That is a somewhat confused post - mostly correct but seemingly contradictory.
For the purposes of maximising road capacity, *if* the braking distance increases exponentially with speed as per the highway code (my opinion of which is well documented), the optimum speed is about 11mph.
If a road is below maximum capacity, journeys will be shorter at higher speeds.
However, *if* the "two second rule" is applied, rather than the highway code distances, the 'length' of a vehicle effectively becomes shorter (measured in time taken for its length to pass a point), and maximum throughput is just below whatever speed the French cars start to blow up.
HC stopping distances are not the same as the spacing between cars in moving traffic, because the expectation is that the car in front of you is not going to go from <whatever> mph to zero instantly and without warning. The expectation is that a driver will be looking as far ahead as possible and thus see anything requiring braking only a few seconds after the car in front, and that that one will take some time to stop. The HC stopping distances are the same as a 2s gap at 40mph, less below, and greater above.
Re the length of a vehicle, if you add 14.44' to the length of a 2s gap at Xmph then you have the distance between the front of one car and the front of the next, which you use to calculate how many cars will fit onto a given length of road, and the total package of [car+gap] will take a calculable amount of time to pass a point, so that tells you how many can pass a point in a given amount of time.
Suggesting that motorists who have scant regard for often arbitrary temporary speed limits are variously stupid and selfish is perhaps not the best way to ingratiate yourself with a motoring forum - although perhaps that's the idea.
Of course it's not, but I'm not trying to ingratiate myself,
nor should I have to.I'm well aware that this site has a political bias, and that it is one that I do not share, and for the avoidance of doubt, I'm happy to nail my (relevant to this site) colours to the mast.
I am in favour of congestion zones, low emission zones, low traffic neighbourhoods and 20mph speed limits in built-up areas.
I think 15-minute cities are a great idea.
I think that where beneficial to public transport, of course buses etc should be prioritised over private vehicles for road space, traffic light phasing, no entry/right-turn/left-turn/etc signs.
I think that this whole "war on the motorist" idea is complete swivel-eyed conspiracy b******s, believed by people who have swallowed the cynical self-serving lies of populist politicians and the right-wing red tops.
Does this mean that I think cp8759 is "Tory scum"? Of course not.
Does it mean that he, or others, think I'm "socialist scum" and should refuse me their help if I needed it? I would sincerely hope of course not.
[And I'd like to point out, in passing, that the introduction of congestion zones/LEZs/LTNs/etc do not follow party political alignments]
Does this mean that I think the authorities should be allowed a bit of slack in their adherence to the rules and regulations for signage, camera authorisations, notice wording and serving, etc? Of course not. And the flip-side of that is the of-course-not to whether drivers who ignore what they feel are often arbitrary temporary speed limits have right on their side.
As for "stupid and selfish", I wholeheartedly stand by that. How many times do you see posts on various internet fora whinging about a speed limit being reduced when the traffic was light and flowing freely? Stupidity as that tries to deny the reality of a problem 5 miles ahead which is being tackled by reducing the arrival rate of new cars.
How many drivers expect other ones to move left into a gap under 4 seconds long so that they can overtake, and get very headlamp-flashy and aggressive if they don't? Selfish.
Does every driver consider the reality of what the 2s rule means? How long that gap actually is? Extend the principle to doubling it in adverse weather, and think of a line of HGVs doing the legal maximum of 60mpg in the left-lane of a 2-lane motorway or dual carriageway, and a car driver overtaking them at 65mph. A 70mph driver coming up behind him has to recognise that the shortest gap he can possibly pull into is 8 seconds at 60mph which is 704', over ⅛ of a mile. If he doesn't, he's stupid. If he believes that the guy in front should move over even if the gap isn't that long, he's selfish. If he doesn't allow time for the 65mph driver to close in on the vehicle then in front of him, i.e. allow an even longer gap, but expects him to drop his speed to 60 to allow him to overtake, more selfishness.
Look at all the drivers who regard 20mph speed limits, low-emission zones, low traffic neighbourhoods, congestion zones, etc as some ulterior-motive war on motorists to take away their freedoms. Stupid.
Look at all the drivers who decry all those things because they stop them driving what they want, where they want, when they want, and how they want, no matter how popular and proven the benefits are to people who are not motorists. Selfish.
Sorry, Andy, but there really are a lot of stupid, selfish motorists out there.
Temporary limits at rush hour to maximise traffic flow are largely a good idea, let down by the prevalence of arbitrary and pointless speed limit reductions 'just in case'.
Do you know that they are arbitrary and pointless, or is it just that their point is obscure to you because you don't have knowledge of all the facts?
Do you not believe that prevention is better than cure?
Today Aesop would be castigated for his portrayal of the boy on the grounds that there might have been a wolf anyway, and you can't be too careful. You can,
Every mile of road reduced to 50 from 70 because on balance it is judged to be beneficial "costs" you 21 seconds.
21 seconds.
What kind of life do you lead where that is a burden too onerous to bear?
A 10-mile stretch costs you less time than it takes to make a cup of tea.
and that is why temporary speed limits to increase traffic flow don't work.
There is a sound theoretical basis for them, and they might be more effective if there was greater observance of them.
Plus, "work" has to be viewed as the aggregate effect on tens of thousands of motorists over several miles and a time possibly measured in hours, not just one person's individual experience of a few miles at the cost of a few minutes.