this post was submitted on 16 Sep 2023
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The Conservatives in Wales lose their last ditch attempt to stop the speed limit change from 30mph to 20mph. The change will be coming into force on the 17th September

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[–] [email protected] 13 points 1 year ago (2 children)

It's still not the right way to go about it. If you want to make a 20 mph road, then build a 20 mph road - complete with traffic calming measures, as per the official recommendations. Just slapping a 20 sign on a road that feels like a 30 is only going to increase noncompliance (currently measured at ~85% for 20 roads). That's not to mention traffic light systems that have been timed to 30 mph roads, these are never updated when the speed limit changes.

If you want people to change how they drive, then they need training, not altered roads. Hell, even just doing your ROSPA and IAM isn't perfect, because if you don't keep up your training you'll develop bad habits over time.

this speed limit change will not hinder progress in built up areas.

Big assumption, one that doesn't hold up. Travelling at 20 mph takes 50% longer than travelling at 30 mph.

It will definitely save lives

Possibly, in a select few areas. These areas should be identified and addressed properly, which may well save more lives.

and reduce pollution

The difference in fuel consumption between driving at 20 and 30 is negligible. The main economy difference is acceleration, and slowing down and accelerating for 20 areas increases fuel consumption. Hell, the government white paper on speed bumps mentions higher fuel consumption leading to fuel tax revenue as a benefit.

In heavier traffic, ruzh hour, it will make not difference.

Probably not, but that's not the concern here. The concern is about impeding progression when there is no traffic and no good reason, ie an empty road through town in quiet times with few cars or people about.

I'm sure there are some areas that will benefit from a reduction to 20 limits, but a blanket change from 30 to 20 is just poorly thought out political pandering.

[–] [email protected] 14 points 1 year ago (1 children)

The concern is about impeding progression when there is no traffic and no good reason, ie an empty road through town in quiet times with few cars or people about.

The thing is, nobody plans to crash their car into a pedestrian. So how does it keep happening? One reason is from people driving faster than they should because they wrongly believe a road is empty. Slower limits help with this, because when drivers are going around with incorrect beliefs about whether roads are empty or not, there is more time to react and less energy to cause injury

[–] [email protected] 8 points 1 year ago

I can't disagree with anything that you're saying here. All I can say is that there is always a balance to be struck between road users - pedestrians, cyclists, cars, everyone (even animals).

So how does it keep happening?

It happens because road users aren't properly segregated. If you look at large construction sites, they have barriers everywhere and it's generally extremely safe. They still have fatal accidents between vehicles/plant and people. The only way to be completely safe is to be separate - but that isn't reasonably practicable everywhere.

My issue here isn't with 20 mph roads. My issue is with a blanket change of all 30 mph roads to 20 mph, without making those roads suitable for 20 mph. Maybe some of these roads already should be 20 mph, but many aren't and shouldn't be, and the ones that aren't will encourage further noncompliance everywhere else.

[–] [email protected] 1 points 1 year ago (1 children)

You can do the maths to work out percentages of a small number. Perhaps check the killed and seriously injured specs, and whilst online, the other technical assessments. Give me more than uninformed view to consider.

[–] [email protected] -2 points 1 year ago (1 children)

I can do the maths, but apparently you refuse to. You're going by what you've been taught about speeding on the motorway, how 80 mph is really very close to 70 mph in terms of time. That doesn't hold true between 20 and 30.

You're not considering anything, you're not arguing the points I've presented, you're just trying to fight me. It isn't working.

If you have evidence that backs up your side of the argument then please present it, like I have with the government's compliance statistics. Don't try to pass off the work for making your argument onto me.

[–] [email protected] 2 points 1 year ago (1 children)
[–] [email protected] -2 points 1 year ago* (last edited 1 year ago) (2 children)

So their key points:

  1. Drivers cut their spacing as braking distances contract. Shorter gaps mean more vehicles can use the available road space, reducing standing traffic.
  2. Filtering at junctions becomes easier too. It is far easier for motorists to pull into traffic travelling at 20mph than at 30mph. So junctions work more efficiently and queues reduce.
  3. Motor traffic volumes decrease since slower speeds encourage active, sustainable and shared travel. Walking and cycling levels rose by up to 12% after Bristol’s 20mph limit[i].
  4. Buses operate more efficiently. The reduced length of queues means that bus journey times decrease, and become more reliable. Buses become a more attractive alternative to the car.

Don't really relate to 20 all that much.

  1. The space in distance between moving traffic is irrelevant, the following distance expressed as time will always be the same (~2 seconds). The space between stationary traffic is the same in both 20 and 30 zones.
  2. Filtering isn't about speed, filtering is about technique. It's about restraining your acceleration and leaving a bigger gap in front. It can be done at any speed - it's what you do when entering a motorway at 70 mph. Reducing the speed limit does not teach people how to filter.
  3. Bristol is a city, this post is about Wales as a country adopting 20 mph limits. I live near Bristol, and many Bristol roads need to be 20 - they're too narrow and there's too much going on (and that's not to mention the potholes..). That isn't true elsewhere in the UK, and certainly not throughout the countryside, even the countryside immediately outside of Bristol. However, even with the 20 limit, many of the roads in Bristol are not built suitable as 20 mph roads, and compliance in these areas is very low. Even buses do 30 in these places.
  4. The efficiency improvement for buses is negligible. Drivers let buses out. Again, this incorrectly attributes reducing speed limits to training drivers how to filter and how to drive in traffic.

If you want 20 mph roads, then build 20 mph roads. If you want drivers to drive better, train them.

[–] [email protected] 3 points 1 year ago (1 children)

Just in general, can I ask what you're hoping to get from this thread? I mean, you're in the Fuck Cars community asking everyone to agree with you that today's driving is okay, that there aren't benefits from slowing down motor traffic and that we shouldn't expect people to act legally. It seems a strange battle to choose.

[–] [email protected] 1 points 1 year ago

I'm just calling out bullshit political pandering in a blanket speed limit reduction as what it is: bullshit political pandering that doesn't even really achieve the goals it sets out to do.

I'm not against 20 limits, I'm not against increasing safety of vulnerable road users, I'm not against reducing the use of cars. I want those things to be done appropriately and effectively. This is not that.

[–] [email protected] 0 points 1 year ago (2 children)

That whole study is specifically aimed at 20mph. It does reduce speed but not exactly by 10mph. It’s going to reduce traffic time, casualities, pollution and increase walking and public transport use.

There is a lot to like and for the places that it doesn’t apply people can always put up a sign for 30. Ideally this is supported by traffic calming measures but that’s a longer more costly.

[–] [email protected] 2 points 1 year ago

Also, if you want to refer to that blog post as a "study", we should look only at its sourced claims.

  1. Motor traffic volumes decrease since slower speeds encourage active, sustainable and shared travel. Walking and cycling levels rose by up to 12% after Bristol’s 20mph limit [^1]

This is specifically about Bristol, a city with narrow roads.

  1. Smoother driving with less wasteful braking and acceleration cut fuel use by 12% in Germany after 30kmph (18.6 mph) limits were implemented [^2]

I'm sure Germany have implemented speed limits efficiently, but the UK has a history of compelling local councils to implement traffic measures that increase fuel consumption and thereby increase fuel tax revenue. Regardless, Germany have not changed all of their 50 kph zones to 30 kph, like this law proposes.

  1. The Department for Transport’s speed / flow plots are in the COBA (Cost Benefit Analysis) manual - Vol 13 of the Design Manual for Roads and Bridges. This computer programme shows that urban traffic flow improves at lower speeds [^3]

Urban traffic flow. This law covers everywhere.

  1. The FREEFLOW project by the University of York, City of York Council and others... Slough experimented with this successfully in the 1950s on a single arterial road. [^4]

This experiment was from 1950.

  1. Shared Space also enjoys claims of shorter tailbacks and congestion. The concept relies on cutting traffic speeds to around 20mph or less for ‘eye contact’. Traffic experts Ben Hamilton Baillie and Phil Jones state "tailbacks of traffic during peak periods have also reduced. It seems that the ambiguous junction provides improved capacity for traffic and fewer delays than traffic signal control systems." [^5]

Urban design, referring to handling specific zones of congestion.

None of these points apply to changing the national speed limit for Wales from 30 to 20.

[^1]: Cycling City project and Active Bristol / Monitoring by Bristol City Council http://www.betterbybike.info/sites/default/files/attachments/Cycling%20City%20end%20of%20project%20report.pdf [^2]: An illustrated guide to traffic calming. by Dr Carmen Hass-Klau (1990) [^3]: Link to a copy of the COBA 2002 manual – Traffic Flow plots are in Chapter 9: http://www.leics.gov.uk/part_5.pdf [^4]: http://www.freeflowuk.net/index.php?option=com_content&view=article&id=73&Itemid=59 [^5]: Improving traffic behaviour and safety through urban design. Proceedings of Institute of Civil Engineering. Ben Hamilton Baillie, Phil Jones May 2005 http://www.icevirtuallibrary.com/content/article/10.1680/cien.2005.158.5.39

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[–] [email protected] 2 points 1 year ago

If they put up a ton of 30 signs then it probably would be alright. Eg, the main road through a village or town could stay 30, while the main high street and side roads would all be default 20. But that requires more than just a change in law to say "what was 30 is now 20", and they don't seem to be doing this. They're expecting financially strapped local councils to go through a process of assessing and assigning 30 limits themselves, at their own expense. It likely won't happen in most places, they simply can't afford it.