Is it time to increase the speed limit from 70mph to 80mph?

MinuteNoodles

unforeseen said:

Unless you know EXACTLY what the error is on your speedo then you will stick to an indicated 56 to ensure that the taco never records >56

Tachos are calibrated to +/-2.5% accuracy, and like car speedos are not allowed to under-read so you can never be doing a higher speed than the indicated speed unless you've altered something such as putting on larger wheels or there's a fault. A tacho has to have a 2 yearly calibration inspection and a calibration certificate attached to it or the vehicle.

MinuteNoodles

oldagetraveller1 said:

[DELETED USER] said:

The difference in energy consumption between 70 mph and 80 mph is huge. Upping the limit will just make more pollution.

And I wonder what impact that would have on the range of an EV too? Which in turn would increase the pollution from a power station because a recharge is required more often! Added to a reduction in the useful life of the batteries.

I know the answer to this. Long version short is that wind resistance vs speed increases as a function of the square. If you double your speed the wind resistance increases fourfold, triple it it goes up ninefold. Rolling resistance remains a constant. From a US Department of Energy study for petrol engined vehicles it found that once over the optimal speed of 55-60MPH as advertised by the manufacturer the results were;

    - 3% less efficient at 60 mph
    - 8% less efficient at 65 mph
    - 17% less efficient at 70 mph
    - 23% less efficient at 75 mph
    - 28% less efficient at 80 mph

Given that the majority of the reason for that lower efficiency is the increase in wind resistance you could expect a similar thing to happen with an EV.

jimbo6977

Given that France is debating lowering its motorway limit from 130 to 110 (roughly 80 to 70), in order to meet environmental targets, I think it's unlikely the UK will go the other way, given that we have similar targets to meet. 

Jack_Cork

AdrianC said:

Ganga said:

AdrianC said:

fred246 said:

Stop HGVs overtaking. That's what they do in Germany.

Have you ever been to Germany?

BTW, they don't. Not as a blanket. There are some stretches, almost all two-lane, where there's localised bans. As there are on UK motorways...

Are HGV,s not allowed in the second lane of a two lane motorway?

In certain places. As in Germany.
https://goo.gl/maps/tKHw5XBJKBxDqeAS7 for one.
18 month trial became permanent in 2009.
https://www.commercialmotor.com/news/hgv-m-overtaking-ban-becomes-permanent

I travel that stretch of the M42 most weeks. They are much, much better at sticking at the rules in Germany than the UK. 

sk2402005

With the general standard of driving that i see, then no 70 is plenty enough.

the increase of 10mph, even if you managed that across the entire country (875 miles apparently) you would save an entire hour, hardly worth it...

I actually think with the push towards being greener, they should actually drop it to 60, it will also be safer.

Jackmydad

sk2402005 said:

With the general standard of driving that i see, then no 70 is plenty enough.

the increase of 10mph, even if you managed that across the entire country (875 miles apparently) you would save an entire hour, hardly worth it...

I actually think with the push towards being greener, they should actually drop it to 60, it will also be safer.

Exactly, they might have made cars "better" in the time the limit's been in force, but they sure as heck ain't made drivers any better. Add that to the fact that the "better" cars make mediocre drivers feel as if they're good drivers, with ever more cosseting to make them feel safe, and we don't need drivers going any faster.
Also I wonder about maintenance. A yearly MOT is hardly "regular maintenance", it's not intended to be. But that, and an annual oil change, is about all some cars will get until something is obviously wrong.. If they're lucky that is.
So we're looking at a tonne of potentially lethal machinery, barely maintained, driven by a partly trained and often of less than average  skill operator.

Perhaps they should drop the speed limit to 40!  

Ganga

AdrianC said:

Ganga said:

AdrianC said:

fred246 said:

Stop HGVs overtaking. That's what they do in Germany.

Have you ever been to Germany?

BTW, they don't. Not as a blanket. There are some stretches, almost all two-lane, where there's localised bans. As there are on UK motorways...

Are HGV,s not allowed in the second lane of a two lane motorway?

In certain places. As in Germany.
https://goo.gl/maps/tKHw5XBJKBxDqeAS7 for one.
18 month trial became permanent in 2009.
https://www.commercialmotor.com/news/hgv-m-overtaking-ban-becomes-permanent

 Highway Code rule 265 covers it generally.

Also as for trucks being limited to 56 mph , plenty  of them have found a way to bypass this as i have seen trucks doing well over 70 mph.

Massively unlikely. Speed limiters on HGVs are nowhere near as easy to bypass as urban legend claims - and, of course, there would be a massively obvious giveaway with the tacho. In addition, the gearing simply wouldn't allow it.

The trucks are built for world wide use ,i know the steering wheel is on different sides in different countries but some have higher speed limits than the UK also we have limiters to keep the speed down ,if they physically could not go fast due to gearing we would not need the speed limiter.
It would be interesting to hear a truck drivers opion on this.

Ganga

DoaM said:

Ganga said:

AdrianC said:

fred246 said:

Stop HGVs overtaking. That's what they do in Germany.

Have you ever been to Germany?

BTW, they don't. Not as a blanket. There are some stretches, almost all two-lane, where there's localised bans. As there are on UK motorways...

Are HGV,s not allowed in the second lane of a two lane motorway? i thought it was only the outside lane of a three lane motorway that they were prohibited from using.

Notwithstanding the debate regarding nomenclature of lanes on a roadway .... in some instances there can be signage on a 2-lane highway which prevents HGVs from using the "outside" lane / lane 2 for a specified distance. For example on the A1M south of Washington Services before you get to the Durham exit. (Hopefully this Google Maps link works).

I live in Washington and the section you mention is on a long incline that before the restriction was often blocked with a truck taken ages to pass an other one ,i have still seen trucks in the outside lane ,obviously in a hurry and hoping not to get caught by the traffic police. 

MinuteNoodles

AdrianC said:

Massively unlikely. Speed limiters on HGVs are nowhere near as easy to bypass as urban legend claims - and, of course, there would be a massively obvious giveaway with the tacho. In addition, the gearing simply wouldn't allow it.

You've not driven a lorry any time in the last decade have you? Lorries are higher geared than they used to be due to more torque and the higher the engine load the more economical they are. I drive a DAF CF Euro 6 480 6x2 44 tonner. At 56MPH it's doing just over 1000 RPM compared to the 1300-1400RPM the previous generation did at the same speed. Top of the green on the rev counter is 1600RPM, redline is 2100RPM so there's plenty of headroom to have that lorry do 80MPH and still be in the green band.

eamon

In my younger driving days I would have supported a higher speed limit on some motorways and I didn't drive a fast/flash car either. Today I'm quite happy at just under 70 when conditions allow and even then I'm overtaking many motorists. On a long drive I'm more than pleased to arrive at my destination unruffled.