M1 Speed Limit In Sheffield

[Arnold_Lane 0]

12 minutes ago, busdriver1 said:

Oh so it does not fit your agenda then and you still haven't answered my question  - wonder why 

No I dont, I know exactly why

The reply of a true scholar in his field.

[butlers 259]

Even though cars are slippier than in days of old ,still think air resistance is expotenial .

Everything I can find is from 55 mph upwards it's more noticable.

 

 

[DT Ralge 10]

Copying from an earlier post against which I can’t argue (laws of physics, I’m told):

 

”At both those speeds almost all the effort is in overcoming air resistance, which is proportional to velocity squared. So travelling at 70 requires about 36% more effort than travelling at 60 does. It would be a very strange engine that could produce 36% more power output for a marginal increase in fuel consumption.”

 

No-one argued against this point when it was made.   Can anyone sink the basis of this argument, whether or not it takes a degree in Physics. 

Edited September 16, 2020 by DT Ralge

[butlers 259]

That's much better phrasing than I managed!

[altus 537]

19 minutes ago, DT Ralge said:

Copying from an earlier post against which I can’t argue (laws of physics, I’m told):

 

”At both those speeds almost all the effort is in overcoming air resistance, which is proportional to velocity squared. So travelling at 70 requires about 36% more effort than travelling at 60 does. It would be a very strange engine that could produce 36% more power output for a marginal increase in fuel consumption.”

 

No-one argued against this point when it was made.   Can anyone sink the basis of this argument, whether or not it takes a degree in Physics. 

I'm not going to sink the point, as I was the one who made it, but I will put it in a bit of context.

 

I was only responding to the 'air resistance is negligible' argument. If you factor in the reduced travel time of 70 vs 60, the difference in total emissions would be about 17%.

[Rockers rule 673]

3 hours ago, DT Ralge said:

 
 

Drivers need to take ownership and responsibility and not be quite so reliant on all sorts of technology ...  that way they may just finish up as better, more astute risk managers. 
Pigs might fly, though. 

Talking of Reliant's why didn't despite the Robin being more aerodynamic handle as good as the brick sided Regal?

 

Lot of talk about wind rather than talk about solving the problem of congestion on our motorways.

Up the speed limit, lets get to where we're going and spend less time in anyone area  =  less pollution.

 

Less hot air more forward motion. 

 

 

 

 

 

[butlers 259]

Is that a little like driving faster to get to petrol station when the guage is low,logic

[Rockers rule 673]

NO 

Edited September 16, 2020 by Rockers rule
additional info

[Arnold_Lane 0]

44 minutes ago, Rockers rule said:

NO 

I don't know the distance between the junctions.  Let's call it 10 miles.

 

It takes 86 seconds longer to travel that distance at 60 mph than 70 mph.

 

What figures do you have for emissions per second at 60 mph and 70 mph?

[dave_the_m 61]

2 hours ago, Rockers rule said:

Up the speed limit, lets get to where we're going and spend less time in anyone area  =  less pollution.

 

 

It really doesn't work like that. A simplified example: assume (on average) that cars are more fuel efficient going at 60mph rather than 70mph. Assume also (as a gross simplification) that the amount of pollutants produced by a car is directly proportional to the amount of petrol consumed. Then a car travelling between any two points A and B at 60mph will consume less petrol, and thus emit less pollutants along that stretch between A and B, than one going at 70mph - even though the faster car spends less actual time between A and B.

[DT Ralge 10]

55 minutes ago, dave_the_m said:

It really doesn't work like that. A simplified example: assume (on average) that cars are more fuel efficient going at 60mph rather than 70mph. Assume also (as a gross simplification) that the amount of pollutants produced by a car is directly proportional to the amount of petrol consumed. Then a car travelling between any two points A and B at 60mph will consume less petrol, and thus emit less pollutants along that stretch between A and B, than one going at 70mph - even though the faster car spends less actual time between A and B.

Wot he says ...

[DT Ralge 10]

3 hours ago, Rockers rule said:

Talking of Reliant's why didn't despite the Robin being more aerodynamic handle as good as the brick sided Regal?

 

Lot of talk about wind rather than talk about solving the problem of congestion on our motorways.

Up the speed limit, lets get to where we're going and spend less time in anyone area  =  less pollution.

 

Less hot air more forward motion. 

 

 

 

 

 

 I'm repeating myself - a steadier queue of traffic all moving at around the same speed, 60, with little motivation for drivers to change lanes to overtake and no point in acceleration followed by braking.  Brake lights, in themselves, cause others to brake (the ripple effect) and generates a pattern of stop/start traffic and unnecessary tailbacks.

A lowered speed limit is targeted at controlling drivers' expectations and there are benefits to be had from this steadier, one speed, flowing queue, including fewer jams, lower emissions and pollution.

Edited September 16, 2020 by DT Ralge