New Speed limit on Motorways (1 Viewer)

[wizzer59]

God help us. I'm driving up to a 100 miles a day in my works van, and try to stick to sixty to conserve fuel and be safe, but to try and overtake on motorways is bad enough now with people tailgating at 80 or more so what is it going to be like at 90 or moreoh:. just wish we would all leave more space between us:thumb:

I'm afraid I'm very much against this, in a time when we should all be conserving fuel and the planet.

And I'm not whiter than white Ive done all of these things much to my regret:Blush:

 

[JJ]

for those that can't be bothered to click the link,,


Thanks Paul.... now I can enjoy your post whereas had it been a link I wouldn't have.... :thumb:

JJ :Cool:

 

[scotjimland]

Something I haven't seem mentioned here or on the media is road capacity ...

now, I may be wrong here, but if you raise speeds don't you lower capacity... ?

this is why (so I have been told) that there are sections of the M25 with a 50mph limit.. not for safety but to increase capacity ...

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[JJ]

Just as I thought... if I don't die on the roads here in Portugal I will live until I am 100!!!

It is often madness out there....:Sad:

JJ :Cool:

 

[GJH]

Something I haven't seem mentioned here or on the media is road capacity ...

now, I may be wrong here, but if you raise speeds don't you lower capacity... ?

this is why (so I have been told) that there are sections of the M25 with a 50mph limit.. not for safety but to increase capacity ...

The use of variable speed limits on some motorways was mentioned during a discussion of this subject on local radio yesterday and the point was made that lower speeds can, sometimes, mean faster journeys because they improve the overall flow of traffic.

AFAIK the consultation on raising the upper limit would not mean doing away with variable limits.

 

[chrisgreen]

lets do away with motorway speed limit's:thumb:
iv driven on the autoban in germany and thought what a great idea,no limits:thumb:
mind you i was limited by the transit twin wheeler i was driveing at about 75mph flatoutoh:

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[scotjimland]

AFAIK the consultation on raising the upper limit would not mean doing away with variable limits.

Yes, I appreciate that but would raising from 70 to 80 not also affect the overall capacity?

 

[callumwa]

Yes, I appreciate that but would raising from 70 to 80 not also affect the overall capacity?

Only if you are assuming the road is already operating at 100% capacity......

 

[GJH]

Yes, I appreciate that but would raising from 70 to 80 not also affect the overall capacity?

Oh 'eck, I feel an attack of logic coming on

Depends what we mean by "overall capacity".

Think of a motorway as being like a water pipe. If you open a tap wider then:
a) to fill any container will take less time because the water is flowing faster
b) in a given amount of time it is possible to run more water though the length of pipe.
Thus, whilst the physical capacity (pipe diameter/road width) is fixed the throughput capacity is increased at the higher rate of flow (= speed).

The difference, though, is that all the water travels at the same speed but vehicles on a road travel at different speeds, the result being that slower vehicles sometimes hinder faster vehicles and the stop/start (domino?) effect slows down overall flow rate. If the speed of slower vehicles stays the same and that of faster vehicles increases than the potential for hindrance, and thus more stop/start, would increase. On that basis throughput capacity would be reduced.

The use of variable speed limits improves the overall flow of traffic (throughput capacity) because it reduces the speed difference between slower and faster vehicles and, by doing so, the stop/start rate.

Does that make sense?

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[scotjimland]

Only if you are assuming the road is already operating at 100% capacity......

yes, that's true.. but how many are not only at, but over capacity already.

and if not already at capacity, raising the limit will reduce the time before it is..

 

[callumwa]

Oh 'eck, I feel an attack of logic coming on

Depends what we mean by "overall capacity".

Think of a motorway as being like a water pipe. If you open a tap wider then:
a) to fill any container will take less time because the water is flowing faster
b) in a given amount of time it is possible to run more water though the length of pipe.
Thus, whilst the physical capacity (pipe diameter/road width) is fixed the throughput capacity is increased at the higher rate of flow (= speed).

The difference, though, is that all the water travels at the same speed but vehicles on a road travel at different speeds, the result being that slower vehicles sometimes hinder faster vehicles and the stop/start (domino?) effect slows down overall flow rate. If the speed of slower vehicles stays the same and that of faster vehicles increases than the potential for hindrance, and thus more stop/start, would increase. On that basis throughput capacity would be reduced.

The use of variable speed limits improves the overall flow of traffic (throughput capacity) because it reduces the speed difference between slower and faster vehicles and, by doing so, the stop/start rate.

Does that make sense?

Does to me.......:thumb:

 

[scotjimland]

Oh 'eck, I feel an attack of logic coming on

Depends what we mean by "overall capacity".

Think of a motorway as being like a water pipe. If you open a tap wider then:
a) to fill any container will take less time because the water is flowing faster
b) in a given amount of time it is possible to run more water though the length of pipe.
Thus, whilst the physical capacity (pipe diameter/road width) is fixed the throughput capacity is increased at the higher rate of flow (= speed).

The difference, though, is that all the water travels at the same speed but vehicles on a road travel at different speeds, the result being that slower vehicles sometimes hinder faster vehicles and the stop/start (domino?) effect slows down overall flow rate. If the speed of slower vehicles stays the same and that of faster vehicles increases than the potential for hindrance, and thus more stop/start, would increase. On that basis throughput capacity would be reduced.

The use of variable speed limits improves the overall flow of traffic (throughput capacity) because it reduces the speed difference between slower and faster vehicles and, by doing so, the stop/start rate.

Does that make sense?

I'm an electrician, not a plumber ... how can I understand that ..oh:

could you do that again using ohms law... Amps,Volts and Resistance ?

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[GJH]

I'm an electrician, not a plumber ... how can I understand that ..oh:

could you do that again using ohms law... Amps,Volts and Resistance ?

No - cos I only does computering

 

[johnp10]

Oh 'eck, I feel an attack of logic coming on

Depends what we mean by "overall capacity".

Think of a motorway as being like a water pipe. If you open a tap wider then:
a) to fill any container will take less time because the water is flowing faster
b) in a given amount of time it is possible to run more water though the length of pipe.
Thus, whilst the physical capacity (pipe diameter/road width) is fixed the throughput capacity is increased at the higher rate of flow (= speed).

The difference, though, is that all the water travels at the same speed but vehicles on a road travel at different speeds, the result being that slower vehicles sometimes hinder faster vehicles and the stop/start (domino?) effect slows down overall flow rate. If the speed of slower vehicles stays the same and that of faster vehicles increases than the potential for hindrance, and thus more stop/start, would increase. On that basis throughput capacity would be reduced.

The use of variable speed limits improves the overall flow of traffic (throughput capacity) because it reduces the speed difference between slower and faster vehicles and, by doing so, the stop/start rate.

Does that make sense?

Yes, it does.

I'm an electrician, not a plumber ... how can I understand that ..oh:

could you do that again using ohms law... Amps,Volts and Resistance ?

Increase the Amps (speed), Traffic volume (Volts) remains constant, = greater (Ohms) resistance to flow of traffic.....
Can actually slow down the flow.

(Tongue in cheek like yours, Jim.)

Not a sparks, so will happily be corrected if the analogy is incorrect.

 

[scotjimland]

The size of the road = the size of the cable .. ie bigger road can carry more traffic.. likewise the greater the cable size the bigger the current that can flow ..

So the Current or Volume of traffic = Amps

The speed of the current flow depends on the volts .. so voltage represents the MPH

So to increase volume you increase Voltage, which will increase the flow in Amps (number of vehicles) .. but the cable has a maximum safe current,( as does a road) exceed this and it heats up which increases resistance, further reducing the flow, (traffic crawling) .. if you continue to increase the voltage the cable will eventually get so hot it melts the insulation and eventually the copper ... major M Way pile up ..

all good fun ..

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[johnp10]

The size of the road = the size of the cable .. ie bigger road can carry more traffic.. likewise the greater the cable size the bigger the current that can flow ..

So the Current or Volume of traffic = Amps

The speed of the current flow depends on the volts .. so voltage represents the MPH

So to increase volume you increase Voltage, which will increase the flow in Amps (number of vehicles) .. but the cable has a maximum safe current,( as does a road) exceed this and it heats up which increases resistance, further reducing the flow, (traffic crawling) .. if you continue to increase the voltage the cable will eventually get so hot it melts the insulation and eventually the copper ... major M Way pile up ..

all good fun ..

Well bugger!
Does this mean I'm right, Jim?

 

[scotjimland]

Well bugger!
Does this mean I'm right, Jim?

nope... just as daft as me

 

[johnp10]

nope... just as daft as me

Can live with daft.

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