Speed limit arithmetic

[igenlode]

"It took an average of three minutes and 38 seconds to drive one kilometre (0.6 miles) in the centre of London last year... This was partly blamed on widespread 20mph speed limits" -- *what*?

20mph is 32km/h (using the rule-of-thumb conversion ratio of 5:8). So if you were travelling at 32 kilometres per hour it would take (60/32)=1.875 minutes to cover one kilometre: 1 minute 52 seconds. Clearly the majority of the time spent driving in central London is already spent travelling at speeds far *lower* than 20mph; probably spent stationary in traffic jams consisting of other cars. So just how fast are they expecting drivers to sprint between traffic jams in order that increasing the maximum speed limit will reduce journey times?

Comments

[pangolin20]

I think I've seen using more brackets for a smiley in English, too (though it seems to be used more for an ironic smile? I don't have any concrete examples, so I can't say), so this usage won't surprise me now, I think. Having looked up your examples, I can now also see why you'd find the closing bracket weird; it might well cause confusion with a double bracket for a double smile for me, at least. And it's nice to meet someone else who's as fond of using parentheses as I am!

Thanks for the information on these people and for the links!

Odd, there aren't any videos in the version in my browser. There are a lot of graphs, though!

(Oh, there are a couple of links to MP4 files at the end; I just assumed those did in fact illustrate the conclusions they were said to illustrate.)

Ah, that was what I referred to; because these links are put in a paragraph with other text, I considered it as directly part of the article (and they do support the conclusions, as far as I can tell).

That summary fully lines up with what I've seen for myself, so it's nice to have that confirmed by an actual study!

I've never been to a city as large as London, so it's interesting to know what it's like there (which is mostly "very busy", it seems! Ambulances usually get through where I've been). As for merging, I mostly based that off what I've seen on motorways, though there are some two-lane roads in cities I know, like Amsterdam, so I suppose it could be relevant there, too. And it seems I've learned a new word with "pannier", so that's nice to have.

[igenlode]

London has been very busy by all accounts since the Middle Ages - the nature of the vehicles in the traffic jams just changes :-)
But multi-lane roads tend only to exist where houses have been knocked down in order to create them - or else you have a compromise with two lanes in one direction and one in the other, or an extra lane when approaching a junction.
This is a fairly representative view of Central London streets and traffic speed (note supplementary bike lane at the start to allow the cyclists to pass :-D) These would originally have been considered extremely spacious streets when constructed, and if you see them without cars on a Sunday morning you can see that they still are.
The main roads where I live are narrower...

[pangolin20]

Good to know! Looking at some pictures of those streets, they're indeed rather wide for a city centre... I think I only just realised that, even though London is a rather large city, its centre is still the same thing as the city centres I'm familiar with, which makes the congestion much more intuitive to me! A contributing factor is probably that old city centres in the Netherlands are considerably smaller than London's, and that they don't generally have the equivalent of A-routes running through them.

The main roads where I live are narrower...

They probably are where I live, too (though that's partly because most of these roads don't have anything next to them), which further helps to put this into perspective!

[igenlode]

London is weird because it is basically a collection of villages that got merged/swallowed up, each of which has its own original centre; the very middle consists of what were originally two neighbouring cities separated by open countryside, the City of London (St Paul's Cathedral) and the City of Westminster (Westminster Cathedral) -- the English definition of 'city' being 'a town with a cathedral in it'!
So it has *lots* of 'old city centres' on a relatively small scale, rather than one big central area surrounded by suburban housing: places like Chelsea or Hammersmith were originally entirely separate settlements upstream.

But then there was bombing, and clearances to build new roads (most notoriously the Great West Road in Hammersmith, which is a 1960s American-style multi-lane flyover that blights its surroundings: https://metro.co.uk/2025/10/09/unpleasant-hammersmith-flyover-torn-replaced-a-tunnel-24380426/ )
There are still some of the old medieval streets left near St Paul's, but they are just pedestrian alleys, often covered over between office blocks, and not visible to cars.
https://theworkingline.com/secret-alleys-london-streets-hidden-passageways/

[pangolin20]

Thanks for all the new information, as I really didn't know that before now, and it's certainly good to learn more! For some specifics:

London consisting of multiple city centres makes more sense of its structure; I knew that the outer suburbs were once separate villages, but I hadn't considered it for the core, so I did find it weirdly large... and now I know what's causing that.

Yeah, I didn't even need to read the article to guess that it dominates its entire environment. Good to hear it might be replaced with a tunnel, though.

Nice that some of those streets have survived to the present day, even if they aren't obvious now; it's still a bit of history in a relatively accessible place.

[igenlode]

'Pannier', of course, is pure French (panier, basket) -- presumably in the days of our Norman French overlords panniers were originally pairs of baskets slung across the back of a beast of burden :-)
Later they became strong bags used for the same purpose, and nowadays the term is used by analogy for the luggage-bags (or hard boxes, in the case of a motorcycle; possibly those are more rigid because the extra weight is less of an issue with an engine to do the propulsion, or because if the machine falls or is laid down on its side they will get crushed) carried on the back of a two-wheeled vehicle.

[pangolin20]

presumably in the days of our Norman French overlords panniers were originally pairs of baskets slung across the back of a beast of burden :-)

And it's still used with much the same meaning, I see! (By the way, I see that "panier" comes from Latin "pannarium", which means "bread basket".)

Hmmm, it seems to be that they're more durable than soft ones, or that's what sites listing pros and cons of hard panniers tell me.

carried on the back of a two-wheeled vehicle.

Would it be idiomatic to call the bags on a bike that? (If so, that means I can equate it to an existing word in my native language.)