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...why 142 yards?

Posted: 19 Sep 2018, 7:18pm
by mjr
Advance warning signs for Give Way and some other hazards are often "142 yards" such as the attached one.

142 yards is 426 feet and Design Table II in 1968's "Layout of Roads in Rural Areas" (which I recently got sent a copy of for another reason) gives the "Minimum Stopping Sight Distance" at 50mph as 425 feet, which is treble the dry roads and good brakes 50mph braking distance from the 1968 pre-metric Highway Code http://normandyhistorians.co.uk/hwc/1968hwc/p5.html

I guess trebling the braking distance is to allow for pretty worn brakes and pretty bad weather conditions - and I suspect the courts regard that as fair warning and don't hold the highway authority responsible for bad drivers overshooting into conflicting traffic. I don't know if this is spelled out anywhere more explicitly, though. Do you?

Re: ...why 142 yards?

Posted: 19 Sep 2018, 7:50pm
by peetee
Is it a measure of braking capacity for goods vehicles?

Re: ...why 142 yards?

Posted: 19 Sep 2018, 8:17pm
by Paulatic
Siting of signs according to appendix A of the Traffic Signs Manual is determined by
85th percentile speed of private cars (mph)

Re: ...why 142 yards?

Posted: 19 Sep 2018, 9:07pm
by NetworkMan
142 yards is the nearest yard to 130 metres. Could it be an EU directive? :)

Re: ...why 142 yards?

Posted: 19 Sep 2018, 9:12pm
by Lance Dopestrong
It's a historic convention, based upon the amount of runway needed for a Spitfire to get airborne.

Re: ...why 142 yards?

Posted: 19 Sep 2018, 9:24pm
by thirdcrank
I can't say I've ever noticed the 142. I have noted numbers in that sort of format and assumed that it was spurious accuracy caused by an over-precise conversion from metric. I've just had a look on streetview at one not far from here and there's an advance warning on the offside saying at 100 yards, then another a bit further on the nearside saying at 70 yards - ironically, part-hidden by foliage.
https://www.google.co.uk/maps/@53.78253 ... 312!8i6656

From that I take it that there's no specified distance for the placing of these signs.

Re: ...why 142 yards?

Posted: 19 Sep 2018, 10:01pm
by Sum
I'm guessing it's a combination of Paulatic's idea i.e. Appendix A in the Traffic Signs Manual and 130 metres being converted to the nearest yard (142). A quick search (google) suggests that the distance may be common in Norfolk, but not elsewhere. Maybe the Norfolkers like to be precise in their conversions?

Re: ...why 142 yards?

Posted: 19 Sep 2018, 10:11pm
by fastpedaller
It be Normal For Norfolk!

Re: ...why 142 yards?

Posted: 20 Sep 2018, 7:39am
by Mick F
Many signs are placed at the best place for them ............. the most visible and the easiest to erect.
That's not so obvious at the OP of course.

Re: ...why 142 yards?

Posted: 20 Sep 2018, 7:52am
by thirdcrank
This has prompted me to look out for these signs and it might be interesting if others did the same. FWIW, I'm pretty sure I've seen advance warning signs of things like low bridges which are placed at the last suitable junction for avoiding the hazard with distances in yards to three figures. I've always assumed that an initial round figure in metres has been converted to yards producing spurious accuracy.

Re: ...why 142 yards?

Posted: 20 Sep 2018, 12:29pm
by mjr
Sum wrote:I'm guessing it's a combination of Paulatic's idea i.e. Appendix A in the Traffic Signs Manual and 130 metres being converted to the nearest yard (142). A quick search (google) suggests that the distance may be common in Norfolk, but not elsewhere. Maybe the Norfolkers like to be precise in their conversions?

How do you get 130m from the table in the traffic signs manual? It's 2/7ths of the way up the 41-50mph range, so assuming that's not linear, why would they think the 85th percentile speed on 60mph minor roads might be something like 44mph?

The signs seem to occur on wider NSL minor roads which don't have clear sight of the T junction, usually onto an A/B road. If it's a A/B road, then advance direction (map) signs come first. I had a bit of a browse of streetscape pictures of places I know and Northamptonshire and Buckinghamshire seem to favour 100 yards, which seems almost as arbitrary. In Somerset or southern Lincolnshire, on the few suitable roads I found, you seem lucky to get a Give Way sign on the junction itself now!

Re: ...why 142 yards?

Posted: 20 Sep 2018, 2:10pm
by thirdcrank
The position of these advance warning signs is specified in S2 Junctions (P 10) of the Traffic Signs Manual, Chapter 4.
https://assets.publishing.service.gov.u ... ter-04.pdf

Too much to quote, but my reading of it is that the signs have to be positioned appropriately for any junction where there are not sufficient sight lines. There are various distances/speeds quoted in broad terms. I cannot see anything which gives a rigid formula. All the distances are quoted in metric but at a cursory check, I've not seen anything which would produce 142 yards. And certainly nothing which would produce 142 yards repeatedly.

Re: ...why 142 yards?

Posted: 20 Sep 2018, 3:57pm
by colin54
Lance Dopestrong wrote:It's a historic convention, based upon the amount of runway needed for a Spitfire to get airborne.


Droll man ,lol droll in fact.

Re: ...why 142 yards?

Posted: 20 Sep 2018, 9:45pm
by Sum
mjr wrote:
Sum wrote:I'm guessing it's a combination of Paulatic's idea i.e. Appendix A in the Traffic Signs Manual and 130 metres being converted to the nearest yard (142). A quick search (google) suggests that the distance may be common in Norfolk, but not elsewhere. Maybe the Norfolkers like to be precise in their conversions?

How do you get 130m from the table in the traffic signs manual? It's 2/7ths of the way up the 41-50mph range, so assuming that's not linear, why would they think the 85th percentile speed on 60mph minor roads might be something like 44mph?

It's not that unreasonable a guess, I can think of quite a few NSL roads where the traffic doesn't attain the limit, and you mentioned 50mph in the OP. EDIT: Although, now that I've found the signs in the OP on Google Maps, I can see why you may be sceptical.

According to the Traffic Signs Manual, the 85th percentile speed is measured:
85th percentile speed measurement is dealt with in TA 22 “Vehicle speed measurement on all-purpose roads” in Volume 5 of the Design Manual for Roads and Bridges (see para 1.3). The dry weather spot speed should be used.

I haven't had time to read it though. Maybe a FOI request would be easier.

Re: ...why 142 yards?

Posted: 1 Oct 2018, 8:32pm
by ChrisF
I've been riding / driving in France for the last 5-6 weeks, and every 'give way' / 'stop' sign on rural roads (80 kph limit now, it was 90 kph until July this year) is placed at 150 metres. It's very consistent. In towns (where there's a 50kph limit) they're placed closer and varies according to buildings, line-of-sight etc.
So the UK 142 yards doesn't convert to a EU directive, or if it does the French don't abide by it.