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Netherlands reduces speed limit to 100 km/h in daytime

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Bletchleyite

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So a genuine question here - if the speed limit was reduced from 60mph to 50mph on a single lane A road, the throughput of traffic per hour would go down I assume which might mean an increase in pollution if jams occur as a result? Would that be the case or is it a negligible impact?

Lower speeds actually reduce jams and increase throughput (though not latency) by allowing cars to travel closer together. It's the whole principle of Smart Motorways.
 
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DerekC

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So a genuine question here - if the speed limit was reduced from 60mph to 50mph on a single lane A road, the throughput of traffic per hour would go down I assume which might mean an increase in pollution if jams occur as a result? Would that be the case or is it a negligible impact?

Traffic flow is a surprisingly complicated science, but as I understand it, on a motorway (or a well designed single lane road of reasonable with no junctions and gentle curves) the optimum capacity is delivered at 50 to 55 mph. That's (as @Bletchleyite says) why smart motorways slow you down as traffic increases. So 60mph to 50mph would in theory give a capacity increase. However real single lane roads have bends, narrow sections. junctions etc etc so in reality it is unlikely to make any difference because the capacity will be way below the theoretical maximum anyway.
 

Bletchleyite

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Traffic flow is a surprisingly complicated science, but as I understand it, on a motorway (or a well designed single lane road of reasonable with no junctions and gentle curves) the optimum capacity is delivered at 50 to 55 mph. That's (as @Bletchleyite says) why smart motorways slow you down as traffic increases. So 60mph to 50mph would in theory give a capacity increase. However real single lane roads have bends, narrow sections. junctions etc etc so in reality it is unlikely to make any difference because the capacity will be way below the theoretical maximum anyway.

And you spend a fraction of the time actually at 60mph for the same reason.
 

bramling

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And you spend a fraction of the time actually at 60mph for the same reason.

I just don’t buy this. Sure many roads in the congested south-east flow slower than the speed limit, however there’s many decent-quality rural routes elsewhere in the country where it’s quite practicable to sustain 60mph for reasonably long periods - especially at outlying times of day.

Holidays in the north-east are particularly refreshing, where it’s rare *not* to have a journey relatively unhindered by others. For some reason the standard of driving in the NE seems particularly above par.
 

DerekC

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I just don’t buy this. Sure many roads in the congested south-east flow slower than the speed limit, however there’s many decent-quality rural routes elsewhere in the country where it’s quite practicable to sustain 60mph for reasonably long periods - especially at outlying times of day.

Doesn't change the fact that capacity is higher at 50 mph than 60 mph, though. Your refreshing drive on a road in the north east is by definition running at a small fraction of its capacity - otherwise I am sure you wouldn't find it refreshing!
 

bramling

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I remember it well. Even in the '70s, most cars that ordinary people owned wouldn't easily go at speeds over 70 continuously so the 50 limit was broadly kept to (certainly most would go less than 60 on open roads. I didn't live near any motorways so can't comment on what happened on them. The big differences now are that almost any car or van can happily cruise at 70 for miles and there is a sub-culture of speeding by some self-entitled drivers, (often justified by some bad science about how their car/driving style is actually less polluting and they are much more alert and less likely to be involved in incidents at illegal speeds), so any attempt to reduce actual speeds would need to be backed-up with comprehensive enforcement measures.
One good measure is that electric cars are not only zero emission at the poinnt of use, but also, when running at sustained high speeds, the reduced range will be more apparent, which might help teach those drivers to moderate their behaviour. If they think that they can avoid such limitations by sticking with polluting IC engined vehicles, the ever increasing cost penalties of such vehicles versus electric will at least give everybody else a return.

Out of curiosity, I’d be interested to see a list of which groups you regard as self-entitled or self-important, since this seems to be a theme which raises itself quite frequently with your posts. We have motorists and rail commuters (especially those who have the audacity to utilise a season ticket), which seems to cover quite a segment of the population. Add to that anyone who voted to leave the EU of course.

I trust that you don’t travel yourself, or utilise goods and services which rely on road transport for their delivery? Can’t help but recall the advocating how rail users should be grateful for a minimum standard of accommodation on a certain class of train, when we then find out that a certain person is a frequent user of declassified first-class accommodation on the said trains! ;)

More generally I can sympathise with some of the sentiments elsewhere on this thread regarding older generations. Certainly in my experience the “baby boom” types are by far the worst in that in many cases car is simply the default mode of transport for more-or-less any journey. Younger people seem far more open to being less wedded to the car.
 
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bramling

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Doesn't change the fact that capacity is higher at 50 mph than 60 mph, though. Your refreshing drive on a road in the north east is by definition running at a small fraction of its capacity - otherwise I am sure you wouldn't find it refreshing!

That’s a fair point if we’re talking about roads which are permanently running at capacity. This simply isn’t the case across the board, and those roads which run at capacity will likely have a natural decrease in flow speed anyway - especially single carriageways. The point made elsewhere about dangerous overtakes is a valid one, however IMO reducing the speed limit is not the right solution for that issue.
 

AM9

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Out of curiosity, I’d be interested to see a list of which groups you regard as self-entitled or self-important, since this seems to be a theme which raises itself quite frequently with your posts. We have motorists and rail commuters (especially those who have the audacity to utilise a season ticket), which seems to cover quite a segment of the population. Add to that anyone who voted to leave the EU of course.
There are self-entitled individuals everywhere, even some vote remain baby boomers. My references to self-entitled types are specifically about their actual behaviour or posted claims about their entitlement.

I trust that you don’t travel yourself, or utilise goods and services which rely on road transport for their delivery? Can’t help but recall the advocating how rail users should be grateful for a minimum standard of accommodation on a certain class of train, when we then find out that a certain person is a frequent user of declassified first-class accommodation on the said trains! ;)
I mostly walk to do my regular shopping, occasionally using service buses that are running anyway. I have little chance to influence how goods I buy from those that shops that I walk to get there but as I said, I do control how I take them home. Things that I buy but can't carry or take on public transport, are delivered, just like everybody elses but I don't add to the traffic by driving around just to get what I want.
I walk to the local stations and use (electric) trains that also run whether I'm on them or not. I travel in seats that my paid-for tickets entitle me to do so and are convenient for my boarding and/or alighting stations exits. I rarely add to the crush loads of peak services but accept that my much more expensive ticket only entitles me to travel, - not to a seat.

More generally I can sympathise with some of the sentiments elsewhere on this thread regarding older generations. Certainly in my experience the “baby boom” types are by far the worst in that in many cases car is simply the default mode of transport for more-or-less any journey. Younger people seem far more open to being less wedded to the car.
Many of my generation (but not all) behave with little consideration for younger ones and it is in their profligate use of energy and consequential creation of pollution that causes the biggest threat to their children and grandchildren's environment. I wish that it was not so.
 

Shaw S Hunter

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More generally I can sympathise with some of the sentiments elsewhere on this thread regarding older generations. Certainly in my experience the “baby boom” types are by far the worst in that in many cases car is simply the default mode of transport for more-or-less any journey. Younger people seem far more open to being less wedded to the car.

As a life-long voluntary non-driver in my late 50s, so definitely a boomer, I would be grateful if you would refrain from tarring such a large group of people with the same brush. Note also a contributor to this thread admitted to being a 23-year-old with little conscience about their travel mode choices. So quit with the generalisations!
 

MotCO

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I've always been confused by the assertion that reducing motorway speed limits during periods of congestion increases overall throughput. I liken it to turning on a tap; the more open the tap, the faster the flow of water. Why is it that a faster speed limit does not increase the flow of traffic? Is it because water, unlike traffic, is a constant flow with no human reaction to distance betwen vehicles?
 

bramling

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I've always been confused by the assertion that reducing motorway speed limits during periods of congestion increases overall throughput. I liken it to turning on a tap; the more open the tap, the faster the flow of water. Why is it that a faster speed limit does not increase the flow of traffic? Is it because water, unlike traffic, is a constant flow with no human reaction to distance betwen vehicles?

Must motorway congestion (especially that causes simply by weight of traffic, as opposed to that caused by obstructions like lane closures) is caused by the chain-reaction effect of people seeing brake lights in front of them and then braking that little bit more, until eventually speed reduces to zero.

The idea of varying the speed limits is that people slow in advance by easing off their accelerator pedal rather than needing to use the brake pedal, which reduces the bunching. Unfortunately this is anathema to many people, hence congestion still occurs.

It's also supposed to reduce the amount of lane changing - which contributes to congestion when someone misjudges and cuts in front of a faster vehicle which causes brake lights to illuminate. Again, unfortunately it only works if people play ball, and some people seem to feel the need to frequently change lanes for no real reason, like children having sweets dangled in front of their eyes.
 

edwin_m

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I've always been confused by the assertion that reducing motorway speed limits during periods of congestion increases overall throughput. I liken it to turning on a tap; the more open the tap, the faster the flow of water. Why is it that a faster speed limit does not increase the flow of traffic? Is it because water, unlike traffic, is a constant flow with no human reaction to distance betwen vehicles?
Someone pointed out further up that at a higher speed there should be longer gaps between each vehicle. The gap should be at least braking distance, which increases as the square of speed, whereas (if the gap didn't increase) the number of vehicles passing would only increase linearly with speed. So at higher speeds capacity decreases, and the maximum capacity on a motorway-type road is at around 50mph.

Of course what really happens is that people drive at less than braking distance from the car in front, especially when the road is busy. That makes it more likely that people will have to brake suddenly, causing the effect mentioned by bramling above, not to mention the increased risk of accidents.
 

Bald Rick

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Must motorway congestion (especially that causes simply by weight of traffic, as opposed to that caused by obstructions like lane closures) is caused by the chain-reaction effect of people seeing brake lights in front of them and then braking that little bit more, until eventually speed reduces to zero.

The idea of varying the speed limits is that people slow in advance by easing off their accelerator pedal rather than needing to use the brake pedal, which reduces the bunching. Unfortunately this is anathema to many people, hence congestion still occurs.

It's also supposed to reduce the amount of lane changing - which contributes to congestion when someone misjudges and cuts in front of a faster vehicle which causes brake lights to illuminate. Again, unfortunately it only works if people play ball, and some people seem to feel the need to frequently change lanes for no real reason, like children having sweets dangled in front of their eyes.

It’s not congestion, per se, that is the issue. The output is quantity of traffic, journey times, and accident rates. The Highways agency (as the were then) did some analysis after the first (experimental) section of Smart Mororway was introduced on the M42 Between Solihull and the M6. I cant find the report now, but it increased capacity by much more than expected, improved journey times much more than expected and reduced accidents. There are still jams of course, but it is much better than it would have been without the ‘smart’ system.
 

notadriver

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I don't know what motorways you've been using, but unless it's the M25 or M6 through Birmingham, it's relativley easy to hit 70mph (or even 80-90mph if you're brave/stupid enough)

Do drivers go faster at night ? I’m pretty sure 80-90 mph is the norm over the M2 Medway motorway bridge which is 4 lanes across but in the late evenings I’ve been doing 135-140 mph and had trouble catching up certain cars.
 

edwin_m

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Do drivers go faster at night ? I’m pretty sure 80-90 mph is the norm over the M2 Medway motorway bridge which is 4 lanes across but in the late evenings I’ve been doing 135-140 mph and had trouble catching up certain cars.
I hope you've been doing that speed in a train on the HS1 bridge alongside!

Maybe just a matter of the road being quieter so the boy racers come out to play?
 

AM9

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I hope you've been doing that speed in a train on the HS1 bridge alongside!

Maybe just a matter of the road being quieter so the boy racers come out to play?
There's a perception that speed detectionn cameras don't (or won't) work in darkness. I think some of the newer types do so at some point, there will be a sudden increase in prosecutions.
 

Bald Rick

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There's a perception that speed detectionn cameras don't (or won't) work in darkness. I think some of the newer types do so at some point, there will be a sudden increase in prosecutions.

Oh they definitely work at night. Hence the double flash on the ‘spot’ cameras. Not so sure about average speed cameras, but I certainly wouldn’t risk it.
 

mmh

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Many drivers have no actual reason to drive

This is never true. Just wanting to do something for the sake of itself is a reason.

Just as some people take rail journeys for their own right with no other reason than pleasure, so do some people drive for pleasure.

I don't want to live in a world so joyless that someone is pilloried for a Sunday afternoon drive, or on the other hand an All Line Rover holiday.

Large parts of the economy, in this country as well as others, would die without journeys for enjoyment.
 

Busaholic

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There's a perception that speed detectionn cameras don't (or won't) work in darkness. I think some of the newer types do so at some point, there will be a sudden increase in prosecutions.
Well, my first time of being 'caught' by a fixed speed camera, twenty years ago, was at 1 a.m. on an unlit road, at a time when the cameras didn't have to signal their presence with yellow paint! Only going at 5 mph over the allowed 60 on a dead straight road too.
 

underbank

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The idea of varying the speed limits is that people slow in advance by easing off their accelerator pedal rather than needing to use the brake pedal, which reduces the bunching. Unfortunately this is anathema to many people, hence congestion still occurs.

But if there are real reasons for slow traffic, i.e. badly designed junctions and entry/exit sliproads causing bottlenecks, they're as much use as a chocolate fireguard. Take the M60 West of Manchester. The variable speed limits are a complete waste of time because stationery or 5/10 mph traffic is a daily fact of life. That's nothing to do with late braking, driving too close, etc - it's simply poorly laid out junctions and volume of traffic. Even if all traffic approached it at 5mph, it would still be stop/stop & clogged up.
 

Bletchleyite

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But if there are real reasons for slow traffic, i.e. badly designed junctions and entry/exit sliproads causing bottlenecks, they're as much use as a chocolate fireguard. Take the M60 West of Manchester. The variable speed limits are a complete waste of time because stationery or 5/10 mph traffic is a daily fact of life. That's nothing to do with late braking, driving too close, etc - it's simply poorly laid out junctions and volume of traffic. Even if all traffic approached it at 5mph, it would still be stop/stop & clogged up.

This may be true, but (a) you need an exception to prove the rule, and (b) there being some locations where smart motorways won't work is not a reason not to put them elsewhere where they demonstrably do (though I do agree that part time hard shoulder running is a rubbish idea).
 

reddragon

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I used to drive a 2001 diesel, it always did 55 mpg. I did once drive like grandma back from Scotland & got it up to 65 mpg just once. No clouds of smoke & always clean (ish)

I then got a 2008 model. If I drove it gently it only did 35 mpg, if I trashed it I got 50 mpg! Something to do with cleaner engines! Always had clouds of smoke out the tail pipe but passed its MOT!! Something stinks here?

Cars delivered up to August 2019 are as filthy as hell, many up to 20x advertised pollution rates - its wasn't only VW that were dodgy, they all were. Only cars made since September are actually as clean as advertised due to very strict testing. Thats why there are so many nearly new zero miles cars for sale lately at half price!

I now drive an EV, so I asked the Welsh highways why I had to slow down to 50mph on the M4 to lower pollution when they brought that in a few months back. I never got a sensible answer!
 

Bletchleyite

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I now drive an EV, so I asked the Welsh highways why I had to slow down to 50mph on the M4 to lower pollution when they brought that in a few months back. I never got a sensible answer!

It would probably cause unnecessary confusion for one class of passenger car (as distinct from a lorry with a limiter) to have a different limit, to be honest.
 

reddragon

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It would probably cause unnecessary confusion for one class of passenger car (as distinct from a lorry with a limiter) to have a different limit, to be honest.

Quite apart from the fact TfL achieve that for the ULEZ, TfWales were unable even to come up with an answer that credible!
 

Bald Rick

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I used to drive a 2001 diesel, it always did 55 mpg. I did once drive like grandma back from Scotland & got it up to 65 mpg just once. No clouds of smoke & always clean (ish)

Anecdote being the worst form of evidence...

I had a 2005 Golf 2.0 GTD which would average mid to high 40s mpg on our typical usage, and on a 100mile + motorway run would average 65mpg or so if driven ‘carefully’.

It was replaced with a 2010 Golf 2.0 GTD which averages high 40s to low 50s on our typical average usage, and on a 100mile + motorway run will average 70mpg if driven carefully. I once got it to 78mpg on a 125mile journey (door to door), which with 4 of us on board would have been 24g CO2/ person km if I have done my sums right.

Sperately, I’d like to see evidence of why ‘nearly new’ cars are being sold for ‘half price’. The manufacturers testing regime may have changed, but as far as the MoT testing, and all congestion / ULEZ type charging is concerned, it doesn’t make any difference. So what would they being sold cheap?
 

reddragon

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Sperately, I’d like to see evidence of why ‘nearly new’ cars are being sold for ‘half price’. The manufacturers testing regime may have changed, but as far as the MoT testing, and all congestion / ULEZ type charging is concerned, it doesn’t make any difference. So what would they being sold cheap?

Because any non-compliant car could not be sold after 31/8/2019. They had to pre-register them, store them and were time limited by the manufacturers in the time to clear the stock
 

Bald Rick

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Because any non-compliant car could not be sold after 31/8/2019. They had to pre-register them, store them and were time limited by the manufacturers in the time to clear the stock

Really? Why would the manufactures want to clear their stock and lose money? I can’t find any evidence of nearly New cars at delivery mileage being sold at half price.
 
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