Safe Speed Forums

Only a fool breaks the 2 second rule was a government advert from long ago.

Is the biggest cause of accidents not allowing enough time to react?

Also, a 2 second gap on the motorway was OK back in the days when there were less cars than today. To fit all the cars on the motorway, the gap would have to be reduced, and therefore the speed.

As speed cameras are here to stay, my only gripe is shoddy signposting of current speed. Especially when speeds for a particular type of road are suddenly reduced and not properly signposted.

But what about off-peak times when the traffic lightens, the gaps increase, the danger recedes, but the limits stay rigid and the cameras keep flashing??

PS Your argument is fundamentally flawed anyway as there is no good reason for the 2 second gap not to be maintained regardless of speed or vehicle density. Tailgating is dangerous at any speed!

The two second gap provides time to react - no more and no less. It does not change with speed. It assumes that your braking performance is similar to the vehicle in front, and within a practical range this really is 'close enough'. However in bad weather conditions differential braking performance becomes more of an issue and it's recommended that the two second gap is doubled.

And, btw, speed cameras are NOT here to stay. They kill us and will be scrapped.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

"... and therefore the speed" is a classic error and misunderstanding. Because the slower the speed the longer it takes a vehicle to pass a fixed point, reducing speed reduces capacity. To show this, consider the maths. I'll assume an average vehicle length of fifteen feet and calculate the capacity of a carriageway-lane at fifteen and sixty miles per hour.

• Fifteen mph
  • 15 mph is 22 ft per sec
  • Each vehicle takes it's length divided by the speed it travels to pass a fixed point. So that's 15/22 seconds = 0.68 seconds.
  • The two-second interval is between the rear of one vehicle and the front of the next, so the time interval between the front of one vehicle and the next is 2.68 seconds.
  • Lane capacity per minute is thus 60 / 2.68 = 22.4 vehicles per second.
• Sixty mph
  • 60 mph is 88 ft per sec
  • Each vehicle takes it's length divided by the speed it travels to pass a fixed point. So that's 15/88 seconds = 0.17 seconds.
  • The two-second interval is between the rear of one vehicle and the front of the next, so the time interval between the front of one vehicle and the next is 2.17 seconds.
  • Lane capacity per minute is thus 60 / 2.17 = 27.7 vehicles per second.

So, at 15 mph each lane of carriageway can safely handle 22.4 vehicles per minute while at 60 mph it can handle 27.7.

However, that isn't the end of the story because we've all seen the number of vehicles carried rise when the traffic is slowed down. The reason for this is that reducing the speed to just below that which the slowest vehicle would travel means that everyone is moving at the same speed. Drivers quickly become complacent and the inter-vehicle separation reduces (typically IME to under a second). This delays the onset of breakdown of flow but this is at a price. The reduced vehicle separation means that drivers do not have time to react and, like any system where you delay the onset of breakdown, when breakdown occurs it may be catastrophic. In the case of the road network, this can simply be a standing wave of stationary traffic going against the direction of travel (one of those traffic jams for no obvious reason). However, also likely is the multi-vehicle pile-up.

_________________
Will

The answer to improving flow on busy motorways is to increase vehicle separation not reduce it. Why is the worst congestion at junctions? Very often because traffic bunches up making it more difficult for vehicles leaving and joining the motorway. If everbody left adequate gaps, particularly around junctions, vehiicles would be able to change lanes and exit/enter the main carriageway much more easily, enhancing traffic flow for everybody.

In between junctions, properly spaced traffic will be able to adjust speed simply on the throttle. Braking actions made necessary by too close following distances causes congestion (and crashes) by itself.

Your initial statement is commonly held but sadly misguided, in fact entirely erroneous.

It is drivers crashing into us that kill people, and cameras stop them by putting the worst where they belong - on the bus.

_________________
I stole this .sig

Oh, OF COURSE - that'd be why road deaths are falling faster than before then. Why didn't I think of that?

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Untrue.

If only! In reality it's almost the opposite - the cameras fail to deal with the worst drivers and end up doing little more than lighten Joe/Jo Average's wallet.

_________________
Make everything as simple as possible, but not simpler - Einstein

When learning to drive, I was taught that the speed limit for dual-lane highway is 70 miles per hour. That there's no need for speed signs because dual-lane highways are 70 miles by default.

However, speeds for these roads are being reduced, and then enforced with speed cameras.

For example, the A1 is dual-lane and 70 mph. Then it's 60mph with a 60mph camera, then it's 50mph with a 50 mph camera. I'm not sure the reason for the speed limits (I don't believe the crash rate and other government lies - perhaps an important person lives near by and can't enter/exit the A1 without a vehicle up his rear - make some slip roads!) but I'm sure it catches a lot of people out and makes the government extra "road tax" that doesn't get spent on making the roads safer.

I think that speed signs should be placed every 500 yards, especially if they're going to mess with the default speeds of a particular type of road.

Although I find the idea of a chump tax very appealing (because it would reduce Gordon's desire to raise my tax bill), I actually think cameras work best against men with heavy feet, which is the ideal thing, really.

_________________
I stole this .sig

It is a good distance, but only if it is good dry conditions, if it is wet, the rule changes, and 2 seconds should be doubled.

_________________
Steve

All true of course, but I think Gordon68 was having a pop at the lack of any "safety gap" messages coming from the Ministry of Propaganda (Road Subsection) at the moment. At the moment there's nothing about keeping to two seconds in good conditions, let alone poor conditions, and having once written to the THINK! mob about it there doesn't seem to be any inclination to put the message out again.

ROTFL - yeah, right. Gordon Brown is making so much money from the scams he'll cut other taxes . Oink, oink, flap, flap.

Nope. The ideal thing would be if they worked against people of either sex who drive badly for whatever reason, but for that the scams are as much use as an inflatable dartboard.

_________________
Make everything as simple as possible, but not simpler - Einstein

Yes, have your fun, but you know what they say about death and taxes, and if he has to tax people sort out the health system and fight insurgents, I'd rather he tax speeding chumps, NOT ME!

_________________
I stole this .sig

Isn't there some kind of filter which can automatically flag a "Troll alert" whenever BW uses the words "speed", "limit" or "camera" anywhere in his post?

Cheers
Peter

<sigh> The point is that he isn't doing anything of the kind, so don't go expecting your taxes to go down if they fine more speeders. Gordon's not been getting his money for health, education, T.W.A.T. (ironic how "the war against terror" produces that particular acronym, isn't it ), or anything else from "speeding chumps" as you put it. The pratnerships get almost all of it and leave Gordon with a few mill in change. A lot to you and me, but chicken feed to the exchequer. The £35 billion or so that all drivers contribute in motoring taxes (after taking off the money that is actually spent on roads) is far more valuable, as are the real stealth taxes (more stamp duty and inheritance tax revenue from house prices going up, more revenue by quietly scrapping various tax relief schemes, etc).

Speeding fines and scameras aren't a real stealth tax, just a futile attempt to buy safe roads on the cheap with a lame pound shop policy. You gets what you pays for.

_________________
Make everything as simple as possible, but not simpler - Einstein

My concern is that driving without a safe gap between ones own vehicle and the one ahead is slowly becoming a driving norm. It is certainly endemic on the M54.
When something becomes the norm, no matter how wrong it is, changing it back again is bound to prove difficult, particularly if in this instance, the DfT suddenly proposes coming down hard on 'tailgaters'. People who don't necessarily give much thought to their driving will wonder why they are being punished today for something they've done with impunity for the past umpteen years.
Those 2-second rule ads should be brought back.

This issue does very much concern me. Tailgating is now so endemic that even the police do it (and IME are among the worst offenders). Near me, I regularly see what In Gear calls "panda prezels" following the car in front at less than a second's separation - and I've even seen them tailgating tailgaters. With the police setting such a bad example, it's hardly surprising that Joe Public thinks it's OK.

Unlike the "Speed Kills" plague of half-truths being propaganded about right now in support of the scameratsi, the two second rule can save lives. However, the neglected and overcrowded road network actually needs Joe Public to ignore that rule to avoid the country grinding to a halt. At peak times on most trunk routes, there is just too little carriageway space to carry the traffic that needs to use it.

_________________
Will

Rigpig is right.

Tailgating is a major problem.

But it needs Education and Traffic police to tackle the Drivers.

And on dual+ carriageways we need a raising of the speed limits to allow the traffic to flow according to its need.

Speed cameras do not tackle tailgating.

Strathclyde Police just recently had a campaign encouraging drivers to maintain a safe distance, so at least the message is being put across in some areas.

Having said that, it shouldn't be down to the cops, IMO. The campaign needs to be national and it needs to be sustained and focus on practical, sensible easy to follow advice, of which the 2 second rule is a good example.