what?
It's not for stopping distance (which 2s rule isn't either at >40). It gives you nearly twice the accepted thinking distance time to react if you're just looking at the vehicle in front. (Which is why it doesn't suggest doubling the distance in the wet).
Well, that's how I interpret it.

7db

6,058 posts

229 months

Monday 21st October 2013
quotequote all
Only a fool invents the two chevron rule.

Tonsko

6,299 posts

214 months

Monday 21st October 2013
quotequote all
Often thought it would be worth painting these on all the motorways. Not that the advice would be followed all of the time, but it's a decent 'always on' reminder.

Toltec

7,159 posts

222 months

Monday 21st October 2013
quotequote all
LordGrover said:
So, should it be three chevrons to be more in line with the two second rule?
car > _ > _ > car
or have I misinterpreted it all along and it's just poor English and they meant two gaps between chevrons? Even the graphic is ambiguous IMO.
The above is two sets of chevrons apart, the same way that Monday the 11th and Monday the 18th are seven days apart. You do not count 11, 12, 13, 14, 15, 16, 17, 18 and think there are eight days in a week. wink


Vaux

1,557 posts

215 months

Tuesday 22nd October 2013
quotequote all
Tonsko said:
Often thought it would be worth painting these on all the motorways. Not that the advice would be followed all of the time, but it's a decent 'always on' reminder.
Cost?
Few drivers seem to bother with the current offering?
One set on the M6 were removed as they were causing issues.
http://goo.gl/maps/1QXZz
The satellite view shows chevrons on both carriageways, but if you go to street view, they've been taken off the northbound.

JM

3,170 posts

205 months

Tuesday 22nd October 2013
quotequote all
Vaux said:
Cost?
Few drivers seem to bother with the current offering?
One set on the M6 were removed as they were causing issues.
http://goo.gl/maps/1QXZz
The satellite view shows chevrons on both carriageways, but if you go to street view, they've been taken off the northbound.
What issues were they causing?



Vaux

1,557 posts

215 months

Tuesday 22nd October 2013
quotequote all
JM said:
What issues were they causing?
Really not sure - I think they were affecting traffic flow and/or the Police wanted them off. It was a few years ago now.

cupraray

43 posts

125 months

Sunday 27th October 2013
quotequote all
Munter said:
So it's not just me then.

<awaits answer to question>
someone will fill the gap

BileMonkey

7 posts

126 months

Thursday 7th November 2013
quotequote all
The maths is fine, it's a perception of what is required to be two chevrons apart that is flawed.

If the chevrons are 40m apart then you need to be at least 80m behind the car in front to ensure there are at least two chevrons between you at all times... That's about 2.6s @70mph.

If you were, say, 45m behind the car in front there would be fleeting moments when there were two chevrons between you, but most of the time it would be just one.

25NAD90TUL

666 posts

130 months

Monday 6th January 2014
quotequote all
I much prefer to leave a 5 second gap at 50, 7 second gap at 70 etc, imo the chevrons are not far enough apart as others have said, what are they 2 second intervals? Not enough at anything above 30mph imo.

I guess they are there for drivers who have no comprehension of a safe distance, I ignore the chevrons and maintain my own safe distance, I watch the vehicle in front pass a marker, say a bridge, and then count in seconds until I pass the same marker. I did that with an examiner onboard, and specified in commentary that I was 'maintaining a 7 second gap at 70mph', all he said was 'excellent!'

How many times have we all seen drivers less than the two chevrons apart? Me, many.

waremark

3,241 posts

212 months

Monday 6th January 2014
quotequote all
25NAD90TUL said:
I much prefer to leave a 5 second gap at 50, 7 second gap at 70 etc, imo the chevrons are not far enough apart as others have said, what are they 2 second intervals? Not enough at anything above 30mph imo.

I guess they are there for drivers who have no comprehension of a safe distance, I ignore the chevrons and maintain my own safe distance, I watch the vehicle in front pass a marker, say a bridge, and then count in seconds until I pass the same marker. I did that with an examiner onboard, and specified in commentary that I was 'maintaining a 7 second gap at 70mph', all he said was 'excellent!'

How many times have we all seen drivers less than the two chevrons apart? Me, many.
All of us many. You must drive on very empty motorways. On most that I drive on a 7 second gap, say 250 yards, would be rapidly filled by three other vehicles. Two seconds gives a reasonable amount of time to react, and therefore to avoid a hazard in front. If all drivers adopted a two second gap the already small number of motorway crashes would be greatly reduced.

simoid

19,772 posts

157 months

Monday 6th January 2014
quotequote all
25NAD90TUL said:
I much prefer to leave a 5 second gap at 50, 7 second gap at 70 etc...
Is that not a bit excessive?

109er

433 posts

129 months

Monday 6th January 2014
quotequote all
Vaux said:
Cost?
Few drivers seem to bother with the current offering?
One set on the M6 were removed as they were causing issues.
http://goo.gl/maps/1QXZz
The satellite view shows chevrons on both carriageways, but if you go to street view, they've been taken off the northbound.
https://maps.google.co.uk/?ll=53.245735,-2.401522&spn=0.000003,0.00284&t=h&z=19&layer=c&cbll=53.245735,-2.401522&panoid=xNKITp1-cUZLOc9YTeV48g&cbp=12,195.2,,0,-4.93

https://maps.google.co.uk/?ll=53.245041,-2.401465&...


LeoSayer

7,299 posts

243 months

Monday 6th January 2014
quotequote all
simoid said:
Is that not a bit excessive?
I think that's very sensible if conditions allow which they often don't.

jmorgan

36,010 posts

283 months

Monday 6th January 2014
quotequote all
I assume it is a guide and a way to try to hint at the muppets who do not leave a gap (not forgetting the limit is 70). I think it works to some degree some of the time but there is still Captain Invincible in his barge mobile that do not care.

simoid

19,772 posts

157 months

Monday 6th January 2014
quotequote all
LeoSayer said:
simoid said:
Is that not a bit excessive?
I think that's very sensible if conditions allow which they often don't.
7 seconds at 70mph, as in close to 2 1/2 football pitches?

Seems a bit much to me in good visibility and traction conditions. If there's any traffic, people will constantly be dropping into that gap.

0000

13,812 posts

190 months

Monday 6th January 2014
quotequote all
I always assumed it was supposed to be read as:

car _ > _ > car

Which I guess is pretty close to car > _ > _ > car. That feels like quite a big gap to me, but perhaps is about right for someone middle laning it in a people carrier.