Safe Speed Forums

The government have launched a consultation on proposed changes to the Highway Code. See:

http://www.dsa.gov.uk/content.asp?id=13014

A few points that struck me on a skim-read:

• new rules 151 and 152 specifically prohibit the use of mini-motorbikes or quad bikes on the road
• topically, rule 142 now mentions smoking as a potential distraction when driving
• metric equivalents of speed limits are now given
• Rule 216 now says: "Large vehicles can block your view. Your ability to see and to plan ahead will be improved if you pull back to increase your separation distance. Be patient, as larger vehicles are subject to lower speed limits than cars and motorcycles. Many large vehicles may be fitted with speed limiting devices which will restrict speed to 56 mph (90 km/h) even on a motorway."

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

A revision of stopping distances would be useful, as those quoted in even the latest versions of the code remain those of a Morris Minor, complete with drum brakes, two-inch-wide crossply tyres, no servo, and chassis/steering/suspension last seen trying to keep up with Ben Hur.

It's a long time since I did the subject and I would have to dig out some old manuals to look up the formulas, but, some years ago, when I back calculated the stopping distances in the Highway Code they each came out to an Acceleration factor of 0.7, which is a typical figure for a surface in a good state of repair.

The Acceleration factor, in a non-scientific explanation, is the 'stickyness' at the contact point between the road surface and a tyre and is expresed as a proportion of the force of gravity. Gravity being expressed as 1, and equates to 32.2 metres per second per second.

Regardless of the type of brakes, tyres, suspension, etc, stopping distances are, and always will be, determined by the characteristics of the interface between tyre and road. Or, as Scottie says, "You canna change the laws of physics".



This is both factually and legally inaccurate. The requirement of a speed limiting device (under EU Regs) is for it to be set to 85kph + or - 5%, which equates to between 52 and 56 mph.

Most are set to 56.

Some are set to 54.

There is an upcoming trend to set them to 52 mph as there can be a significant saving in insurance premiums.

One change that I would like to see, can't remember the rule number off hand, is
Give signals is they would warn or inform other road users....
to which I would like to see added,
........or to eliminate uncertainty.

The argument for this? One illustration would be a 'Y' type of junction, approaching from the bottom, where the major route follows on to the right, but where there is significant local traffic that takes the left fork. Motorist is waiting to emerge from the left fork turning right, and is becoming frustrated by the number of 'numpties' that have turned into his road without signalling.

Driver following the major route, with no other turnings, service roads, accesses, etc, signals right to the effect that he will be passing across the front of the waiting vehicle.

Uncertainty eliminated.

I'm sure there are many more examples.

and you too as you pull in front of the numpty who forgot to cancel his left indicator 5 miles back.

..

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Q. Are you a stupid fascist with limited reading skills or are you just a retard?

Grumps- are you saying that a modern car can't stop any quicker than a Morris Minor? Sorry, don't agree.

A bike example:
Kawasaki Z250A and Z250B, same bikes apart from paint job, exhausts and brakes- the A had discs, the B drums, and the disc-braked model would ALWAYS pull down faster than the drum model.
I agree that there is a point at which any tyre can break traction, but there's a whole load of difference in how quickly various vehicles get you to that point, and the tyres themselves (coupled with the road surface etc) determine where that point lies.

And FJSRider has it pretty well right regarding the g figures (9.86 metres per second per second).

There's an article about the Highway Code consultation in today's Sunday Times:

http://www.timesonline.co.uk/article/0, ... 65,00.html


I have to say having had a reasonably thorough read of it, there's little to strongly object to (although a number of missed opportunities) but the tone is becoming increasingly patronising.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

Sorry grumps, but car tyres haven't had an acceleration factor (adhesion coefficient) of 0.7g for a very, very long time.

Modern tyres are between 1.1g and 1.7g, with racing slicks going up to nearer 3.0g (when the highway code stopping distances were devised, tyre maufacures stated it impossible to acheive 1.0g, never mind higher figures!)

The "stickiness" of the tyre also has very little effect under harsh braking (unless you re going sideways) - it is the overall effiency of the braking system to transfer energy into heat via the discs that counts. Infact, in a modern car if you brake as hard as possible in a straight line, you will never reach the grip limits of the tyres as the ABS will prevent you from doing so. This is to keep the discs turning and energy transfer at its peak - if the wheel was to lock then its all down to the tyres and you are in big trouble.

Suspension is also a major factor, as it will prevent all the braking force shifting to the front of the car and help spread it more evenly between all wheels (EBD is a major help in this, so a big tick on the options sheet for that one!)

Thinking distances remain the same, but all modern cars can stop well short of the highway code distances for the given speeds (an Audi RS4 can stop from 70mph in the highway code distance for 30mph!)

That's what I said.

Did I mention tyres in this context?

I'm fairly happy with it, and am pleased to see no increase in emphasis on speed limits. I do find the following a bit pointless though:

Oh, something else that comes to mind: http://www.collisionreporting.gov.uk/ is mentioned in the list of useful websites, but at present it is surely of no use except maybe to the police - does this mean they have good plans for it, perhaps similar to those that have been in the Safe Speed manifesto for eons?

It would be nice if EVERY road user was made to read it!

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

Signalling right when following the road ahead could me misunderstood too. The problem would be solved very simply if EVERYONE turning left indicated. That way the traffic waiting to pull out would know that unless someone was signalling they were going straight on.

Personally I would like to see a small endorsement (1 point) and a fine for incorrect or lack of use of signals. There's no excuse. If you don't know when and how to signal properly then you need to read the highway code. And don't even get me started on people not understanding arm signals!



Possibly random questions on it every time someone is stopped by the BiB. Oh yeah, sorry, there aren't any are there?

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Science won over religion when they started installing lightning rods on churches.

I would have agreed with you until I did the sample driving test questions on the DVLA website the other day and got the question on tramway markings wrong

My excuse is that there are no trams anywhere near me!