Well, well, well. Who'd have thought it? Increased speed limits produce tangible benefits

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st13phil

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So, contrary to the shrill cries of Brake and their ill-informed buddies, the increase in HGV speed limits to 50mph and 60mph on single carriageway roads and dual carriageways respectively that came into force in 2015 "has saved businesses millions of pounds a year and could have helped improve road safety".

DfT news story here.

According to a report commissioned by the DfT, allowing heavy goods vehicles over 7.5 tonnes to travel 10mph faster, bringing them closer to the speed of other traffic, has contributed to an increase of 1.5mph in average speeds on single carriageway roads. An increase of just 1mph would free up 650,000 driver hours and save hauliers more than £10 million a year. The report also shows there is a possible “statistically significant” improvement to road safety on study roads.

So no carnage then :rolleyes:
 
So, contrary to the shrill cries of Brake and their ill-informed buddies, the increase in HGV speed limits to 50mph and 60mph on single carriageway roads and dual carriageways respectively that came into force in 2015 "has saved businesses millions of pounds a year and could have helped improve road safety".

DfT news story here.

According to a report commissioned by the DfT, allowing heavy goods vehicles over 7.5 tonnes to travel 10mph faster, bringing them closer to the speed of other traffic, has contributed to an increase of 1.5mph in average speeds on single carriageway roads. An increase of just 1mph would free up 650,000 driver hours and save hauliers more than £10 million a year. The report also shows there is a possible “statistically significant” improvement to road safety on study roads.

So no carnage then :rolleyes:

possible “statistically significant” improvement to road safety on study roads. AKA lying with statistics to prove a point:).....

Reading your post it seems only the hauliers have really benefited......and I doubt any benefits will find their way back to the consumer.:oops:
 
Maybe the reference to average speeds includes other traffic?

I always wonder about statements like "possible “statistically significant”".

It reminded me of the news headline last week, about the number of people that watched women's WC soccer vs the WC cricket (IIRC in the order of 10 to 1) - they conveniently forgot to mention that soccer was on a free to view, cricket was on a pay channel and IIRC the soccer was a knockout game which the cricket was not.

When I started work (1971, working with stats was part of my job) "How to Lie with Statistics" - written by Darrell Huff in 1954, made interesting reading (an 18 year old book (at the time) and is still on sale.
 
A few comments after a quick glance over the actual report produced by the American multinational engineering consultancy firm AECOM
motto Imagine it-Delivered!
Second report on the increased speed limit for heavy goods vehicles.
Based on the "do no harm" aspect of the changes I was drawn to this paragraph
Summary of Safety Impacts
This section has considered the impact of the national HGV speed limit increase on
personal injury collisions on all study roads and on single carriageway roads. This
analysis was based on the ex-post data available to date. As collisions are stochastic
(occurring randomly) events whose frequency is subject to fluctuations over time,
statistical models were fitted to the collision data to understand how the ex-post
collisions differ to what might have been expected to occur without the policy change.
It was shown that across all study roads (single and dual) there is evidence of a
statistically significant reduction in collisions involving at least one HGV (the collisions
that are the focus of this study) since the HGV speed limit change.
However, it also
demonstrated that this finding is very sensitive, as when the 2016 Q4 data was
removed from the model, the result was no longer significant. The observed 2016 Q4
data was showing unusual behaviour compared to previous seasonality trends, and so
further evidence from the Year 3 analysis is required to provide confidence on the
outcome.

This section also considered the change in collisions involving at least one HGV on
single carriageway roads since the HGV speed limit change. In summary, the recorded
data suggested that there has not been any statistically significant change in the
number of collisions involving at least one HGV on single carriageway roads since the
HGV speed limit change
 
HGVs and buses seem to go way too quick on urban roads.
 
I note that pollution doesn’t get a mention: was measurement of net pollution change not included in the study? I would think that increases could be material given the additional energy required to make large vehicles travel faster. I’ve no strong opinion, just interested...
 
But when HGV's hold up other traffic that can increase pollution just as all the green cyclists are increasing the pollution produced by the traffic that has to overtake them.
 
But when HGV's hold up other traffic that can increase pollution just as all the green cyclists are increasing the pollution produced by the traffic that has to overtake them.
Yes, all fair points and even more reason why it would be good if pollution changes were assessed in the study.
 
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Yes, all fair points and even more reason why it would be good if pollution changes were assessed in the study.
From the link in my post, click through to the report. There’s a whole section on environmental impacts.
 
Environmental impacts were dealt with here.
Environment
Figure 4.1
presents the ex-ante causal pathway for the environmental impacts of the
speed limit change, focusing on the level of emissions. The ex-ante impact
assessment of the speed limit change predicted a reduction in NOx emissions on
single carriageway roads, as a consequence of HGVs travelling at slightly more
efficient engine speeds at the higher end of possible increases in HGV speed assumed
in the test (an increase of approximately 4 mph to 49 mph– this increase was taken
from the higher end of speed increases tested within the DfT impact assessment for
single carriageways). The evidence from the Year 2 evaluation has identified an
average speed of HGVs of 45.6 mph on single carriageways,
although as noted in
Section 2 this was an increase on the pre-2015 figure of 44.1 mph.
For PM 10 12 emissions, although some vehicle types were forecast in the impact
assessment to operate more efficiently at increased speeds, other types would be
above their most efficient speed if average speeds increased to approximately 49 mph
as forecast. The ex-ante analysis forecast an overall increase in PM10 emissions. No
firm conclusions could be drawn on PM 10 emissions from the 2016 interim analysis and
this issue will be considered further in the Year 3 evaluation.

for " ex-ante " causal read "non" causal
explained here
https://www.quora.com/What-are-causal-and-non-causal-system
quote:-
Since non-causal system contains future samples; a non-causal system is practically not realizable. That means in practical cases it is not possible to implement a non-causal system. In other words these are predictions not data.

One possible comment would be that environmental projections based on single carriageway measurements made at lower speeds could possibly minimise the effect of increased aerodynamic drag at higher speeds which might well negate any increased engine efficiency postulated.
The more I read the more it presents a picture of a study designed to reach a certain conclusion by selective presentation of evidence.
 
"if you torture the data long enough, it will confess to anything"

From Darrell Huff's book How to Lie With Statistics(1954).

Sent from my awesome Samsung Galaxy Note 9
 
I always wonder about statements like "possible “statistically significant”".

It reminded me of the news headline last week, about the number of people that watched women's WC soccer vs the WC cricket (IIRC in the order of 10 to 1) - they conveniently forgot to mention that soccer was on a free to view, cricket was on a pay channel and IIRC the soccer was a knockout game which the cricket was not.

When I started work (1971, working with stats was part of my job) "How to Lie with Statistics" - written by Darrell Huff in 1954, made interesting reading (an 18 year old book (at the time) and is still on sale.
While I’m not a fan of either, it has to be remembered that cricket is a predominantly English game , with relatively little following elsewhere , while football has a huge global following.
 
A few comments after a quick glance over the actual report produced by the American multinational engineering consultancy firm AECOM
motto Imagine it-Delivered!
Second report on the increased speed limit for heavy goods vehicles.
Based on the "do no harm" aspect of the changes I was drawn to this paragraph
Summary of Safety Impacts
This section has considered the impact of the national HGV speed limit increase on
personal injury collisions on all study roads and on single carriageway roads. This
analysis was based on the ex-post data available to date. As collisions are stochastic
(occurring randomly) events whose frequency is subject to fluctuations over time,
statistical models were fitted to the collision data to understand how the ex-post
collisions differ to what might have been expected to occur without the policy change.
It was shown that across all study roads (single and dual) there is evidence of a
statistically significant reduction in collisions involving at least one HGV (the collisions
that are the focus of this study) since the HGV speed limit change.
However, it also
demonstrated that this finding is very sensitive, as when the 2016 Q4 data was
removed from the model, the result was no longer significant. The observed 2016 Q4
data was showing unusual behaviour compared to previous seasonality trends, and so
further evidence from the Year 3 analysis is required to provide confidence on the
outcome.

This section also considered the change in collisions involving at least one HGV on
single carriageway roads since the HGV speed limit change. In summary, the recorded
data suggested that there has not been any statistically significant change in the
number of collisions involving at least one HGV on single carriageway roads since the
HGV speed limit change
A lot depends on how you define ‘collisions involving at least one HGV’ : if someone overtakes an HGV and hits another vehicle , but not the HGV , was the HGV ‘involved’ ?

Or like the crash outside my house last year , car turning off into unsighted side road on left , confronted by HGV coming down the narrow road and stops dead in the mouth of the junction without hitting HGV , I manage to stop without hitting him , and the car behind stops without hitting me , but is shunted from behind and the following 4 or 5 cars end up in a pile up .
Was that HGV , arguably too big for that road because it took up most of the width , involved in the crash ? It was certainly a factor .
 
While I’m not a fan of either, it has to be remembered that cricket is a predominantly English game , with relatively little following elsewhere , while football has a huge global following.

Big in India, Pakistan, West Indies, Australia .....
 
I have a degree of sympathy for the American company trying to make sense of a complex problem with a limited data set. To facilitate this they appear to have turned to modelling to draw some of their conclusions. Where they are open to criticism is in their selection of previous data to use in their model. By appearing to randomly change the scope of same such as the vehicles/roads/seasons included/excluded-- its as if they decided what the results were and then by careful selection of data input drew the desired conclusion or at minimum presented a rather more optimistic picture than the limited data might suggest.
The conclusion that average vehicle speeds increased slightly with a raising of the speed limits on single and dual carriageways is clear enough---indeed might be characterised as self evident--- the safety and environmental data less so. ;)
 
Big in India, Pakistan, West Indies, Australia .....
Yep , the half dozen ex English colonies who participate , compared to almost every country in the world which plays and follows football .
 
While I’m not a fan of either, it has to be remembered that cricket is a predominantly English game , with relatively little following elsewhere , while football has a huge global following.
I think they were talking about British viewers..
 
From the link in my post, click through to the report. There’s a whole section on environmental impacts.

Environmental impacts were dealt with here.
Environment
Figure 4.1
presents the ex-ante causal pathway for the environmental impacts of the
speed limit change, focusing on the level of emissions. The ex-ante impact
assessment of the speed limit change predicted a reduction in NOx emissions on
single carriageway roads, as a consequence of HGVs travelling at slightly more
efficient engine speeds at the higher end of possible increases in HGV speed assumed
in the test (an increase of approximately 4 mph to 49 mph– this increase was taken
from the higher end of speed increases tested within the DfT impact assessment for
single carriageways). The evidence from the Year 2 evaluation has identified an
average speed of HGVs of 45.6 mph on single carriageways,
although as noted in
Section 2 this was an increase on the pre-2015 figure of 44.1 mph.
For PM 10 12 emissions, although some vehicle types were forecast in the impact
assessment to operate more efficiently at increased speeds, other types would be
above their most efficient speed if average speeds increased to approximately 49 mph
as forecast. The ex-ante analysis forecast an overall increase in PM10 emissions. No
firm conclusions could be drawn on PM 10 emissions from the 2016 interim analysis and
this issue will be considered further in the Year 3 evaluation.

for " ex-ante " causal read "non" causal
explained here
https://www.quora.com/What-are-causal-and-non-causal-system
quote:-
Since non-causal system contains future samples; a non-causal system is practically not realizable. That means in practical cases it is not possible to implement a non-causal system. In other words these are predictions not data.

One possible comment would be that environmental projections based on single carriageway measurements made at lower speeds could possibly minimise the effect of increased aerodynamic drag at higher speeds which might well negate any increased engine efficiency postulated.
The more I read the more it presents a picture of a study designed to reach a certain conclusion by selective presentation of evidence.

I have a degree of sympathy for the American company trying to make sense of a complex problem with a limited data set. To facilitate this they appear to have turned to modelling to draw some of their conclusions. Where they are open to criticism is in their selection of previous data to use in their model. By appearing to randomly change the scope of same such as the vehicles/roads/seasons included/excluded-- its as if they decided what the results were and then by careful selection of data input drew the desired conclusion or at minimum presented a rather more optimistic picture than the limited data might suggest.
The conclusion that average vehicle speeds increased slightly with a raising of the speed limits on single and dual carriageways is clear enough---indeed might be characterised as self evident--- the safety and environmental data less so. ;)

Thanks - I enjoyed a read of the report and agree that there may have been a touch of confirmation bias at work.

I guess a conundrum for a consultancy is do they act objectively or do they take their steer from the client (and paymaster) to ensure they continue to get future work! This is of course not a problem confined to the scientific community but seen widely e.g. Carillion and it’s auditor KPMG (there seem to be examples for every large audit firm lately).
 

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