Distances on the UK motorways (and major, dual carriageway A roads) are quite easy to estimate - if you've got a clear view of the hard shoulder: every 100m there's a post to tell you the direction of the nearest emergency phone. At 70mph, the stopping distance given by the Highway code is 315ft or 96m - or approximately the distance between these posts! (That stopping distance is years old and car brakes have improved much since then; however, when I did my PCV [coach] test, they were the stopping distances for the fully laden coach! - up to 23 tonnes for the coaches I've driven.)
However, the highway code suggests that a 2 second gap is sufficient for fast roads as the probability of coming across a static object is much less and also, your braking can overlap with the vehicle in front: the highway code suggests that a distance (in ft) equivalent to the speed of the vehicle (in mph) will be passed before braking is applied (the "thinking distance"). If you're travelling at the same speed as the vehicle in front and have a 2 second gap (the "thinking time" is less than one second), you'll have moved closer to the preceding vehicle, but your braking will still start at a place further back on the road, assuming you start to reach when you see their brake lights (the shock way can bee seen moving back up the traffic flow by the brake lights coming on) - even at 2 seconds to think, you'll start braking at approx the same place on the road.
The problems occur when not enough room is left. That is when over reacting and harsh braking occurs, ieeg if you are past the point where they started to brake.
your chance of getting ripped-off by the casino is about zip
Surely that would depend upon your meaning of "ripped-off".
If by being ripped-off, you mean not being offered the correct odds, then all casinos are ripping you off. Take, for example, Roulette: the odds are worked out correctly if there were no zeros on the wheel; eg on a single number there the odds are 37 to 1 that the ball won't land on your number (36 numbers + 2 zeros), but you only get paid at 35 to 1. Your expectation at roulette is -5 5/19%, ie for every $1 you bet, in the long run you can expect to receive approx $0.95 back.
If by being ripped-off you mean being cheated, then yes. (Things like gaffed roulette wheels whereby the ball can be directed to avoid numbers, etc).
My advice if you must gamble in a casino: play Blackjack - the odds are constantly changing as each card is dealt and at times actually favour the player. (There is still a possibility of cheating with the dealing of the cards.)
Yes - most of Terry Pratchett's Discworld series of books have no chapters (as such...just an occasional "next level" line of asterix as the bottom of a page). It was actually useful in my previous job where I could get a few minutes to read the books at a time - having no chapters as such meant that it was actually easier to stop for the time I needed to work between breaks and to pick up again soon afterwards; though it also had the disadvantage that I could end up reading for hours right through a book in one go (instead of doing other needed things - like sleep).
I must admit to not having played many recent games, but I do remember playing games of both styles. Level games had the advantage in that there was a definite break when the game could be stopped (and saved) and restarted easily at a later time, but with non-levelled games, restarting a game after a break would leave me disorientated for a few, sometimes vital, moments whilst I got back into where I was in the game. (At least with the books, I could easily refresh my memory by quickly skimming over the previous paragraph or two.)
But is that available at the point of sale where the sales contract is made?
I have often made spur of the moment purchases with no prior knowledge of the publisher and with no internet access available; am I expected to visit every software publisher's website to check out the EULA of every piece of software on the offchance that I may see it offered for "sale" and decide the "buy" it?
I was told when recently "purchasing" some software that it was only licenced (and would refuse its return if the package was opened). However, there was no clear licence available on the package (only readable by opening said package in which case the shop would refuse a refund - I don't know how legal that would be), nor at the till to explicitly tell me what the licence was.
Incidently, on installing one of the pieces of software it came up with a message that the software was only licenced, not bought; it then came up with a message "thank you for buying this software". (Not buying a licence to use the software.) If the software (installer) publisher can't decide whether it is bought or not and tells us two conflicting statments regarding that, how can the rest of us know?
Well, there is a sort of prior art in [the good ol' ASCII graphic'd *nix] Larn: after collecting gold and treasure on the way to getting the specific potion, depositing some of said gold in the bank, etc, once you had found the potion and completed game you'd get emails from the game requesting you pay your taxes! (Obviously in games funds.)
So re-instate the demand for a working model that the Patent Office used to require. If "people" want software patents, then the "device" is software and so a software implementation (including source code) should be provided as a working model which would then be available for anyone querying the patent to view.
The "storage" for software patent working models won't be the problem that the storage of a [physical] working model requires (which caused the cessation of said need) as I'm sure a modern Hard disk could store many software patent source codes.
Creating working models with software is probably much easier than with physical inventions, therefore I can see no reason not to demand a working implementation.
Maybe, but whilst awaiting tral, a person is encarcerated in jail - with their freedoms of movement, action, normal everyday business, etc curtailed, unless bail is paid; whilst corporatons are awaiting trial are they incarcerated, unable to do normal everyday business, unless they post bail - do they even post bail?
In the UK, at least, it would appear to be in breach of Section 1 of the Computer Misuse Act 1990:
1 -- (1) A person is guilty of an offence if--
(a)he causes a computer to perform any function with intent to secure access to any program or data held in any computer;
(b)the access he intends to secure is unauthorised; and
(c)he knows at the time he causes the computer to perform the function that that is the case.
The data sent home is noted by (a). As the user has expressly not agreed to the WGA EULA, unauthorised access is noted by (b) and (c) - in particular (c) as there was no agreemnt to the EULA; assuming of course that the data sent home is that that would be sent home IFF the EULA had been agreed and WGA installed.
As an aside, the Sony rootkit that installed something even when the EULA or whatever was decined was probably in breach of Section 3 of the same Act - doing "...any act which causes an unauthorised modification of the contents of any computer..." - those discs weren't sold in the UK?
The question is who is the responsible entity for a company: they have programmers that have written the code that does the unauthorised access (are they responsible), or is it their managers (who defined the specs) or the company as a whole (the directors)?
Hmmm...I never realised stealing other people's copyright was a right.
The only licence you have to use someone's code is the licence they give you. If you don't understand their licence, then you should at least look at copyright law. That, I'm sure, is rather explicit that you can't just take stuff, eg open-source program, someone has written and use it in any way you please, eg in a closed-source program. If you don't fully understand the GPL, then contact the author as to his/her requirements for use of their code; if you can't make contact then assume Copyright Law - the GPL gives extra rights that Copyright Law doesn't and all you would lose is those extra rights.
They're basically saying "You did something wrong but I'm not telling you what you did and you have to make up for it or else."...
Where have I heard something similar recently...
...This is just plain extortion and should be dealt with as such.
So why hasn't SCO been done for extortion yet? It's only been, what, 3 years(?) or so that they're refused to identify the "millions of lines" of infrnging code in Linux; AND they sent out letters demanding a $699 licence (to use their IP or risk being sued) to Linux users. (or something like that)
I'm sure that the DOJ investigation into MS's practices and monopoly position came up with a breakup solution (separating the OS and applications divisions so that, for example, MS applications would not have the inside information of undocmented APIs, but would be forced to use the publically documented ones and so compete on merit), but it never happened, etc.
Alternatively, arrive 30 minutes after the advertised start of the film - last time I went to the cinema, due to delays at the pizza place we went for food (sic) before seeing the film, that's just what we did: we arrived just as the film we wanted to see was starting (we had purchased our reserved seats (as all the seats in the cinema were) before going for our food) and missed all the ads, trailers and anti-copyright infringement notice.
What really annoys me is the 30 second unskippable ad expounding (erroneously) piracy as theft ("...you wouldn't steal a movie? downloading is stealing...") on a DVD I legally purchased is actually stealing from me: my time (the 30 seconds of the ad - they haven't paid me for their advertising) PLUS the electricity required to power my DVD player during that period, plus (though not absolutely necessary as I could turn them off - which then makes the ad useless!) my TV & surround sound system. So far they have stolen around 15 minutes of my time and electricity.
So maybe he'll be sentenced to 101 concurrent 1 year sentences totalling 1 year in jail all together.
As long as he commited those 101 offences concurrently, at exactly the same time. The sentences should overlap timewise similarly to the orignal offences: commit 1000 offences, get 1000 years for them (1 each); commit 100 at a time, so take 100 sentences together to give 10 years to execute the punishment. Simple really. Now how many people were spammed with how many messages each over what period of time? Based on the amount of spam I have received this year so far, and the amount of repeat (different timed) spam, that makes...100,000+ years at a guess...at 101 years he's getting off lightly, and that's for the spamming only - not taking into account the other offences.
And "first to file/first to invent" only covers when two people/companies file a patent at around the same time without any previous public disclosure of their work. (e.g. they both developed the same thing independently
Surely this given example is a reason the patent should be rejected as obvious - two independent people [versed in the art] have come up with the same invention?
Re:I've been using vi for so long...
on
The Birth of vi
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· Score: 1
The colon prefix to commands in vi is actually accessing ex commands (FWIU).
The one thing I miss in vim is the inability to use term=dumb that vi could - vi would display only the current line in the buffer and normal screen movement commands would be sensibly mapped[1]; the only cursor control vi required for term=dumb was ^M (carriage return = goto start of line, adding ability to do ^H (backspace) improved speed of use as going left 1 char used that as opposed to ^M{line upto char}.
[1]I've used vi over a 300 baud modem link on a glass yty (=dumb terminal that only understood cursor controls ^M & ^H) and it was most usable. [One of the commands was mapped to display the context of the current line by showing the previous 10 lines, the current line and the following 10 lines.]
if everyone made a real attempt to find a comfortable merging point without disrupting the lane's flow
They have; and the best, single, one is the pinch point with the lanes merging in turn - as people approach it, matching speed next to a gap. The point of the 5 mile warning is obviously because they expect so much traffic that queues are inevitable so that it gives everyone a chance to slow down so that the queues of traffic can merge safely and smoothly - easing off the gas before the pinch point allows the traffic in both lanes to be moving at the same speed and to sort themselves into cog-position (with vehicle next to a gap), so that when they merge, they need no further slowing, do so smoothly and are travelling at whatever the limit is through the constriction (roadworks often have a lower limit through them).
You're forgetting that the capacity of the road is usually based on how many vehicles can fit along it, ie vehicles/lane-mile - and as speed reduces, there is need for less gap between vehicles and so more vehicles can fit per lane-mile; the flow is the number of vehicles that pass by in a given time. Congestion occurs when there is not enough road space for the vehicles.
Braking distances given in tables are based on square of speed. As speed reduces, so does braking distance. If the stopping distance as given by such tables is left between vehicles, the time between vehicles will also change (eg at 20mph, dist=40ft which is ~1.4secs; at 70mph, dist=315ft, which is ~3.1secs). At just below 40mph (38 2/3mph) the braking distance given by the table actually takes 2 seconds. So above about 40mph, the 2 second separation rule is giving less than the stopping distance between vehicles, but those speeds are [usually] reserved for "fast" roads where something isn't really expected to "jump out" and cause the preceding vehicle to stop instantly, so the thinking and braking distance an overlap the vehice in front - in the time it takes you to react, the preceding vehicle will [usually] have moved forward [relatively] quite a way.
So how does reducing the speed improve the capacity, and flow?
The maximum capacity is when there is zero gap between vehicles, ie their speed is zero, but that is the worst case flow (also zero).
So what about 70mph & 60mph? Assuming a car of about 15' length and a separation of 2 seconds:
So although the speed has been reduced by 15%, the flow has only been reduced by barely 1%; but the capacity of each lane-mile has increased by about 16% - an extra 4 cars are able to use each mile of each lane of the road.
If the stopping distance is left between vehicles: at 70mph, the cs is 315+15=330', allowing 16 c/lm, or 1,120 cars/hour; at 60mph, the cs is 240+15=255', allowing ~21 c/lm, or 1,242 cars/hour. So by reducing the speed by 15%, in this case the capacity has increased by about 29% (5 extra cars/lane-mile) and the flow has increased by almost 11%!
If you do the maths, you'll find the optimum speed for the max flow when the stopping distance is left occurs when speed = sqrt(20 * mean_length_of_vehicle)! So the more longer vehicles there are, the faster the speed for optimum flow - so be grateful for all the coaches and arctics.
At 70mph, 2 secs is approx 205ft. According to the UK Highway code, the average car length is 4m, or about 13ft, so leaving 2 secs between cars leads to a front bumper to front bumper distance of 205 + 13 = ~220ft which allows for 5280/220 = 24 cars/lane-mile.
Just remember that the UK has a much smaller area than the US; and our cars are much smaller.
Incidently, when I did my PCV (bus driving) test 12 years ago, these typical stopping distances were the ones I was expected to know for the coach.
Optimum braking is effected when the wheels are just about to lock and a skid is about to start. I don't know about you, but I certainly can't manage that whereas ABS can.
However, in most circumstances, you won't be braking that close to skidding and ABS will actualy have no effect on your braking distance - all it will (usually) do is provide you with control in that you'll be able to steer which would normally lower the point at which a skid would start, and so enable you to still stop safely whilst steering round obstacles. [I think - IANAME: I Am Not A Mechanical Engineer ^_^]
In the UK, 315ft is actally quite easy to roughly visualise on the motorways (to an accuracy of about 13ft, or 4m) - 315ft is approx 96 metres. Along the side of the motorway are numbered marker posts (that point to the nearest emergency telephone): they are 100m apart. 315ft is slightly less than this, so use the marker posts (as an approx over estimate).
Slashdot Mirror
Distances on the UK motorways (and major, dual carriageway A roads) are quite easy to estimate - if you've got a clear view of the hard shoulder: every 100m there's a post to tell you the direction of the nearest emergency phone. At 70mph, the stopping distance given by the Highway code is 315ft or 96m - or approximately the distance between these posts! (That stopping distance is years old and car brakes have improved much since then; however, when I did my PCV [coach] test, they were the stopping distances for the fully laden coach! - up to 23 tonnes for the coaches I've driven.)
However, the highway code suggests that a 2 second gap is sufficient for fast roads as the probability of coming across a static object is much less and also, your braking can overlap with the vehicle in front: the highway code suggests that a distance (in ft) equivalent to the speed of the vehicle (in mph) will be passed before braking is applied (the "thinking distance"). If you're travelling at the same speed as the vehicle in front and have a 2 second gap (the "thinking time" is less than one second), you'll have moved closer to the preceding vehicle, but your braking will still start at a place further back on the road, assuming you start to reach when you see their brake lights (the shock way can bee seen moving back up the traffic flow by the brake lights coming on) - even at 2 seconds to think, you'll start braking at approx the same place on the road.
The problems occur when not enough room is left. That is when over reacting and harsh braking occurs, ieeg if you are past the point where they started to brake.
If by being ripped-off, you mean not being offered the correct odds, then all casinos are ripping you off. Take, for example, Roulette: the odds are worked out correctly if there were no zeros on the wheel; eg on a single number there the odds are 37 to 1 that the ball won't land on your number (36 numbers + 2 zeros), but you only get paid at 35 to 1. Your expectation at roulette is -5 5/19%, ie for every $1 you bet, in the long run you can expect to receive approx $0.95 back.
If by being ripped-off you mean being cheated, then yes. (Things like gaffed roulette wheels whereby the ball can be directed to avoid numbers, etc).
My advice if you must gamble in a casino: play Blackjack - the odds are constantly changing as each card is dealt and at times actually favour the player. (There is still a possibility of cheating with the dealing of the cards.)
I must admit to not having played many recent games, but I do remember playing games of both styles. Level games had the advantage in that there was a definite break when the game could be stopped (and saved) and restarted easily at a later time, but with non-levelled games, restarting a game after a break would leave me disorientated for a few, sometimes vital, moments whilst I got back into where I was in the game. (At least with the books, I could easily refresh my memory by quickly skimming over the previous paragraph or two.)
But is that available at the point of sale where the sales contract is made?
I have often made spur of the moment purchases with no prior knowledge of the publisher and with no internet access available; am I expected to visit every software publisher's website to check out the EULA of every piece of software on the offchance that I may see it offered for "sale" and decide the "buy" it?
I was told when recently "purchasing" some software that it was only licenced (and would refuse its return if the package was opened). However, there was no clear licence available on the package (only readable by opening said package in which case the shop would refuse a refund - I don't know how legal that would be), nor at the till to explicitly tell me what the licence was.
Incidently, on installing one of the pieces of software it came up with a message that the software was only licenced, not bought; it then came up with a message "thank you for buying this software". (Not buying a licence to use the software.) If the software (installer) publisher can't decide whether it is bought or not and tells us two conflicting statments regarding that, how can the rest of us know?
Well, there is a sort of prior art in [the good ol' ASCII graphic'd *nix] Larn: after collecting gold and treasure on the way to getting the specific potion, depositing some of said gold in the bank, etc, once you had found the potion and completed game you'd get emails from the game requesting you pay your taxes! (Obviously in games funds.)
So re-instate the demand for a working model that the Patent Office used to require. If "people" want software patents, then the "device" is software and so a software implementation (including source code) should be provided as a working model which would then be available for anyone querying the patent to view.
The "storage" for software patent working models won't be the problem that the storage of a [physical] working model requires (which caused the cessation of said need) as I'm sure a modern Hard disk could store many software patent source codes.
Creating working models with software is probably much easier than with physical inventions, therefore I can see no reason not to demand a working implementation.
Isn't it "Advanced Access-Control System"
Maybe, but whilst awaiting tral, a person is encarcerated in jail - with their freedoms of movement, action, normal everyday business, etc curtailed, unless bail is paid; whilst corporatons are awaiting trial are they incarcerated, unable to do normal everyday business, unless they post bail - do they even post bail?
In the UK, at least, it would appear to be in breach of Section 1 of the Computer Misuse Act 1990:
1 -- (1) A person is guilty of an offence if--
(a)he causes a computer to perform any function with intent to secure access to any program or data held in any computer;
(b)the access he intends to secure is unauthorised; and
(c)he knows at the time he causes the computer to perform the function that that is the case.
The data sent home is noted by (a). As the user has expressly not agreed to the WGA EULA, unauthorised access is noted by (b) and (c) - in particular (c) as there was no agreemnt to the EULA; assuming of course that the data sent home is that that would be sent home IFF the EULA had been agreed and WGA installed.
As an aside, the Sony rootkit that installed something even when the EULA or whatever was decined was probably in breach of Section 3 of the same Act - doing "...any act which causes an unauthorised modification of the contents of any computer..." - those discs weren't sold in the UK?
The question is who is the responsible entity for a company: they have programmers that have written the code that does the unauthorised access (are they responsible), or is it their managers (who defined the specs) or the company as a whole (the directors)?
The only licence you have to use someone's code is the licence they give you. If you don't understand their licence, then you should at least look at copyright law. That, I'm sure, is rather explicit that you can't just take stuff, eg open-source program, someone has written and use it in any way you please, eg in a closed-source program. If you don't fully understand the GPL, then contact the author as to his/her requirements for use of their code; if you can't make contact then assume Copyright Law - the GPL gives extra rights that Copyright Law doesn't and all you would lose is those extra rights.
I'm sure that the DOJ investigation into MS's practices and monopoly position came up with a breakup solution (separating the OS and applications divisions so that, for example, MS applications would not have the inside information of undocmented APIs, but would be forced to use the publically documented ones and so compete on merit), but it never happened, etc.
Alternatively, arrive 30 minutes after the advertised start of the film - last time I went to the cinema, due to delays at the pizza place we went for food (sic) before seeing the film, that's just what we did: we arrived just as the film we wanted to see was starting (we had purchased our reserved seats (as all the seats in the cinema were) before going for our food) and missed all the ads, trailers and anti-copyright infringement notice.
What really annoys me is the 30 second unskippable ad expounding (erroneously) piracy as theft ("...you wouldn't steal a movie? downloading is stealing...") on a DVD I legally purchased is actually stealing from me: my time (the 30 seconds of the ad - they haven't paid me for their advertising) PLUS the electricity required to power my DVD player during that period, plus (though not absolutely necessary as I could turn them off - which then makes the ad useless!) my TV & surround sound system. So far they have stolen around 15 minutes of my time and electricity.
I presume this is this is a possible story being mentioned, but this one mentions something more likely (Ms Austin's gnome). I hope they're true.
So maybe he'll be sentenced to 101 concurrent 1 year sentences totalling 1 year in jail all together.
As long as he commited those 101 offences concurrently, at exactly the same time. The sentences should overlap timewise similarly to the orignal offences: commit 1000 offences, get 1000 years for them (1 each); commit 100 at a time, so take 100 sentences together to give 10 years to execute the punishment. Simple really. Now how many people were spammed with how many messages each over what period of time? Based on the amount of spam I have received this year so far, and the amount of repeat (different timed) spam, that makes...100,000+ years at a guess...at 101 years he's getting off lightly, and that's for the spamming only - not taking into account the other offences.
The colon prefix to commands in vi is actually accessing ex commands (FWIU).
The one thing I miss in vim is the inability to use term=dumb that vi could - vi would display only the current line in the buffer and normal screen movement commands would be sensibly mapped[1]; the only cursor control vi required for term=dumb was ^M (carriage return = goto start of line, adding ability to do ^H (backspace) improved speed of use as going left 1 char used that as opposed to ^M{line upto char}.
[1]I've used vi over a 300 baud modem link on a glass yty (=dumb terminal that only understood cursor controls ^M & ^H) and it was most usable. [One of the commands was mapped to display the context of the current line by showing the previous 10 lines, the current line and the following 10 lines.]
When I studied traffic flow as part of my Maths degree 20 years ago, traffic flow was modelled using fluid dynamics.
You're forgetting that the capacity of the road is usually based on how many vehicles can fit along it, ie vehicles/lane-mile - and as speed reduces, there is need for less gap between vehicles and so more vehicles can fit per lane-mile; the flow is the number of vehicles that pass by in a given time. Congestion occurs when there is not enough road space for the vehicles.
Braking distances given in tables are based on square of speed. As speed reduces, so does braking distance. If the stopping distance as given by such tables is left between vehicles, the time between vehicles will also change (eg at 20mph, dist=40ft which is ~1.4secs; at 70mph, dist=315ft, which is ~3.1secs). At just below 40mph (38 2/3mph) the braking distance given by the table actually takes 2 seconds. So above about 40mph, the 2 second separation rule is giving less than the stopping distance between vehicles, but those speeds are [usually] reserved for "fast" roads where something isn't really expected to "jump out" and cause the preceding vehicle to stop instantly, so the thinking and braking distance an overlap the vehice in front - in the time it takes you to react, the preceding vehicle will [usually] have moved forward [relatively] quite a way.
So how does reducing the speed improve the capacity, and flow?
The maximum capacity is when there is zero gap between vehicles, ie their speed is zero, but that is the worst case flow (also zero).
So what about 70mph & 60mph? Assuming a car of about 15' length and a separation of 2 seconds:
70mph: 2 secs ~=205', car-space = 205+15 = 220, giving 24 cars/lane-mile. Thus we have 70 * 24 = 1680 cars/hour.
60mph: 2 secs =176', car-space = 176+15 ~= 190, giving ~28 cars/lane-mile. Thus we have 60 * 28 = 1680 (actually ~1667) cars/hour
So although the speed has been reduced by 15%, the flow has only been reduced by barely 1%; but the capacity of each lane-mile has increased by about 16% - an extra 4 cars are able to use each mile of each lane of the road.
If the stopping distance is left between vehicles: at 70mph, the cs is 315+15=330', allowing 16 c/lm, or 1,120 cars/hour; at 60mph, the cs is 240+15=255', allowing ~21 c/lm, or 1,242 cars/hour. So by reducing the speed by 15%, in this case the capacity has increased by about 29% (5 extra cars/lane-mile) and the flow has increased by almost 11%!
If you do the maths, you'll find the optimum speed for the max flow when the stopping distance is left occurs when speed = sqrt(20 * mean_length_of_vehicle)! So the more longer vehicles there are, the faster the speed for optimum flow - so be grateful for all the coaches and arctics.
From the UK Highway Code which uses the age old formula:
distance = thinking distance + stopping distance = speed + speed^2 / 20
where distance is in feet, speed is in mph.
At 70mph, 2 secs is approx 205ft. According to the UK Highway code, the average car length is 4m, or about 13ft, so leaving 2 secs between cars leads to a front bumper to front bumper distance of 205 + 13 = ~220ft which allows for 5280/220 = 24 cars/lane-mile.
Just remember that the UK has a much smaller area than the US; and our cars are much smaller.
Incidently, when I did my PCV (bus driving) test 12 years ago, these typical stopping distances were the ones I was expected to know for the coach.
Optimum braking is effected when the wheels are just about to lock and a skid is about to start. I don't know about you, but I certainly can't manage that whereas ABS can.
However, in most circumstances, you won't be braking that close to skidding and ABS will actualy have no effect on your braking distance - all it will (usually) do is provide you with control in that you'll be able to steer which would normally lower the point at which a skid would start, and so enable you to still stop safely whilst steering round obstacles. [I think - IANAME: I Am Not A Mechanical Engineer ^_^]
In the UK, 315ft is actally quite easy to roughly visualise on the motorways (to an accuracy of about 13ft, or 4m) - 315ft is approx 96 metres. Along the side of the motorway are numbered marker posts (that point to the nearest emergency telephone): they are 100m apart. 315ft is slightly less than this, so use the marker posts (as an approx over estimate).