Vehicle Speed Compliance Statistics, Great Britain: 2018

[whitenemesis]

An interesting little read...

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/812500/vehicle-speed-compliance-statistics-2018.pdf

 

[Dryce]

An interesting little read...

That's really interesting.

Simple conclusion - 20mph limits are a joke.

One aspect I think distorts this - the qualification of 'free flowing'. My guess is that the majority of vehicles on the motorways don't experience this condition - because the 'free flowing' aspect requires low density. So the graphs suggest a lower level of compliance than actually takes place in the real traffic conditions experienced by the majority of road users.

 

[whitenemesis]

I think the section "Understanding and Interpreting these statistics" explains the limitations. Free Flowing doesn't refer to the actual movement of traffic but the freedom from external factors such as speed cameras and junctions etc..
Data is obtained from sensors reading traffic in "real traffic conditions experienced by the majority of road users."? 655 million vehicles were used in the 2018 data. Data is discounted during times when traffic volumes are abnormally low or high..

 

[markjay]

Simple conclusion - 20mph limits are a joke.

I echo that.

Down here in London, when driving at 20mph in a 20mph zone, I have had cars behind me flash their headlights, sound the horn, and even overtake. I find driving 20mph in a 20mph zone more stressful than doing 30mph in a 30mph zone.

 

[bolidemichael]

I echo that.

Down here in London, when driving at 20mph in a 20mph zone, I have had cars behind me flash their headlights, sound the horn, and even overtake. I find driving 20mph in a 20mph zone more stressful than doing 30mph in a 30mph zone.

20mph should be 25mph for a 'flow' to develop. On a wide road on a clear evening, it's an insult to attentive drivers.

 

[markjay]

The 20mph in London was done to reduce pollution and improve pedestrian safety (and, as pedestrian, I have to agree).

But not in order to improve traffic flow or reduce congestion - quite the opposite, in fact: TfL closed down many side roads to traffic, and removed lanes from many main arteries, in addition to local councils increasing the cost of parking - all in order to make the city as unfriendly as possible for car users.

And as much as it's inconveniencing me personally, I have to say they do have a point.

 

[Dryce]

Data is obtained from sensors reading traffic in "real traffic conditions experienced by the majority of road users."? 655 million vehicles were used in the 2018 data. Data is discounted during times when traffic volumes are abnormally low or high..

Trouble is I don't believe that the majority of traffic goes over 70 on the motorway. I don't see it on the journeys I make across the country.

So if you drive the M6 between Lancaster and Carlisle - then the proportion is higher *but the number of vehicles is lower* whereas say south of Preston lots more traffic and the majority below 70. At times when you see more people going faster there are few cars.

The comment about lexcluding data from roads where there are enforcement cameras increasingly exludes the busiest sections of motorway and smart motorways.

So I suspect the motorway figures are not meaningful. And the same is probably increasingly true for significant trunk routes.

 

[whitenemesis]

But the data shows the majority (54% to be precise) of motorway drivers travel at or below 70 mph?

I'm struggling to understand your arguments over the data when your points have been covered and explained within the document. It recognises the deficiencies in some of the data and recognises areas of inaccuracy.
The speed compliance is also shown against time of day and clearly graphs the increase in speeds outside the busy periods.

 

[190]

The 20mph in London was done to reduce pollution and improve pedestrian safety

Pedestrian safety from impact is undeniably improved but I suspect in common with all "traffic calming" measures, one thing a 20 mph limit vs a 30mph limit doesn't do is reduce pollution. Vehicles will have to engage a lower gear, use more fuel and produce more pollution. We have 20mph limit through our village with speed humps and most vehicles accelerate then brake between each hump. Councils have been advised by government that traffic calming measures may increase pollution but I haven't seen any speed humps being removed.

The Impacts of Traffic Calming Measures on Vehicle Exhaust Emissions.

 

[SW18]

Very interesting report, thanks! 20mph zones don’t appear to be a total waste of time, if I read the data correctly. For cars it shows that 78% of cars in a 20 zone were recorded at under 30mph, whereas only 34% of cars in a 30mph zone were under 30mph. I’ve always supposed that 20mph zones are about keeping most cars under the magic 30mph point, above which impacts with pedestrians have a much more serious outcome (there is plenty of research on that).

I too see a minority of drivers who are actively aggressive towards those trying to comply with 20mph limits. We’ve had 20mph limits on most streets here for several years now, and I find that 25mph is a sweet spot: quick enough that most following drivers are ok with it and don’t get annoyed; slow enough to comply with at least the spirit of the rules. In fact 30mph on urban roads now feels a bit fast to me as I’ve adjusted my pace downwards; 25mph gives more time to read the road conditions properly, which is surely good practice in urban driving where there are a lot of data points to observe.

 

[Deleted member 65149]

I don’t know of anywhere that 20mph zones/limits have been introduced as a pollution reduction measure. It’s all about pedestrian safety and attempts to encourage a healthier more active lifestyle.

One of the major objections cited against 20mph zones/limits is that pollution levels increase, particularly where the limit is paired with speed humps. The truth, however, is different: Imperial University’s evaluation of 20mph zones in London suggested they had no net negative impact on exhaust emissions and resulted in clear benefits to driving style and associated particulate emissions. Remember that particulate emissions aren’t limited to those from exhausts, but includes tyre and brake wear.

An early study (there must be something newer) concluded that 20 mph zones are effective measures for reducing road injuries and deaths.

“The introduction of 20 mph zones was associated with a 41.9% (95% confidence interval 36.0% to 47.8%) reduction in road casualties, after adjustment for underlying time trends. The percentage reduction was greatest in younger children and greater for the category of killed or seriously injured casualties than for minor injuries. There was no evidence of casualty migration to areas adjacent to 20 mph zones, where casualties also fell slightly by an average of 8.0% (4.4% to 11.5%).”​

Effect of 20 mph traffic speed zones on road injuries in London, 1986-2006: controlled interrupted time series analysis

Objective To quantify the effect of the introduction of 20 mph (32 km an hour) traffic speed zones on road collisions, injuries, and fatalities in London. Design Observational study based on analysis of geographically coded police data on road casualties, 1986-2006. Analyses were made of...

www.bmj.com

I live in the middle of a 20 mph zone and I have no problem with it whatsoever. I can cope with losing those few extra seconds my journeys may take.

 

[SW18]

I live in the middle of a 20 mph zone and I have no problem with it whatsoever. I can cope with losing those few extra seconds my journeys may take.

My thoughts exactly.

 

[190]

One of the major objections cited against 20mph zones/limits is that pollution levels increase, particularly where the limit is paired with speed humps. The truth, however, is different: Imperial University’s evaluation of 20mph zones in London suggested they had no net negative impact on exhaust emissions

That's in contradiction to the study I linked above on traffic calming measures.

For petrol non-catalyst, petrol catalyst, and diesel cars, mean emissions of CO per vehicle-km increased by 34 per cent, 59 per cent, and 39 per cent respectively

For all three vehicle categories the increase in mean HC emissions was close to 50 per cent.

Emissions of particulate matter from the diesel vehicles increased by 30 per cent.

Which experts can you believe. My observation of traffic calming with speed humps leaves me in no doubt that emissions rise as a result. The only way they could not rise is if vehicles were able to cruise through the zone on no throttle and the only chance that could happen is if they left out the speed humps.

 

[Deleted member 65149]

Which experts can you believe. My observation of traffic calming with speed humps leaves me in no doubt that emissions rise as a result. The only way they could not rise is if vehicles were able to cruise through the zone on no throttle and the only chance that could happen is if they left out the speed humps.

My apologies, I said no increase in exhaust emissions when I should have said no increase in pollutio.

Speed humps within 20mph zones only lead to increased exhaust emissions when drivers fail to observe the limit and drive badly: accelerating and braking between each hump. I can set my cruise to 22mph and drive all the way through the zone where I live without touch the throttle or brake pedals.

 

[bolidemichael]

With my cyclist's chapeau on... 20mph on a flat road is ideal for keeping up with the flow of traffic on my commute and maintain a safety bubble, as I position myself defensively to the right of the middle of the lane i.e. the position that I would adopt had I been sat on a heated seat in a RHD vehicle. Swings and roundabouts... the downside is that in low traffic density situations, very few respect 20mph as it is far too slow and therefore the expectation mismatch between the speed that another road user (a more vulnerable one) anticipates and the actual speed adopted is an even wider gulf.

 

[st13phil]

the downside is that in low traffic density situations, very few respect 20mph as it is far too slow and therefore the expectation mismatch between the speed that another road user (a more vulnerable one) anticipates and the actual speed adopted is an even wider gulf.

This is a very real issue and one that has shown up in other studies when accident rates have actually increased after the introduction of 20mph limits.

It neatly illustrates why "lowest common denominator" legislation is rarely as effective as the trial scenarios that are used to justify its introduction indicate. Oddly enough, the majority of drivers can successfully select a driving speed appropriate to the conditions without regulation, which is why setting limits at the 85th percentile speed for free-flowing conditions worked well for decades and also resulted in good levels of compliance without resort to continuous enforcement. The shift to setting limits at the median speed for free-flowing conditions has lead to a general lowering of limits (most noticeable is the shift from NSL to 50mph limits on single-carriageway roads) which are then widely ignored absent enforcement.

 

[Tonygw]

Personally I have always thought that reducing speed limits to protect pedestrians is a bit of a nonsense?

Surely to protect them/us they should make the paths better, and make it more difficult to step out onto the road. Give them/us better allocated safe crossing areas. The fact that most people walk along these days looking at their phones rather than where they are actually going is good enough reason to improve foot ways etc, don't encourage pedestrians and vehicles to mix, its a recipe for disaster.. even at 20mph.

In an industrial environment, where blocks of 1 ton steel were wizzing past at 20/30/40mph do you think it would be allowed for the general public to walk less than 30cm from the moving objects?? No me neither but it seems we accept this in normal life.

 

[bolidemichael]

This is a very real issue and one that has shown up in other studies when accident rates have actually increased after the introduction of 20mph limits.

It neatly illustrates why "lowest common denominator" legislation is rarely as effective as the trial scenarios that are used to justify its introduction indicate. Oddly enough, the majority of drivers can successfully select a driving speed appropriate to the conditions without regulation, which is why setting limits at the 85th percentile speed for free-flowing conditions worked well for decades and also resulted in good levels of compliance without resort to continuous enforcement. The shift to setting limits at the median speed for free-flowing conditions has lead to a general lowering of limits (most noticeable is the shift from NSL to 50mph limits on single-carriageway roads) which are then widely ignored absent enforcement.

I couldn't agree more with this. The most baffling and frustrating change I experienced was on the A roads in Sussex, which were changed from NSL with broken white lines, where appropriate, to a 50mph limit everywhere in combination with solid white lines. Motorcyclists are condemned to either conform as with four wheeled traffic, or break the rules. It makes a mockery of the training of the IAM and the guidance in Roadcraft; indeed, it rewards complacency within the wider populous.

 

[pmcgsmurf]

Stirling council has recently put up 20mph signs on most of the side streets and some of the main roads.

When driving down these roads at 22mph on speed limiter I've had folks flashing their lights at me and overtaking me! Taxis seem to be the worse.

 

[SW18]

Stirling council has recently put up 20mph signs on most of the side streets and some of the main roads.

When driving down these roads at 22mph on speed limiter I've had folks flashing their lights at me and overtaking me! Taxis seem to be the worse.

It’s the same round here. I find 25mph (indicated) to be a sweet spot, reducing the number of drivers who get irate and overtake. I do also think that over time drivers do adjust to the new normal, we’ve had 20mph limits for 5 years now and I’m certain that more people accept it. After all, everyone ends up stopped at the next set of lights.