Unpopular but necessary policy on speed limits?...

[Nick]

It was to reduce accidents in a time when there were no speed limits outside of built up areas.
https://hansard.parliament.uk/Commons/1967-07-12/debates/2fc0c1b8-1e1d-4618-bad1-48bd158c682f/Roads(70MphSpeedLimit)

Lane discipline would be welcome and improve matters for all, but I feel were i to suggest "stay in lane" zones enforced by ANPR cameras you would shout about it being antidemocratic and your god give right as an englishman to switch lanes as often as you please

It would also drift away from the central thrust.

Efficiency is crucial to EVs as it allows them to provide useful range with a smaller (thus cheaper) battery. A Citroen Oli (concept) can go about 250miles on a 40kwh battery.  A Hummer EV can manage about 200 on a 200kwh battery. A Citroen Ami which is legally limited to 30mph can get 50miles from less than 6kwh

If we are to switch away from ICE cars we need to make sure the vehicles are as efficient as possible

The government could tax vehicles based on the Cda values or battery size or all sorts of things to encourage energy efficiency.  However one that would not only make a big difference but would also help with the remaining fleet of ICE vehicles as they age out is to reduce motorway and dual carriageway speeds to 50mph.  Weight limits and taxes would also help.

The future of cars should be more like the Citroen Oli concept (top speed 60mph)

than the Hummer EV (top speed 106mph)


(and before you go nuts, i used the Oli concept because it is similar in form to the hummer.  The actual detail of the looks and styling are not important - or to my mind that appealing - it is the concept that you don't need a 3 ton, 106 mph vehicle to achieve what you can with a 1000kg, 60mph vehicle)

How do you know a Citroen can do 250 miles?

[Red Rackham]

I used to drive a lot, my ex wife and kids lived on the south coast I lived in Staffs. It was nearly a 400 mile return trip. During the day it was a nightmare 5 or 6 hour trip one way and that's after the Newbury bypass opened, before then I could expect to spend an hour just getting through Newbury. That bypass was so necessary, if I could have got my hands on that swampy chap I'd have fekin throttled him.

I didn't go down to Bournemouth often, three or four times a year. But I soon stopped doing that trip during the day. Leaving at midnight I could be back home in six hours. At night the roads were empty and it was all fast roads motorway and A34 and at night time you can safely cruise at 90 to 100 because apart from lorries on the inside lane theres nothing on the road.

I cant imagine that trip with an electric car. Actually, with the insane speed restrictions lefties are imposing it would have probably been a two day trip. Progress? I think not. Those were the good old days when you could put your foot down, before there were cameras everywhere. I don't have to travel to Bournemouth any more, it's bittersweet. And I'll never by an electric car.

[BeElBeeBub]

Unlike the Yanks, there are reasons why the Brits do things, usual through experience over the years. There will be a reason we drive at 70 on motorways, there's a reason why we drive on the left.

It was to reduce accidents in a time when there were no speed limits outside of built up areas.
https://hansard.parliament.uk/Commons/1967-07-12/debates/2fc0c1b8-1e1d-4618-bad1-48bd158c682f/Roads(70MphSpeedLimit)

How about you put effort into lane discipline, there was a new law brought in a few years ago where people can be fined for bad lane discipline, I've never seen anyone done for it.

Lane discipline would be welcome and improve matters for all, but I feel were i to suggest "stay in lane" zones enforced by ANPR cameras you would shout about it being antidemocratic and your god give right as an englishman to switch lanes as often as you please

It would also drift away from the central thrust.

Efficiency is crucial to EVs as it allows them to provide useful range with a smaller (thus cheaper) battery. A Citroen Oli (concept) can go about 250miles on a 40kwh battery.  A Hummer EV can manage about 200 on a 200kwh battery. A Citroen Ami which is legally limited to 30mph can get 50miles from less than 6kwh

If we are to switch away from ICE cars we need to make sure the vehicles are as efficient as possible

The government could tax vehicles based on the Cda values or battery size or all sorts of things to encourage energy efficiency.  However one that would not only make a big difference but would also help with the remaining fleet of ICE vehicles as they age out is to reduce motorway and dual carriageway speeds to 50mph.  Weight limits and taxes would also help.

The future of cars should be more like the Citroen Oli concept (top speed 60mph)

than the Hummer EV (top speed 106mph)


(and before you go nuts, i used the Oli concept because it is similar in form to the hummer.  The actual detail of the looks and styling are not important - or to my mind that appealing - it is the concept that you don't need a 3 ton, 106 mph vehicle to achieve what you can with a 1000kg, 60mph vehicle)

[Nick]

I'm not sure you understand democracy. Presumably you ignore all speed limits as they are an affront to your democratic right to drive at whatever speed you like on public property? You don't wear seat belt either and drive after a dozen pints.

Limjts.already exist, your 1000bhp plaid is limited to 70mph on the roads. It must have seat belts, which you must wear. You must not have more than the stated amount of blood alcohol to drive it on the road etc.

I am just suggesting the limit be 50 where it is currently 60 and 70.

Unlike the Yanks, there are reasons why the Brits do things, usual through experience over the years. There will be a reason we drive at 70 on motorways, there's a reason why we drive on the left. How about you put effort into lane discipline, there was a new law brought in a few years ago where people can be fined for bad lane discipline, I've never seen anyone done for it. 

[BeElBeeBub]

It's clear you do not understand democracy. I don't want someone telling me what car spec I will have, if I want to go out and buy a 1000HP Plaid then I expect to be able to do so. I don't want anyone telling me I can't, it's just another referendum that would have to be played out. If you can't see that then it's pointless chatting with you.

I'm not sure you understand democracy. Presumably you ignore all speed limits as they are an affront to your democratic right to drive at whatever speed you like on public property? You don't wear seat belt either and drive after a dozen pints. 

Limjts.already exist, your 1000bhp plaid is limited to 70mph on the roads. It must have seat belts, which you must wear. You must not have more than the stated amount of blood alcohol to drive it on the road etc. 

I am just suggesting the limit be 50 where it is currently 60 and 70. 

[Nick]

The point is that car makers design to the limits set.

See Kei cars in Japan.

Cars that are designed for maximum speeds of 50 can be cheaper and more efficient with longer range than if they are designed for 70.

By removing the need to design for 70 and imposing limits to prevent car bloat we all end up with cheaper cars that can travel further with similar, if not better, journey time to now.

Cars are getting bigger and heavier. Detractors like to claim this as a disadvantage of EVs but in reality the increase in size and weight is happening because of car makers profit motives, especially in the US.

An EV designed to travel at 70mph will be bigger, heavier and more expensive than one designed to travel at 50mph for the same range.

But driving at 50mph is unpleasant and dangerous when people are zooming past at 70+ in SUVs

Whilst driving at. 50mph in a lighter car is perfectly pleasant when everyone else is.

The only people who lose out are arseholes who can longer compensate for tiny dicks by driving +2ton ego boosters at 90mph.

It's clear you do not understand democracy. I don't want someone telling me what car spec I will have, if I want to go out and buy a 1000HP Plaid then I expect to be able to do so. I don't want anyone telling me I can't, it's just another referendum that would have to be played out. If you can't see that then it's pointless chatting with you. 

[BeElBeeBub]

I've made my point about extra congestion, I don't think any of it has been negated. I don't see why the whole motorway should be reduced to 50. If people want to travel at 50 mph they are perfectly entitled to do so. I'm not recommending it, though.

The point is that car makers design to the limits set. 

See Kei cars in Japan. 

Cars that are designed for maximum speeds of 50 can be cheaper and more efficient with longer range than if they are designed for 70.

By removing the need to design for 70 and imposing limits to prevent car bloat we all end up with cheaper cars that can travel further with similar, if not better, journey time to now. 

Cars are getting bigger and heavier. Detractors like to claim this as a disadvantage of EVs but in reality the increase in size and weight is happening because of car makers profit motives, especially in the US. 

An EV designed to travel at 70mph will be bigger, heavier and more expensive than one designed to travel at 50mph for the same range. 

But driving at 50mph is unpleasant and dangerous when people are zooming past at 70+ in SUVs

Whilst driving at. 50mph in a lighter car is perfectly pleasant when everyone else is. 

The only people who lose out are arseholes who can longer compensate for tiny dicks by driving +2ton ego boosters at 90mph.

[BeElBeeBub]

As i said, the 50 stretches of the m4 are NEVER able to do 50 nothing whatsoever to do with phantom jams which actually are MORE to do with assholes CHANGING LANES when they see a camera, causing the guy behind to do a WTF than the camera itself, you DONT get PHANTOM jams at the M32 you get real ones

i'm giving up. You keep thinking its caused because of what you think it is and i will stick to knowing the truth

I'm agreeing with you! Lane changing excessively causes phantom jams, which in turn bugger the capacity and journey speed of motorways.

A 50mph limit (enforced by Ave speed cams and, if necessary limiters in vehicles, trivially easy with electric cars) would not increase congestion over the current regime. 

[Barry]

I've made my point about extra congestion, I don't think any of it has been negated. I don't see why the whole motorway should be reduced to 50. If people want to travel at 50 mph they are perfectly entitled to do so. I'm not recommending it, though.

[johnofgwent]

Which is my point, when you are on an mway or dual carriageway driving at the prevailing speed (often more than 70) burns through your battery, and your time from A to B is knackered by the phantom jams caused by high speeds and lane switching, and yes speed cameras do cause that as idiots slam on the brakes to avoid being flashed. Thus leading to the absolute worst drivinf style for range - high speed bursts with heavy braking and acceleration.


Again anecdotes aren't data but phantom jams seem very rare in 50mlh average speed zones. In fact I would do away with point speed cameras, especially on motorways. I'd replace them with average speed cameras zones

As i said, the 50 stretches of the m4 are NEVER able to do 50 nothing whatsoever to do with phantom jams which actually are MORE to do with assholes CHANGING LANES when they see a camera, causing the guy behind to do a WTF than the camera itself, you DONT get PHANTOM jams at the M32 you get real ones 

i'm giving up. You keep thinking its caused because of what you think it is and i will stick to knowing the truth

[BeElBeeBub]

I know all about phantom jams. They started at about the same time speed cameras appeared on the M25 and were for the main part caused by drivers switching lanes to avoid idiots braking at cameras they were not actually speeding past

Have you ever DRIVEN an EV

As a former owner of one the power consumption when you go above 45 interesting.

Which is my point, when you are on an mway or dual carriageway driving at the prevailing speed (often more than 70) burns through your battery, and your time from A to B is knackered by the phantom jams caused by high speeds and lane switching, and yes speed cameras do cause that as idiots slam on the brakes to avoid being flashed. Thus leading to the absolute worst drivinf style for range - high speed bursts with heavy braking and acceleration. 


Again anecdotes aren't data but phantom jams seem very rare in 50mlh average speed zones. In fact I would do away with point speed cameras, especially on motorways. I'd replace them with average speed cameras zones 

[BeElBeeBub]

Increased capacity on the roads has no beneficial effect on how quickly I travel from A to B, it merely introduces more crap drivers likely to cause a butterfly effect per Sq Mile.  

The central point of my suggestion is not capacity - bit is about improving the efficency of EVs so that they can achieve longer ranges with smaller batteries. We could build such vehicles today *but* they woiod have to share road space with vehicles doing 70+, and crucially, designed for speeds far in excess of 70.  Driving a 2cv at 50 on a motorway whilst range rovers and other 2tpnnplus SUVs thunder past at 80 is unnerving and unpleasant, not to mention unsafe. Driving one at 50 when everyone else is driving at 50, in similarly less ridiculously oversized vehicles would, I imagine, be much more pleasant. 

The capacity question merely arose because a poster asked if I had considered the reduction in capacity a lower limit might cause. My answer was yes I had considered it, but believe there woukd be no reduction and even an slight increase. 

As for your assertion about the butterfly effect (I assume you mean phantom jams) :

You are correct, the closer a road is to capacity the higher the chances of "butterfly effect", which is why reducing speed (and ideally enforcing with average speed checks) woiod reduce these events. For the same number of cars per hour a 50mph road is at a lower proportion of it's capacity than it woiod be at 70mph.  

So I would argue that your A-B travel times would be similar (on average) in a 50mph scenario to a 70mph scenario.

I used to regularly travel 150miles from London to my in laws. My driving speed is considerably less "press on" than my wife's. I rarely exceeded 70 whilst she was, let's say, more lead footed. Our journey times were nearly the same, about 3 hours. If the roads were very clear she might be 2.50, maybe 2.45.  Phantom jams and congestion were the biggest determinates. 

That said there was one occasion after midnight in a company car, when I was in a hurry, the journey was considerably shorter. I those scenarios the A-B time is obviously shorter with higher speed limits, but I would suggest in those circumstances the actual speed limit is less important than the mehanical and practical one. 

As for your efficiency statement, it's way off. For a start, EV's are almost twice as efficient as ICE's, so travelling fast in an EV is less fuel hungry by far than an ICE, also ICE's cannot regen like an EV. The reason for this is how an inverter works: an EV can produce 100% torque at zero speed and once moving fast only powers the losses through very tight PID control. An ICE uses an MAF to measure air flow and a lambda sensor fitted in the exhaust to analyse the exhaust gas to see how much unburnt fuel is present. On cruise control the fuel is steadily backed off until the car starts to slow and then a bit more is added to maintain speed. The PID loop has a very long integral time making it a very inefficient system on an ICE. on an EV the feedback is done via encoders making the adjustments almost immediate, a very efficient system, so increases in speed do not have the effect that is suffered by ICE's. I've worked on inverter drive systems for 30 years, I know the subject very well.

Yes, I too am familiar with both inverters and ICE engine control strategies. 
But this reinforces my point - both BEV and ICE cars are more efficient in free flowing 50mph conditions than 70mph.

And yes BEVs don't suffer from the poor efficency at low speeds that ICE cars do, but they are more affected by the efficency drop at higher speeds. 

With ICE vehicles providing power is expensive (a buffer more complex motor) but range is cheap (a bigger fuel tank) so zooming around inefficently isn't a major problem.

EVs power is (relatively) easy but range is more expensive.

Hence my suggestion that a 50mph limit woukd allow improved range without the "2CV in the slow lane" experience. 

[johnofgwent]

Go on, prove it.....

Pretty much every time I"ve been in a 50mph average speed zone, typically roadworks on mways, the traffic flow has been better than the unrestricted parts. (anecdotes aren't data)

I've venture the traffic at 70mph is being snarled up by the fact it is 70mph traffic.

Phantom jams occur when people leave insufficient space between cars and a simple braking manouver cascades into stopped traffic.

The minimum distance to avoid this increases with speed.

Typically cars need to have a larger distance between them the faster the traffic flow. This distance is time based eg"the 2 second rule". Capacity is number of cars per minute. The faster the traffic the fewer cars you get per minute.

The slower the cars the shorter the gap can be (down to a minimum value) and the higher capacity.

I know all about phantom jams. They started at about the same time speed cameras appeared on the M25 and were for the main part caused by drivers switching lanes to avoid idiots braking at cameras they were not actually speeding past

Have you ever DRIVEN an EV 

As a former owner of one the power consumption when you go above 45 interesting.

[Nick]

Capacity is important as the poster asked the question about the lower speed limit affecting capacity

It doesn't, if anything it improves it.
Now that is a ridiculous statement. I was not claiming that lowering the speed increases the capacity indefinitely. Notice the curve starts to bend back on itself below about 30kph? That's because, as you said, the capacity at 0kph is zero.

If you want to maximise the capacity, that is the number of cars per hour that can travel down it, of our motorway system the speed limit should be about 30kph.

50mph will not reduce the capacity of the motorway or trunk road network *and* will increase the range of electric (and ICE) vehicles by about 40%. In turn the lower maximum speeds would allow BEVs to be built lighter (and cheaper) which will further improve range. The increased efficency effectively boosts charging speeds as the "miles per minute charging" figure is higher.

Increased capacity on the roads has no beneficial effect on how quickly I travel from A to B, it merely introduces more crap drivers likely to cause a butterfly effect per Sq Mile. As for your efficiency statement, it's way off. For a start, EV's are almost twice as efficient as ICE's, so travelling fast in an EV is less fuel hungry by far than an ICE, also ICE's cannot regen like an EV. The reason for this is how an inverter works: an EV can produce 100% torque at zero speed and once moving fast only powers the losses through very tight PID control. An ICE uses an MAF to measure air flow and a lambda sensor fitted in the exhaust to analyse the exhaust gas to see how much unburnt fuel is present. On cruise control the fuel is steadily backed off until the car starts to slow and then a bit more is added to maintain speed. The PID loop has a very long integral time making it a very inefficient system on an ICE. on an EV the feedback is done via encoders making the adjustments almost immediate, a very efficient system, so increases in speed do not have the effect that is suffered by ICE's. I've worked on inverter drive systems for 30 years, I know the subject very well.

[BeElBeeBub]

Capacity means nothing, that's the most ridiculous thing to say.

Capacity is important as the poster asked the question about the lower speed limit affecting capacity

It doesn't, if anything it improves it.

Let's take the speed all the way down to zero and have every car touching, you can't get capacity any bigger, no one is moving!! 🙄

Now that is a ridiculous statement. I was not claiming that lowering the speed increases the capacity indefinitely. Notice the curve starts to bend back on itself below about 30kph? That's because, as you said, the capacity at 0kph is zero.

If you want to maximise the capacity, that is the number of cars per hour that can travel down it, of our motorway system the speed limit should be about 30kph.

50mph will not reduce the capacity of the motorway or trunk road network *and* will increase the range of electric (and ICE) vehicles by about 40%. In turn the lower maximum speeds would allow BEVs to be built lighter (and cheaper) which will further improve range. The increased efficency effectively boosts charging speeds as the "miles per minute charging" figure is higher.