Manchester City Council impose Schrödinger’s speed limit. 30mph on a motorway

[The Bald Eagle]

Is it enforceable? 

=========================================

Schrödinger’s speed limit

Published on 31 July 2024

Here’s a problem. In 2022, Manchester City Council say they reduced the speed limit on the Mancunian Way to 30mph. But it’s not clear if they have. It’s not even clear if they can.

Fair warning: this posts plumbs the depths of pedantry in the areas of legislation and signage, so if that isn’t your thing look away now. On the other hand, it does also have some jokes about hats.

At the present time, the only thing we can say with any certainty is that the A57(M) Mancunian Way either does or does not have a 30mph speed limit. Like Schrödinger’s Cat, we won’t know until we open the box.

The physicist Erwin Schrödinger first wrote about his famous thought experiment in 1935. It was meant to be a way of thinking about the problems of quantum theory, which state that particles can be in two states at once until they are observed. To illustrate this in a more understandable way, he created a thought experiment in which a cat is placed in a box with a volatile radioactive substance that may or may not kill it. You can only know whether the cat is alive or dead by opening the box. Until then the cat is in a “superposition” of being both alive and dead simultaneously.


Brand new 30mph speed limit signs on the Mancunian Way.

Manchester is presently - and unintentionally - embarking on a similar experiment in quantum speed limits. The City Council says their urban motorway now has a 30mph speed limit, something which appears to be impossible to achieve, and the legislation behind it appears to have a fatal omission.

So far their experiment is untested by the courts. Until a judge opens the box and has a look at the cat, we don’t know what the speed limit is.

Wait. This all sounds completely unhinged. Let’s go through it from the start.

The highway in the sky

Manchester’s famous Mancunian Way opened to traffic in March 1967, and was extremely novel. A bypass across the south side of the city centre, it is almost entirely elevated above ground, causing the local paper to name it the Highway in the Sky. It was one of the most famous and recognisable urban roads of the 1960s.

What it wasn’t, in 1967, was a motorway, despite the fact that it was often called one. When it first opened to traffic it was just part of the A57. For reasons that are not entirely clear it only gained its motorway wings in 1971, from which time its speed limit was 50.

It remained so for several decades, until Manchester City Council took a decision that no road in their care should have a limit higher than 30mph. On 3 November 2022 they applied a temporary order changing the limit.


A highway in the sky: the Mancunian Way crosses Brook Street.

Manchester’s temporary order expired on 13 April 2024, and we can’t find evidence that it has been extended, so at the time of publication the legal status of the 30mph limit is a complete unknown. (A permanent order has been drafted, and is due to take effect in the autumn, but we’ll come back to that.) However, even overlooking that, the whole thing is on shaky foundations.

A look is all it takes

In the UK, speed limits rely upon a simple concept that was first introduced in 1934. The idea is that a competent driver should be able to understand the speed limit by looking at their surroundings. Generally speaking, a limit is considered enforceable if that’s true.

The criteria for a 30 limit, set back in 1934, was that it applied in an area with a system of public lighting - streetlights, in other words. If you look around and the road has streetlights, the limit is 30. If you don’t see streetlights the National Speed Limit applies. The National limit is either 60 or 70 depending on whether the road is single or dual carriageway - another thing you can normally tell at a glance.

Now we also have 20, 40, 50 and 60 limits, which might override the usual ones. For that reason we use “repeater” signs, which are the little miniature speed limit signs posted at regular intervals at the roadside. They are there so that a competent driver can still look around and tell what the limit is. If there’s a little speed limit sign visible, then the limit is what the sign says.


A miniature 40 sign - a "repeater" to remind you of the limit.

An exception was introduced with the invention of the motorway. Since motorways did not have shops and houses facing them, they would never be subject to an urban 30 limit. A simplification was possible. So, a competent driver looking around and seeing they are on a motorway can just assume a 70mph limit applies, with or without streetlights, unless there are repeater signs to tell them otherwise. Hence long lengths of rural motorway with street lighting have no repeaters: it’s a motorway, so the limit is 70, and no clarification is needed.

From its creation in 1971 to the temporary order made in 2022, the Mancunian Way had a 50 limit, and had “50” repeater signs throughout, so competent drivers could look around them at any time and infer the correct limit.

The problem on the ground

Let’s assume the role of a Competent Driver and see if we can work out the Mancunian Way’s new limit.

It’s a motorway, and is signposted as one, so the default is 70.
It has streetlights, which normally imply a 30 limit.
The streetlight rule does not apply, because this is a motorway. Therefore the default is still 70.
There are occasional repeater signs for the 30 limit. So that confirms it: 30, right?
Well, it’s not as easy as that. If we remove our Competent Driver Hat for a moment and try on our Amateur Lawyer Hat instead, we will recall that 30 signs have to be correctly designed and located in order to apply, and some of those on the Mancunian Way (especially the temporary ones on A-frames) use an incorrect style of lettering. Others, at certain entrances to the road, only appear some distance beyond the “start of restrictions” signs, which implies that there’s a 70 limit between the start of the motorway and the first 30 sign


One of the temporary 30 signs on the Mancunian Way, which does not seem to comply with the regulations.

That’s only the start, though, because our Amateur Lawyer Hat also reminds us about TSRGD.

The Traffic Signs Regulations and General Directions (TSRGD) is the rulebook for UK traffic signs. A sign can only be lawfully erected, and enforced in law, if it complies with the rulebook.

In Schedule 10 of TSRGD, which covers speed limit signs, you’ll find diagram 670, a familiar red circle with numbers inside it. Its description is “maximum speed limit in mph”, and it has a number of instructions that set out the rules for its use. One of them says this.

The sign must not be placed as a repeater sign where the road is subject to a maximum speed limit of 30 mph and has a system of carriageway lighting.

Traffic Sign Regulations and General Directions 2016, Section 10, Part 4, 2.
In other words, you can’t put “30” repeaters on a road with streetlights, because the streetlights are what reminds drivers of the 30 limit.

On a motorway, of course, streetlights don’t indicate a 30 limit, but it seems that nobody involved in writing TSRGD had thought of that, presumably because nobody ever thought a motorway might actually get a 30 limit. And the rules are the rules.

The (speed) limits of possibility

Here is Manchester’s problem, then: they have attempted to restrict a motorway to 30mph, but there is seemingly no legal way to convey that fact to drivers. The system of street lighting doesn’t do it, but it is illegal to erect repeater signs because the street lights are there. They have created a road on which it is not possible for a competent driver to look around them and infer the speed limit from their surroundings.


Some entrances have no speed limit signs at all, implying a 70 limit.

That surely has consequences for whether or not the new limit is compliant with the law. If you create a limit, you must signpost it in accordance with the law, or else it is invalid. And (with the caveat that we are not lawyers and this does not constitute legal advice) it appears that there is no way to signpost this limit according to the law.

The obvious question is whether this can really be the first ever time that someone has tried to restrict a motorway to 30mph. If you’d care to try on this Road Enthusiast Hat - you’ll like this one, it has a pom pom - we will discover that there are at least three previous examples.

The most recent is on the Leeds Inner Ring Road, A64(M), where a temporary 30 was applied during bridge replacement works at the Regent Street interchange. This initially had repeater signs throughout, plus street lighting, just like the Mancunian Way - but Leeds removed their repeaters, on expert advice, in the belief that they would make the limit unenforceable.

There’s a section of M1 with a 30 limit too. A link road cutting through the roundabout and joining the northbound M1 at junction 1, Staples Corner, has a short and widely ignored 30 limit. There is no terminal sign where the motorway starts, and just two repeaters shortly afterwards, despite the road having street lights. Since the requirements for terminal signs aren’t met the limit is probably not enforceable anyway.


The start of the M1 at Staples Corner, and a questionable 30 limit.

The third and final example is unexpected. It's the Mancunian Way itself.

The 50 limit that existed until 2022 was imposed by The Motorways Traffic (Speed Limit) Regulations 1974, which created the 70 limit on motorways that we still have today. It attempted to reset the limits on all motorways, so it had a list of all the ones that had limits lower than 70, and specifically stated that the Mancunian Way - all of it - was subject to a 50 limit.

But the Mancunian Way became a motorway in 1971. Before the 1974 order, its limit was set by the Motorways Traffic (A.57 (M) Mancunian Way) (Speed Limit) Regulations 1971. They said something different.

These Regulations prohibit the driving of motor vehicles at a speed exceeding 50 m.p.h. on the Mancunian Way A.57 (M). The slip roads are restricted to a speed limit of 30 m.p.h.

Motorways Traffic (A.57 (M) Mancunian Way) (Speed Limit) Regulations 1971
For three years in the seventies, then, the Mancunian Way’s sliproads all had 30 limits - the first ones ever applied to a motorway. And that was probably the only example we’ve yet found that could be legally signposted: as long as there were signs at the start of the 30 limit, the sliproads are all short enough that no repeaters would be needed before they came to an end. It might just have been possible. It may even have been enforceable.

A legal oversight

Manchester City Council have now published the draft orders that will make the 30 limit permanent, so we do at least know that they intend for it to be permanent and that legislation will soon be in place, even if it isn't at the moment.


The Mancunian Way: enjoy it now while its experimental quantum speed limit lasts.

According to the notice the Council placed in the Manchester Evening News, the new order will do two things. First, it will establish a new 30 limit on the Mancunian Way, and second, it will revoke the Motorways Traffic (A.57 (M) Mancunian Way) (Speed Limit) Regulations 1971.

What it won't do is revoke the 50mph speed limit provision in the later Motorways Traffic (Speed Limit) Regulations 1974, which is more recent and appears to supercede the earlier 1971 order. It also won’t revoke speed limit orders for the two sections of 50-limit motorway that didn’t exist in 1971 and which were added in the 1990s. So even once the orders are published, and even if the signage problem is resolved, it's not actually clear that the existing 50 limit will be fully extinguished or that the 30 will be correctly established in law.

Where does that leave us?

Suppose a motorist is fined for exceeding the 30 limit, and takes the case to court. The courts may decide that the limit is not enforceable because the signage fails to comply with TSRGD. Or they may decide that the limit is invalid because the temporary order has expired, or that the new order is invalid because the 50 orders were never cancelled. Or, they may decide the Council have made reasonable endeavours to communicate the limit to drivers, despite the signage not complying with the letter of the law, and that revoking the 1971 order is sufficient, and thus declare it enforceable in its current form.

The Mancunian Way’s quantum 30mph limit, in other words, may be alive or dead.

We’re just waiting for a judge to open Schrödinger’s box so we can find out.

https://www.roads.org.uk/blog/schrodingers-speed-limit