How to make safety decisions - Wales urban 20mph

[monkey]

U.S. speed limits ending in 5 are just as common as those ending in 0. Anything between 25 and 70 is pretty normal. Less than 25 is rare. More than 70 is rare and only possible in some states.

My impression is that ending in 5 is more common than ending in 0. I'd say that 30 is less common than 25 and 35 around here. 40 and 50 are rarer than 45, 55 is the default for dual carriageway and A-road equivalents, plus motorway equivalents in built up areas. 60 is pretty much nowhere, and some big highways are 65.

There's a push for more 20 mph zones in dense cities here as well. 15 mph isn't uncommon in airports, parking lots, etc.

Here the state limits* all end in 5, apart from the interstates (70 mph). When they're lower (for safety or noise reasons) it's usually by 10 mph increments, but not always. The lowest limit is 15 mph outside schools. But that's only used when the school is on a busy road and during hours.

I have wondered before if the ending in 5 thing was because the national limit was set at 55 mph during the oil crisis. That was an economic choice rather than a safety one.


*It often feels like most drivers think these are guidelines, mind.

[dyqik]

Schools up here are typically 20 mph limits.

And the average speed here is typically the speed limit +5mph + 15-20%

[Gfamily]

I noticed on a recent trip through Spain and France that they have different ranges for their limits.
France is almost exclusively the Odd 'Tens': so 30 (restricted urban), 50 (urban) 70 (hazardous rural), 90/80* (rural), 110 (dual carriageway), 130 (autoroute)

Whereas in Spain we saw 20,30,40,50,60,70,80,90 limits. I think I might have seen a 25 at one point

It was interesting that in France, towns often have a chicane or a speed bump with 30 kph limit as you enter and leave the town, whereas in Spain there will sometimes be a set of traffic lights as you enter a town that'll be triggered if somebody is going faster than 50 kph.

* AIUI, a few years back Paris imposed a 'standard' 80kph limit on rural roads, but some departments have exercised their authority to increase their limits back to 90 (I seem to recall it was previously 100kph (similar to UK National Speed Limit).

[FlammableFlower]

About to vibe to the end of our French road trip. On the way down to Mâcon from the tunnel we decided to avoid the payage so took all the smaller roads. There are a lot of towns and villages with 30kmh limits, and, as Gfamily did, they're generally marked by speed bumps (often very high and steep!), do you definitely have to show down for them. It's getting to the point where it's the majority we've driven through.

Most rural roads (white sign background) are now 80kmh.

[Sciolus]

People are talking about imposing costs on motorists in order to provide benefits to third parties. In fact, we are redistributing a fraction of the costs that motorists impose on third parties back onto the motorists. That seems rather harder to argue against (without going "waaaah, road tax!!11!").

But the motorists and the third parties are almost the same people.

No, because:

We don't need to ask people, because we already vote with our money. Collectively we pay a premium to live in a quiet cul-de-sac. And pay a discount to live on a busy road.

the people who live on roads that are both heavily-trafficked and have dense houses along them are considerably poorer than average and drive less than average. There is a strong social equity issue behind this policy.

Evidence (albeit for England rather than Wales):

• Minoritised ethnic groups experience higher [air pollution] emissions regardless of deprivation.
• Minoritised white ethnic groups experience higher emissions than the majority white.
• All major sources contribute to emissions disparities.
• The consistency of emissions disparities suggests environmental injustice.

All 24 minoritised ethnic groups studied experienced higher average local NOx and PM2.5 emissions than socio-economically matched populations in the majority ‘White: English, Welsh, Scottish, Northern Irish or British‘ ethnic group. Chinese, Arab and Bangladeshi communities experienced the largest disparity in NOx, with weighted emissions 100%, 91%, 89% higher than white populations of matched deprivation status. Bangladeshi, Pakistani and Roma groups experienced on average 40%, 40%, 36% higher PM2.5 emissions locally than matched white groups. For NOx the largest contributors leading to disparity, were road transport (48%), domestic combustion (23%) and industry (15%). For PM2.5 the greatest contributors to disparity were domestic combustion (53%), road transport (19%), and industry (11%). Living near to road transport and in city centres are frequently cited as primary drivers of ethnicity and deprivation-based disparities, however the analysis identifies that industrial, domestic and off-road sources create issues of the same magnitude, and disparities remain in suburban settings, smaller towns and some rural areas.

tl;dr: You can't talk about this without talking about race and poverty.

[Sciolus]

There was some fairly peripheral discussion of the other benefits of the policy in reducing external costs, but since I'm dumping evidence here to be ignored, here's some more:

• According to the latest Environmental Noise Directive (END) reporting, over 20% of Europeans — more than one in five — are exposed to harmful transport noise levels. When measured against stricter World Health Organization (WHO) recommendations, this figure rises to over 30%, or nearly one in three citizens.
• Road traffic is the most widespread source of transport noise, exposing an estimated 92 million people to levels above the END threshold of 55 dB for the day-evening-night period, compared to 18 million affected by rail traffic and 2.6 million by aircraft noise.
• When compared to other environmental health threats, transport noise ranks among the top three — just behind air pollution and temperature-related factors. Chronic exposure to noise from transport contributes to 66,000 premature deaths annually in Europe, while also leading to around 50,000 new cardiovascular disease cases and 22,000 cases of type 2 diabetes.
• Almost 16.9 million Europeans experience long-term annoyance due to noise from transport and approximately 4.6 million suffer from severe sleep disturbances. According to new research, noise could also contribute to thousands of cases of depression and dementia.
• It is estimated that over half a million children in Europe experience reading difficulties and about 63,000 experience behavioral issues due to transport noise. High noise levels are also linked to approximately 272,000 cases of overweight children.
• Noise pollution from transport sources results in the loss of 1.3 million healthy life years annually in Europe, equivalent to an annual economic cost of at least EUR 95.6 billion, representing around 0.6% of the region’s gross domestic product (GDP) each year.
• Based on current projections, it is unlikely that the EU will meet the target set out in 2021 EU action plan ’Towards zero pollution for air, water and soil’ to reduce the number of people chronically disturbed by transport noise by 30% by 2030 (compared to 2017 levels) without additional measures, including regulatory or legislative changes. The number of people highly annoyed by transport noise in the EU declined only by an estimated 3% between 2017 and 2022, falling short of the pace needed to meet the zero-pollution noise reduction objective.

And specifically on reducing speed limits to 20 mph:

Quantifying the potential impact of reducing urban speed limits from 50km/h to 30km/h
in Europe

A study by the City of Zurich and the Federal Office for the Environment in Switzerland
found that reducing speed limits in Zurich from 50km/h to 30km/h led to a decrease
in the average noise levels — 1.6dB during the day and 1.7dB at night (Stadt Zürich,
Umwelt- und Gesundheitsschutz and Bundesamt für Umwelt, Abteilung Lärm und NIS,
2022). However, the reduction in perceived annoyance and sleep disturbance was even
greater, corresponding to 2–4dB for annoyance and around 4dB for sleep disturbance.
This suggests that lower speed limits not only reduce noise but also enhance perceived
safety and neighbourhood liveability, potentially improving residents′ reactions to noise
intervention (Brink et al., 2022). Based on these findings, additional health benefits — such
as improved mental and cardiometabolic health and fewer premature deaths — may also
be expected (Rossi et al., 2020).

Applying these relationships at a European scale, residents living near roads with a
speed limit of 50km/h in urban areas could see a 30% reduction in baseline annoyance
if the speed limit is lowered to 30km/h. Similarly, sleep disturbances could decrease by
approximately 40%. Assuming that around 30% of urban roads currently have a speed
limit of 50km/h, the potential overall impacts could lead to a 9% decrease in the number
of residents reporting high levels of annoyance and a 12% decrease in those experiencing
high sleep disturbances. When considering the entire population currently affected by
road traffic noise in Europe, this translates to a 7% reduction in highly annoyed (HA)
individuals and a 12% reduction in those suffering from high sleep disturbances. These
reductions may vary significantly depending on various factors including the local context,
the infrastructure, the types of vehicles and also baseline noise levels.

[IvanV]

A colleague of mine, then a professor of Economics at Cambridge University, deliberately bought a house on a busy arterial road in Cambridge. There was a large discount on a house of those dimensions and quality for its unhappy location. He reckoned that by retrofitting it with highly sound proof windows and mechanical ventilation he could get a lot more house for his money, and not have to suffer noise. He did that, and reckons it worked very well.

Unfortunately most of our towns and cities were laid out in the days of horse-drawn transport, and indeed travellers on foot, when passing traffic was considered a benefit in terms of an economic opportunity, rather than a nuisance in terms of noise. Not helped by 1960s (ish) town planners building urban dual carriageways everywhere in certain cases. Bypasses help, where they have been built. But their typically remains a requirement to move large travelling populations into the town for business and habitation.

And the nonsense of building new housing estates right up to the edge of the by-pass continues, despite thus exposing those populations to noise. Though, of course, those houses are cheaper, and that is kind of a benefit to the poor - they trade their exposure to noise for a cheaper house.

So, in principle, there are other solutions to noise disturbance than slowing roads down. Doubtless the ideal is a mix suited to location. Which is fortunate, because we can't slow every road to 20mph that runs near dwellings. But it is also unfortunate, because it requires investment in the building, and the people who are most affected are the less well off who are less able to afford that, or their landlords to afford it. In an urban situation, a move to EVs will make a considerable contribution to noise reduction. But at higher speeds, tire noise dominates, and in fact EVs are noisier on high speed roads because they are heavier.

[Anecdote]
Shortly after I moved to this area, there was a bit of a planning battle over a field a few miles away that a gypsy/traveller type put a static caravan on. Eventually they won planning permission for a small estate of about a dozen static caravans on that small field. When it was just that one caravan, they made it very pretty and tidy. Today you can see the rubbish piles, which form a bank entirely surrounding the site, on google earth. They have just the same rubbish collection service as me. But the notable feature of the site is that it is right next to the M25. It's not good for people to live right next to the M25 in poorly sound insulated static caravans. But that's seemingly what they wanted. If we deny it, that is doubtless some discrimination against a disadvantages population that wants to live at low cost. So we see economically disadvantaged people seemingly deliberately choosing to site themselves right in about the noisiest place possible. And then some time later, for added annoyance to the residents, it turned out their site lay almost directly on top of the HS2 tunnel portal, albeit separated from that worksite and hole by the width of the M25. Whether the annoyance they suffer from that is only during construction - it is a massive construction site and I think the crossing of the M25 and continuation of that road on that side is closed for the duration - or whether they will additionally hear some loud sonic whoosh as trains enter the tunnel, perhaps in about a decade's time, I don't know.
[/Anecdote]