mandatory speed limiters to be fitted from 2022?
Discussion
NMNeil said:
Doubtful. If some can't grasp what the 30 and 20mph signs mean then just replacing them with a big 10 mph sign will also be met with the same comprehension issues for some.
Some? Last time I checked around 96% of traffic was speeding in 20mph zones. Those who adhere to 20mph limits are the weirdos, not those who break them.Kawasicki said:
NMNeil said:
Doubtful. If some can't grasp what the 30 and 20mph signs mean then just replacing them with a big 10 mph sign will also be met with the same comprehension issues for some.
Some? Last time I checked around 96% of traffic was speeding in 20mph zones. Those who adhere to 20mph limits are the weirdos, not those who break them.
king great queue of frustrated motorists behind me. Feels very righteous. 10mph zones would be even more satisfying 
Kawasicki said:
Some? Last time I checked around 96% of traffic was speeding in 20mph zones. Those who adhere to 20mph limits are the weirdos, not those who break them.
In London? I set my cruise control for 23, I think my true speed is a bit lower, and that seems to fit quite well with the speed of the traffic when not in congestion and on roads suitable for 30 plus. As a regular user of Finchley Road in and out of town from the A1 I am maddened by the recent reduction of the limit on it to 20. There is one benefit of the spread of 20's - soon we will know that the in town limit is 20 everywhere and no longer have to concentrate on whether the limit is 20 or 30.waremark said:
Kawasicki said:
Some? Last time I checked around 96% of traffic was speeding in 20mph zones. Those who adhere to 20mph limits are the weirdos, not those who break them.
In London? I set my cruise control for 23, I think my true speed is a bit lower, and that seems to fit quite well with the speed of the traffic when not in congestion and on roads suitable for 30 plus. As a regular user of Finchley Road in and out of town from the A1 I am maddened by the recent reduction of the limit on it to 20. There is one benefit of the spread of 20's - soon we will know that the in town limit is 20 everywhere and no longer have to concentrate on whether the limit is 20 or 30.king bedlam when you have 2 cars at 20 "overtaking".TX.
Terminator X said:
Wimbledon has a blanket speed limit of 20 even on DC's. It causes fking bedlam when you have 2 cars at 20 "overtaking".
TX.
At least the council has bumped Kingston Rd to 30mph, rather than 20 like it was for a while! I still think that 20mph road was pretty much the reason why most drivers disregarded every other 20 speed limit, given it was a 40mph two-lane dual carriageway before and suddenly you're being overtaking by cyclists on their dedicated cycle lane adjacent to the carriageway!king bedlam when you have 2 cars at 20 "overtaking".TX.
The 20 roads in the residential areas make sense, I have no complaints there. However on more open roads (e.g. Worple Rd), well, if even the f
king buses are doing 30 down there, nobody's going to pay any attention to the speed limits. It just devalues the 20mph speed limits where they're actually of benefit, which is counter-intuitive to their introduction in the first place - but hey, that needs thinking about something more than once. 
heebeegeetee said:
Terminator X said:
Edit - oh and you can see why they are picking on cars 
I think you can if you look at numbers rather than rates. 
Plus you have to ask who is killing pedestrians, if not cyclists.
As for poor buggers on bikes and motorbikes, the majority of incidents that I've seen over the years where it hasn't just been the biker overcooking it have been cars simply pulling out of a side road or out from the side of the road without looking and taking out another road user who was behaving perfectly correctly.
Most incidents I see where a car nearly hits a cyclist doesn't involve any speeding. It's normally a deliberate decision to intimidate the more vulnerable road user or the usual Fat Beryl/Barry away with the fairies.
None of the stuff be proposed to curb and control everyone really addresses either the known causes or the known offenders.
bigothunter said:
Kawasicki said:
NMNeil said:
Doubtful. If some can't grasp what the 30 and 20mph signs mean then just replacing them with a big 10 mph sign will also be met with the same comprehension issues for some.
Some? Last time I checked around 96% of traffic was speeding in 20mph zones. Those who adhere to 20mph limits are the weirdos, not those who break them.king great queue of frustrated motorists behind me. Feels very righteous. 10mph zones would be even more satisfying I've the same issue in 50s in that that's the speed where most old slush pumps lock up so it's about the least economical speed around that level.
The latter is my issue but surely few modern cars have been optimised to be most efficient at 20?
DonkeyApple said:
Are cars even optimised to run at 20mph?
Most petrol or diesel cars at at their optimum around 30mph.With combustion engines, at slower speeds it is likely that all kinds of drivetrain, friction, alternator, aircon, pump and other relatively constant losses are consuming quite a high percentage of what the engine is producing.
I can imagine electric cars might be optimal at slightly slower speeds but I have no data on that.
DonkeyApple said:
Are cars even optimised to run at 20mph? My cars need to be in second gear and are very clearly pumping out much more crap than if they were pottering at 30.
I've the same issue in 50s in that that's the speed where most old slush pumps lock up so it's about the least economical speed around that level.
The latter is my issue but surely few modern cars have been optimised to be most efficient at 20?
EVs are suited to low speeds simply because they are efficient across the whole load/speed range. I have not seen any data but suspect 20mph is about optimal for an EV.I've the same issue in 50s in that that's the speed where most old slush pumps lock up so it's about the least economical speed around that level.
The latter is my issue but surely few modern cars have been optimised to be most efficient at 20?
But go slow enough and ancillary loads dominate, so the dominant factor becomes journey time not speed. 10mph would be a disaster for both ICE and EV (especially ICE emissions).
RVB said:
Most petrol or diesel cars at at their optimum around 30mph.
With combustion engines, at slower speeds it is likely that all kinds of drivetrain, friction, alternator, aircon, pump and other relatively constant losses are consuming quite a high percentage of what the engine is producing.
I can imagine electric cars might be optimal at slightly slower speeds but I have no data on that.
30mph sounds too slow for optimal ICE fuel consumption and emissions. But being opened minded, I would appreciate data which supports 30mph for efficiency. Do you have anything please?With combustion engines, at slower speeds it is likely that all kinds of drivetrain, friction, alternator, aircon, pump and other relatively constant losses are consuming quite a high percentage of what the engine is producing.
I can imagine electric cars might be optimal at slightly slower speeds but I have no data on that.
Classic curve shows optimum ICE efficiency at about 55mph cruise. But that's American data for huge cars and awful low speed consumption.
More recent European data for smaller ICE cars shows optimum efficiency around 43mph. ICE suffer from poor light load efficiency. Petrols are affected more than diesels (ref BSFC maps).
Unlike EVs where I guess 20mph is around optimal. Going even slower cocks up both ICE and EV, so expect 10mph limits anytime soon
Gassing Station | General Gassing | Top of Page | What's New | My Stuff