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[Wittsend]

My car has a miles per gallon display. (it shows mpg in real time and can show an average mpg.)

When driving through our village 20 mph zone (flat road) the fuel consumption goes up 

 

[Simon1959]

20 mph zones really get my goat. My son is currently learning to drive and we have a black box fitted. Driving the car is utterly excruciating. I had no appreciation just how many 20 zones we have. Even main routes in and out of the village where we live have them. It's a joy to just find a 30 zone. What on earth are they thinking? As a previous post says, fine next to schools but carte blanche application everywhere?

What I find is that there is a long queue of traffic behind me getting annoyed because everybody without a black box is driving sensibly at 30 mph.

We also have a plague of dual carriageways limited to 50 mph with the attendant average speed cameras. One section was really badly laid out and dangerous. Did they fix the problem? No. The answer was to apply a silly speed limit. The dangerous section has now been sorted. Has the speed limit returned to 70? Of course not.

And don't get me started on the motorway speed limits. I often drive down the M6 & M5 and they are frankly a joke. I imagine a control room with random buttons being pressed. 70 - 40 - 60 - 50 - 60 - 40. Driving at 40 mph when everyone else is doing 70+ is dangerous.

And finally has anyone noticed how frequent motorways are closed nowadays - It seems to be getting much more frequent. I am struck by the juxtaposition between the Government (any) justifying massive investments on motorways and trains etc because £bn's are lost to the economy because of traffic congestion, and then motorways are closed with massive disruption. Shouldn't the minister of transport stand up and explain why the M6 was closed today!!

Bit of a rant. Apologies. 

[oddjob]

Most of the area around me in West London has been a 20 mph limit for a while.
It was hard at first but once you get used to it it's not bad. I find it quite relaxing and you always pull up behind anyone who overtakes at the next traffic light queue.

[Smokey 11a]

When I was still doing freelance MOT's I collected a car and ran it down to the MOT station. I did 50 in the 50 limit to get the thing nice and warm for the emission test. It passed no problems drove it back all within the speed limit. The owner got a phone call to say 'he's' driven it at excessive speed his black box had told them, he became an Ex customer lol I did some explaining that I had been driving for 50 years and didn't need a computer to watch over my shoulder.

[w3526602]

Hi,

A question that I can't get my mind around...

Take a steady stream of traffic, all driving down a one mile stretch of motorway at a steady speed, with each and every driver leaving a gap appropriate to the Highway Code's specified  gap for that speed.

Question 1. How many vehicles per hour will leave that measured mile, if they all travel at 60mph?

Question 2 How many vehicles per hour will leave that measured mile, if they all travel at 30mph?

I assume we all know that 60mph is  one mile in one minute, so 30mph is one mile in two minutes. Both figures are easy for mental arithmetic. The fly in the ointment is (are?) the braking distances do not increase arithmetically with increases on speed.

I suspect I will not get the answer that we all want. But are the braking distances shown in the Highway Code realistic?

On my teens, I would ride my bicycle behind London Transport's double decker buses, I suspect at speeds up to 40mph, with my front tyre wiping paint off the back of the bus. I would argue that, if the bus braked suddenly, I would crash into it, with a speed differential of almost ZERO mph. But the bigger the gap, the greater the speed differential at time of impact.  Whatever, I'm still here ... although an unlit  street lamp put me in Croydon General Hospital for two months, which might suggest that lamp posts are more dangerous than buses.

The last time I departed London on the M4 (heading for Wales) in the rush hour, the outer lane was indicating 80mph, with about a two metre gap between vehicles. The next lane in was for vehicles like 1960s horse box lorries, and Ladas loaded with half a dozen young men (and all their worldly possessions), apparently from a hot climate. and similar vehicles that seemed to be struggling to maintain 50mph.  I was in the outer lane ... and was staying there, no matter how small the gaps. But that was then ... probably worse now.

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[diffwhine]

Good point.
The published braking distances have not been changed since God was a boy. There is a popular misconception that ABS has reduced braking distances - it has not. It has merely made a vehicle more controllable under harsh braking and by nature of how it works, may actually increase braking distances. (Its also useless when driving on sand but that's another story)

What has improved is brake quality and performance, as has grip on tyres. In all my training sessions, I always clarify the above, and say that these are just indicative. I also take delegates out to a piece of road and ask them to place traffic cones at where they think the supposedly specified stopping distances should be. Its always an eye opener as they invariably get it horribly wrong, so we have little understanding of distance anyway.

Take a standard modern car and try to match published stopping distances and you can normally come in well under what is stated. Try it with a 110 Defender or Toyota Land Cruiser on standard tyres and the figures are quite frightening with or without ABS.

[w3526602]

Hi,

I had to drive from Swansea to Dover, towing a substantial cer transporter trailer behind my S1 (but with an S2 engine)

The M25 was terrifying. To be nice to other drivers, I kept in the nearside lane, with a blur of traffic passing me. Not a problem ... until I came to an exit.

Lane 1 became the slip road OFF, so I needed to be in Lane 2 ... with probably at least a 30mph differential, and no gaps to wriggle into. I did consider slipping off the motor way, round the roundabout. and slip back on again, but decided better the devil you know. I had no idea what I would find on the roundabout.

We have a roundabout, here in Milton Keynes, which I try to avoid. I'm guessing there are at least four, maybe more, lanes on the roundabout, each marked with the road number that it will lead to. Two problems .... I know where I want to be, but not necessarily the road number that I need ... the road markings are obscured by the cars above them, and anyway, nobody is going to change lanes without playing chicken. I no longer have a suitably brutal looking (or battered) vehicle.

I wonder if I can find an overhead  photo of that roundabout?

I once departed London on the A4, and came across what appeared to be a slip road off ... on the right. It appeared to be common practice to blast up on the outside lane, then force your way into the traffic going straight on. On my particular day, there was a policeman, on foot, directing the bad guys back into continuing on the road that they didn't want. I did not envy the policeman his job.

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