We’re big fans of the Essential Evidence series of one page summaries of peer-reviewed literature on current transport policies and practice. This is produced by Bristol based Dr Adrian Davis in order to ensure that academic research and evidence informs implementation of planning and policy. Although sadly one recent summary shows that politicians are far more resistant to this than professionals and communities (No 187: Examining the politics of transport planning). Summary No 185 is another confirmation of the robustness and effectiveness of the city-wide Bristol scheme, The effectiveness of a 20mph speed limit intervention on vehicle…
20mph speed limits on most streets and roads in Bristol has been one of Bristol Cycling’s campaigns (Twenty’s Plenty) from the beginning. We encouraged as many BCyC members as possible to respond to the consultation in 2018 (7 Reasons Einstein would support 20 mph) and we were pleased at the overwhelmingly positive response the council received. We put in our own formal submission as well, as below or click here Response to 20mph consultation 2018. Introduction The ability to cycle safely on low speed, low traffic streets is essential in providing a comprehensive cycle network in Bristol. In…
Bristol City Councils 20 mph review finishes today. In this consultation, the potential of 20 mph to help meet the National Air Quality Objectives (NAQOs) for NO2 and PM10 emissions, for which Bristol exceeds, has almost completely been ignored.
Instead, a Clean Air Zone (CAZ) has been proposed to tackle this as part of central governments Clean Air Framework. A CAZ would attempt to reduce air pollution by encouraging residents and businesses to purchase a cleaner car. A scrappage scheme has even been mooted as a way to kick-start this.
A CAZ might encourage some people to leave their car at home but it would have nowhere near the benefits of 20 mph limits.
One of the key infrastructure requirements for a CAZ is Auto Number Plate Recognition (ANPR) cameras. These are the same yellow cameras used along the M32 to enforce speed limits. They are one of the most effective measures for speed enforcement, ensuring drivers stick to the speed limits within the zone. Surely it would make sense to simply install these cameras to enforce the 20 mph speed limits that are already in place?
From Bristol Cycling’s perspective, 20 mph zones are only positive for Bristol. We recently highlighted the key benefits of 20 mph. In summary, 20 mph limits:
Reduce Collisions and lessen their severity when they do happen. A driver seeing a danger travelling at 30mph would have travelled 9 metres before they even pressed the brake pedal and another 14m to come to a stop. At 20 mph the overall stopping distance is half that. This makes a collision less likely in the first place. The kinetic energy of a 1419kg Nissan Qashqai car travelling at 20 mph is 15.7 Wh. If the vehicle didn’t stop in time, this would be the energy felt by the object it hits. Increase this speed by 50% to 30 mph and the kinetic energy goes up by 125% i.e. it more than doubles to 35.4 Wh. To put this in comparison, the energy of a 90kg cyclist at 20 mph is 0.9 Wh and a 70kg jogger at 5mph, 0.05 Wh. This video of an appalling collision in Wales demonstrates the huge amount of energy in a moving car.
A car braking from 30 mph to a stop puts more than double the energy through the brakes, tyres and roads than the same car stopping from 20 mph, increasing particulates (PM) from the brakes, tyres and road, contributing to poorer air quality. It also puts more strain on the road surface making damage and potholes more likely.
20 mph has also been shown to reduce noise from vehicles. A car travelling at 20 mph instead of 30 mph can emit almost 10db less noise. 10 db is perceived by the human ear to be a halving of noise. Studies in Sweden, Germany and the UK, have consistently found 2—5 db noise reductions at the roadside from 30 kph (20mph) limits.
20 mph Improves traffic flow and reduces journey time. Countless studies have found 20 mph reduces the concertina effect of traffic and reduces congestion.
Acceleration is the most energy-intensive stage of driving. Lower speed limits mean less time on the accelerator pedal and reduced fuel consumption. Considering a hypothetical a 16km journey with 25 stops and starts a car only accelerating to 20 mph will spend nearly a minute less on the accelerator than if it reached 30 mph. Although this does not directly correlate with emissions, a detailed study in London found (unenforced) 20 mph limits reduced NO2 air pollution concentrations at the roadside.
Over the past few weeks, Bristol Cycling has been campaigning hard to raise awareness of the 20 mph consultation. The criticism we hear time after time is that 20 mph isn’t enforced* and that “no one really travels at 20mph”. This isn’t a reason to scrap it, it is a reason to do it properly and see what the real benefits could be.
We’ve not heard anyone suggest the CAZ could be left to chance police patrols to enforce, so why has 20mph?
ACTION: Please take a moment to respond to the Bristol 20mph Review
Our lives fundamentally rely on energy. It puts food on our table, gets us to and from work, powers our offices and factories. The more we use, the more money it costs us. Our demand for it causes wars, our generation of it emits harmful gases.
Almost every issue 20mph raises is energy related and the answer to each, along with many of our urban challenges, can be found by looking for the lowest energy solution.
Energy dictates the severity of a collision, how much fuel is burnt to move somewhere and the volume of emissions that activity will release. The more energy we put through car components and the road surface the quicker they will break and wear out. The faster a vehicle moves the more noise it generates.
Yet energy is rarely mentioned. Despite apparent concerns over climate change and air pollution, sales of energy-hungry SUVs are soaring, up 24% across Europe this year and on course to become the most common cars on our roads.
So in this time of “fake news” and manipulation of facts, what better way to argue a case than with some basic physics. Just as keen cyclist Albert Einstein might have done. Here are the seven reasons (also as an infographic here):
Bristol are consulting on 20 mph speed limits in the city (20mph Limits Review). We believe the city-wide ‘Total Twenty’ approach has been good for walking and cycling, and the evidence supports this. We’re concerned that the review seems to be wholly focussed on reversing this and allowing 30mph on many roads. There is almost no mention of eduction or enforcement measures to embed the change. We’re asking everyone to respond to the review. There are suggestions below to make it quick and easy. The exercise has benefitted from a UWE Monitoring Report which has found that Bristol’s 20…
Last month a review of Bristol’s 20mph areas was published by UWE with coverage in local media (here, here and here). This adds to the growing weight of evidence backing city-wide lower speed limits (unlike a widely ridiculed ‘report’ from Bath and North East Somerset Council (BANES). UWE’s Bristol Twenty Miles Per Hour Limit Evaluation (BRITE) study found that, on average, speeds on more than 100 surveyed roads have reduced since the 20mph speed limits were implemented, with average speeds of between 19mph and 26mph on 20mph roads shown in the report. On 30mph streets,…
One of those lives saved could have been yours or a loved ones. We’ve campaigned for 20mph to be the default speed limit in Bristol for nearly 30 years and we welcome this report from UWE which also found an estimated cost saving of over £15m per year from the avoidance of fatal, serious and slight injuries. So why is Bristol City Council still forging ahead with a review of the 20mph rollout, when clearly it has been an outstanding success? Former transport chief Mark Bradshaw (Labour) tweeted “No doubt local changes needed with more enforcement action – but…
On Wednesday 10 January, BBC Two aired Fighting for Air, a documentary looking at how a local community in Birmingham, aided by a BBC team, set about tackling pollution on their local high street. The street could have been a number of shopping streets in Bristol, with almost identical debates on issues involved. The solutions put forwarded for reducing pollution were smoothing traffic flow by introducing green waves, replacing the parking bays with vegetation and handing out free bus tickets. The natural reaction of some of the…
It’s good to see yet another new report about the popularity of 20mph limits, this one from UWE academics published on the Bristol Health Partners website: Seven in every 10 adults in Great Britain support the introduction of 20mph speed limits in busy streets, according to a major new survey.The poll conducted by YouGov earlier this year found 72 per cent of the 3,000 respondents backed the limit in busy streets, with 21 per cent in opposition. The result mirrored findings from similar online surveys carried out as part of the same study in 2013 and 2015. The…
The 20mph debate rages on in Bristol, with murmurings of potential reversal, Bristol Cycle Campaign want to shed some facts on an important aspect – Energy and Emissions. We’ve even got a handy infographic.
One controversial argument often heard is that a vehicle travelling at 20mph has higher fuel consumption and emissions than at 30mph. Whilst it is true that the gearing on most passenger cars means that traveling on an empty motorway at 20 instead of 30 would use more fuel for the same distance, the same is not true in urban areas. Even during uncongested times these roads have junctions and traffic lights. It is almost impossible to safely navigate a city without stopping and starting.
Take a 4km journey with 7 stops 500m apart.