Yet another argument in favour of switching to metric road speed limits has emerged since Wales switched the default speed limit in built-up areas from 30 mph to 20 mph two years ago.
According to the car insurance firm esure, “The average driver could be looking at a £50 saving per year on their car insurance premium if 20mph zones, such as those introduced in Wales last year, were rolled out in towns and cities across the UK”.
This equates to a metric speed limit of approximately 30 km/h.
Drivers in Wales are already benefiting from such reductions in their insurance premiums. Lower premiums in Wales have been possible because of a 35% reduction in the number of people killed on affected residential roads, while the number of serious injuries has dropped by 14.2% and slight injuries by 31% year on year.
As was pointed out in a previous Metric Views article, the safety benefits of reducing urban speed limits could have provided, and still could provide, the catalyst needed for the Government to switch all road speed limits to metric units. It would make no sense to spend millions of pounds changing thousands of road signs as a result of lowering speed limits, only for them all to have to be changed again when the Government finally sets a date for switching road signs to metric units.
Not only this, but the largest component of the cost of switching from 30 mph to 20 mph in Wales was the cost of replacing road markings. Roundels painted on roads to show a limit of “30” had to be removed and repainted to show a limit of “20”. The average cost per road marking, including overheads, was estimated to be £3920. Road markings were changed at 4700 locations in Wales, resulting in a total cost of £18.4 million, which represents 68% of the total cost of the switch to 20 mph speed limits.
Switching to metric speed limits at the same time as lowering urban speed limits would have completely removed any need to replace 30 mph road markings. Before the changeover, the “30” road marking would have read as “30 mph”, and afterwards it would read as “30 km/h”.
The chance for savings to be made in Wales has gone now, and the Scottish Government also has a national commitment to see all appropriate roads in built-up areas having a safer speed limit of 20 mph by the end of 2025.
However, if England follows suit with its neighbours and lowers urban speed limits, savings can still be made, so long as the reduction of speed limits is synchronised with a UK-wide switch to metric speed limits.
References
Reducing speed limits to 20mph could reduce policy costs for drivers by £50 per year, says insurance firm esure.
https://www.esuregroup.com/media/4oikrkcw/reducing-speed-limits-to-20mph-could-reduce-policy-costs-for-drivers-by-50-per-year-says-insurance-firm-esure.pdf
Wales 20mph speed limit saves lives – and £45.5m – should England follow suit?
https://www.boltburdonkemp.co.uk/our-insights/posts/wales-20mph-speed-limit-saves-lives-and-45-5m-should-england-follow-suit/
Transport for Wales: Vehicle speed monitoring data: July 2023 to January 2025
https://tfw.wales/vehicle-speed-monitoring-data-july-2023-to-january-2025
Explanatory Memorandum to the Restricted Roads (20 mph Speed Limit) (Wales) Order 2022
https://senedd.wales/media/fo3ibze5/sub-ld15187-em-e.pdf
20mph in Aberdeenshire towns and villages
https://www.aberdeenshire.gov.uk/roads-and-travel/20mph
20’s Plenty for Us
https://www.20splenty.org/
Metric Views 
I’ve frequently thought it would be a slick move to simply change mph to km/h in speed limits where there is a numerical sign – considering that a lot of places don’t have a number sign or have the diagonal black line on white instead. 30 mph? 30 km/h. 50 mph? 50 km/h. And so on.
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Has the coordination of the reduction in speed limits with a move to metric been suggested to the relevant local authorities?
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As much as I like the idea of using existing mph signage and markings to show the same numbers but to become metric as part of a switch to metric units for speed and distance, I think this would be far too clever for the good old British authorities. It would also have to be accompanied by a sweetener for the general public such as raising the national speed limit to 120 or 130 km/h on motorways. It’s really trying to do two things at the same time and I don’t think the authorities work like that. But it’s not inconceivable and, as an earlier poster wrote, it should be suggested to the Department for Transport.
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Speed limits require a complete reform, and this could well be combined with metrication. Let me sum up speed limit indication in the UK.
1. No indication. This applies to motorways where the limit is 70 mph. One is expected to just know this. If a lower limit applies on a motorway, see no.2.
2. A number in a red circle indicates the speed limit on that stretch of road.
3. A black diagonal bar on a white circle indicates 70 mph on a dual carriageway road and 60 mph on a single carriageway road.
4. Street lighting. On lit roads the limit is 30 mph unless a sign indicates otherwise. Repeater “30” signs are prohibited on these roads.
5. No. 4 does not apply to motorways. If a stretch of lit motorway needs to have a 30 mph limit, “30” signs must be applied.
Speed limit indication in USA, Canada and many European countries.
1. A number indicates the speed limit from this point forwards until a different speed limit is indicated.
2. Erm – that’s about it.
This complicated leglislation in the UK as arisen for historical reasons. The black diagonal on the white circle used to mean “no speed limit”. When speed limits were applied to all roads, it would have been reasonable to retain this sign with its new meaning for an interim period, pending phasing in of replacement numberical signs indicating the actual speed limits. Instead, more than 50 years on, these signs are still being newly installed – usually to indicate that on leaving a major road with a speed limit of 50 or less you have joined a narrow winding road where you can legally do 60.
The rule about street lighting indicating 30 mph limit dates back to before WW2, when the first speed limits were introduced in built-up areas. It made sense in those days but nowadays it prevents repeater ssoed limit signs in the interests of safety.
Last year I visited Norway. I noticed that a common speed limit in towns is 40 km/h. This could be a good compromise – not feeling so slow as 20 mph (30 km/h), but steadier and safer than 30 mph (50 km/h). Present reguations require speed limits to be in multiples of 10. So metrication would permit finer gradation of speed limits. Likewise, 70 km/h would be a useful speed limit for many unclassified rural roads, but this is not a near-round conversion of any mph limit.
We need, therefore, a full review of speed limits. Up to now any amendments have been based on specific aspects without consideration of the whole picture. We need a vision for the future, and a plan of how to build this vision in stages. The vision would of course be fully metricated.
Simply replacing mph with km/h would not work well. To change the speed limit of a decent stretch of road currently with a 50 mph limit to 50 km/h would be very unpopular. UKMA would not enhance its public image by suporting such a proposal.
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The only situation that I can see where a conversion of mph to km/h by redefining X mph signs to mean X km/h (ie speeds are reduced to 60% of their current values) would be in a situation where there is a simultaneous change from driving on the left to driving on the right. Should such a change take place, it would be appropriate from a safety point of view to reduce the speed limit during the change-over period. The logistics of such a change would be horrendous that I don’t see it ever happening.
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I suspect that a new government (or just a new Labour leader) would need to come into power with the goal of rejoining the EU. In that case converting road signs to metric only would be a perhaps smallish but still non-trivial signal to the EU of the sincerity and strength of its commitment to rejoining.
Ezra aka punditgi
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I am both pro-Metric and pro-EU but I do believe that the two issues need to be kept completely separate; I do believe part of the reason metrication has been so hard is because of a vocal minority equating it with ‘meddling from Brussels’, even with the factor that more and more are realising Brexit was a big mistake linking the two could be counter productive and the fact that Britain was trying to go metric well before the EU even existed should continue to be a campaigning point.
As to just adding ‘km/h’ to existing speed limit signs I also think that is a bad idea. Again you have the vocal minority who dislike any reduction in speed limits and would see a backlash. On the other hand metrication of speed limits alongside a sensible review of how some could perhaps be raised and others lowered would work for both sides of the argument.
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Everything I have read pretty much talks about how much of a challenge it will be to convince all member states of the EU to let the UK back in.
I suspect another referendum with a strong majority in favour of rejoining will be a vital step in the process. But harmonising with the EU road signage also sends a good signal.
Besides, if a strong majority vote in a referendum to rejoin the EU, metricating road signs will not spark a backlash with those very same folks; maybe even a fair bit of satisfaction. In the meantime the whining minority against all of that will always … well … keep whining.
Ezra aka punditgi
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