Should the NSL sign be abandoned?

[Kinitawowi]

On metrication, cost isn’t really the problem: this isn’t as expensive as you’d think. For reference, Ireland’s speed-limit metrication cost €10 million in 2005 (£7M at the time, equivalent to £10 M now) - €5 M to change/erect 35,000 speed-limit signs, and as much again on a public awareness campaign; even if you assume that the UK (with 13x the population, but more bigger cities) would have at least 30~40x the number of signs to replace that Ireland had in 2005, you still only have a cost of £40 million to swap over, including the cost of a bigger public information campaign.

The bigger logistical problem is that the UK still signposts distances in miles and yards, and unless that was also planned to change, there’s no real logic to changing the speed signs, except as a courtesy to European visitors. Ireland’s speed-limit change came at the end of thirty years of using only km distances on new signage. Unlike the distances, the speeds had to be changed in one day.

The DFT estimated the cost as £560M-£640M in 2005 (mostly labour costs; signs themselves were £269m, of which speed limits about £150m), and by 2009 they were allowing £760M for it.

I'm not sure how you multiply £7M by 30~40 and end up with £40M.

[KrisW]

That sounds like a cost for full metrification of all signage, which is a much bigger job (it also sounds like DfT giving Government what it wanted: “reasons not to do it”). But the scale of cost sounds like the various agencies do not have adequate records of where road-signs are in place, and a full survey would be needed. There are also some individually expensive jobs, like electronic signs, but those are small in number, so their high unit cost doesn’t contribute a lot to the total.

I'm not sure how you multiply £7M by 30~40 and end up with £40M.

I didn’t. I said the 2005 Irish cost would be £10 M in today’s money (based on conversion to GPB in 2005, then UK inflation since), of which half was on the actual replacement, so that would give £5 M spent on the signs to do an “Ireland-sized” job. Multiply that by “30 to 40” to account for sizes (UK is around 13x Ireland’s population, but has far more large cities), which gives an upper-bound of £20 M. The Irish campaign required as much spent on public education as actually replacing the signs, and I don’t imagine the UK would be different, so allow the same again for education. £20 M + 20 M = £40 M.

But the cost of replacing the NSL signs with explicit limits (still MPH) would be much, much smaller than either estimate.

[AndyB]

I think you’ve missed a zero - 5 x 40 = 200

[Vierwielen]

That sounds like a cost for full metrification of all signage, which is a much bigger job (it also sounds like DfT giving Government what it wanted: “reasons not to do it”). But the scale of cost sounds like the various agencies do not have adequate records of where road-signs are in place, and a full survey would be needed. There are also some individually expensive jobs, like electronic signs, but those are small in number, so their high unit cost doesn’t contribute a lot to the total.

I'm not sure how you multiply £7M by 30~40 and end up with £40M.

I didn’t. I said the 2005 Irish cost would be £10 M in today’s money (based on conversion to GPB in 2005, then UK inflation since), of which half was on the actual replacement, so that would give £5 M spent on the signs to do an “Ireland-sized” job. Multiply that by “30 to 40” to account for sizes (UK is around 13x Ireland’s population, but has far more large cities), which gives an upper-bound of £20 M. The Irish campaign required as much spent on public education as actually replacing the signs, and I don’t imagine the UK would be different, so allow the same again for education. £20 M + 20 M = £40 M.

But the cost of replacing the NSL signs with explicit limits (still MPH) would be much, much smaller than either estimate.

If I recall correctly, the United Kingdom Metric Association at the time came up with a figure of the order of £50 M (using the Irish model) while the British Measures and Weights Association came up with a figure of the order of £2 Billion (using a super-big-bang model). One model would be to introduce a "metication levy" of 0.2% on all new vehicles which would be spent soley on metrication. Assuming 2 million new vehicles at £20,000 each, the annual sum raised would be £40 per vehicle or £80 million per annum. There would be a mix of replacing life-expired signs (no cost) then motorway and trunk road signs (to give maximum exposure for minimum cost) followed by speed limit signs. Non-trunk road signs would follow until it was decided to remove teh levy and to only replace the remaining signs on a life-expired basis.

The real cost would not be measured in pounds but in votes - a 0.2% levy on new vehicles would hardly be noticed.

[KeithW]

So what are the costs here being discussed ?

Is it just replacing NSL signs with 60/70 or is it metrication as well ?

If its the latter I would like to see some basis for the number of signs that would need to be replaced, my concern is that given how many 20 signs are popping up all over the place who knows what the real number is ? There will almost certainly no central or even dispersed database, I would expect it to a mixture of local limits which at best on paper or nothing, limits on trunk roads should be better but I wouldnt bet on it.

Having a mixture of signs out there is a recipe for chaos in my opinion.

[KrisW]

I think the only realistic discussion is the replacement of NSL signs with 60 or 70 roundels as appropriate. The diversion into metrication is partially my fault, but it was to give an idea of the actual cost of replacing approximately 35,000 speed-limit signs, from which you could form an estimate for the UK.

Unlike metrication, however, an NSL-to-explicit-limit changeover could be rolled out as part of a regular maintenance programme, which would dramatically reduce costs. The benefit is that you’re not relying on drivers to have sat their test in the UK: the rule reduces down to “there are speed-limit signs, they all have a number on them, the number is in miles per hour”. Fortunately, visitors accidentally misreading the sign as a km/h figure is not dangerous as the opposite case.

I think you’ve missed a zero - 5 x 40 = 200

You’re completely right! My apologies for accidentally misleading you all. With that correction, the total would be around £250 M (the information campaign would cost so less per capita than Ireland’s did).

My estimate of 40x for number of signs was very much a high-ball, though: the UK’s population is only 13x the size of Ireland’s, and while Ireland has more miles of road per capita, the UK has more cities, and cities tend to be stuffed with speed-limit signs. Plus, local authorities in the UK really like erecting signage...

But on that basis, the UKMA’s estimate of £50 M is obviously far too low, but it’s probably closer to a real cost than the figure put forward by the British Weights and Measures Association.

A last observation on any theoretical shift to metric: it doesn’t really matter if you do speed-limits first, or distances; but you do have to do the limits overnight, while the limits can be phased in over a period of years. Ireland had around a ten-year period where distances would change between miles and km depending on how old the signs were, but everyone figured it out: mainly because the design changed (Ireland adopted the UK’s signage system, but using metric distances), but also because the metric ones had “km” on them (and still do).

[orudge]

And it'd mean consistency with things like Scottish motorways and Special Roads that have explicit 70 signs on them (are there any of the latter left now?).

The A55 at Colwyn Bay certainly still had them in 2021. The A90/A956 AWPR (built as Special Roads) opened a few years ago with standard NSL signs; they were then replaced with 70 signs a couple of months later!

[Chris Bertram]

... the UK has more cities, and cities tend to be stuffed with speed-limit signs ...

This shouldn't be the case. Restricted roads with streetlighting don't need their 30mph limits to be signed exept at the entries/exits from the restricted road area. However, with more councils falling under the spell of the dubious "slower is safer" and "20's plenty" mantras, there has been an increase in signage clutter.

[Chris Bertram]

And it'd mean consistency with things like Scottish motorways and Special Roads that have explicit 70 signs on them (are there any of the latter left now?).

The A55 at Colwyn Bay certainly still had them in 2021.

Still did when we were there in the new year.

[SteveM]

That’s not really a strong argument. HGV and Bus drivers have to take special training before they’re allowed drive their vehicles. Part of that training ensures that they know that their vehicles are subject to different maximum limits. Motor homes below 3.5 tonnes have exactly the same limits as cars; those over 3.5 tonnes now need you to pass an additional driving test to drive them, part of which covers the different speed limits for such vehicles.

Right now, British truck or bus drivers know that the “70” sign on the motorway entrance doesn’t apply to them. What would be different about a "60" sign on an A-road?

Not sure if that argument stands up in law. If a sign is saying '60' or '70' it doesn't matter that 'trained drivers' know they must do less. The sign is the standard. Hence the symbol (which has defined legal meaning, representing different speed limits for different classes of vehicle) is what is legally enforceable.

This is just an extension of the wider situation over signs and markings, where (e.g.) offenders are able to get off speeding tickets because a tiny bit of line was missing, or a speed limit sign is in the wrong place. The law is an ass, but a very closely defined and delimited ass.

[KrisW]

That’s not really a strong argument. HGV and Bus drivers have to take special training before they’re allowed drive their vehicles. Part of that training ensures that they know that their vehicles are subject to different maximum limits. Motor homes below 3.5 tonnes have exactly the same limits as cars; those over 3.5 tonnes now need you to pass an additional driving test to drive them, part of which covers the different speed limits for such vehicles.

Right now, British truck or bus drivers know that the “70” sign on the motorway entrance doesn’t apply to them. What would be different about a "60" sign on an A-road?

Not sure if that argument stands up in law. If a sign is saying '60' or '70' it doesn't matter that 'trained drivers' know they must do less. The sign is the standard. Hence the symbol (which has defined legal meaning, representing different speed limits for different classes of vehicle) is what is legally enforceable.

This is just an extension of the wider situation over signs and markings, where (e.g.) offenders are able to get off speeding tickets because a tiny bit of line was missing, or a speed limit sign is in the wrong place. The law is an ass, but a very closely defined and delimited ass.

I cannot comment on UK law, but in Irish traffic law, speed limits are defined in legislation, and the signs exist to inform drivers that the limit is in place: they do not, of themselves, create a limit. Simply mounting a sign on a pole is not sufficient to create a speed limit, just as the removal (through damage or neglect) of a sign does not cause the limit to be removed.

As of right now, if a sign says 60 or 70, that applies only to passenger-cars without trailers. Drivers of other vehicles may be subject to a lower limit. The legality of this is pretty clear, as it's Rule 124 of the Highway Code: https://www.gov.uk/guidance/the-highway ... 58#rule124

If you are caught exceeding that lower speed limit in a bus, or in a car while towing a trailer, you will be issued with a FPN.

[KrisW]

... the UK has more cities, and cities tend to be stuffed with speed-limit signs ...

This shouldn't be the case. Restricted roads with streetlighting don't need their 30mph limits to be signed exept at the entries/exits from the restricted road area. However, with more councils falling under the spell of the dubious "slower is safer" and "20's plenty" mantras, there has been an increase in signage clutter.

Yes, it was the 20 signs that I was thinking of, plus the use of 50 and 40 on urban arterial routes.

[Kinitawowi]

The link I posted up top specifically mentioned increased use of 20mph zones as part of its sign number estimates (and, aside from speed as the article talked about a whole metrication plan, more "Humps for 206 yards" signs).

[oddwaggonway]

...Cars for the past 10+ years have been showing the speed limit on their displays...

I had an interesting temporary driving job 4 or 5 years ago, driving the then new Ford Connect. (In the UK)
No one told my mate and I.
Kept seeing this random number flash up on the dash. Sometimes it would 60, other times lower. But occasionally it would be 100 or more
Took a while to find out that the computer was reading the speed limits off road signs and occasionally somehow saw treble figures. Had assumed it was done by GPS.
Plod probably wouldn't have taken it as an excuse if we got stopped

[Chris Bertram]

My car reads road signs. This sometimes means that it picks up a speed limit from, e.g. an adjacent road, such as at M54 just after J2 where A4510 runs parallel. M54 has the standard motorway límit of 70, which is unsigned. A4510 has a 40 limit, and as it's very close, my car picks up the repeater signs and shows me a 40 limit too.

It has also been known to pick up the limits on roundels at the back of trucks and vans, some of which may be in km/h and in three figures, and badly-angled signs on side roads that face the main road. If automatic speed limiters in vehicles are ever to be implemented, there are a good many of these kind of niggles that will have to be sorted out or there could be carnage.