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#51
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#52
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In message , Robert Woolley
writes Speed does kill. You don;t have to be a genius to understand that the faster the speed of a vehicle, the longer it takes to stop. And the faster it hits something else the greater the damage. So as I have two cars, a little one for pottering around in,10+ years old with brakes to match. Also a new car with all round disc brakes and ABS. This car tends to far out brake the old car. Maybe, Both my cars should have different speed limits then. Maybe all cars should have different speed limits, maybe all drivers should have different speed limits depending on their reaction times, maybe etc. etc. Maybe one day, posters will realise that fixed speed limits are too high for some vehicles and too low for others. Maybe the fixed speed posters, when in an ambulance rushing them to hospital for emergency treatment will ask the driver to slow down to the legal limit. Maybe pigs might fly. -- Clive |
#53
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In article m, Martin
Underwood writes Yes, the Magic Roundabout in Swindon is a pain in the bum: it's as if the road designers decided to make it as tortuous as possible - being cynical, I wonder if they decided to make it hazardous so as to keep the traffic speed down: which is silly because the deliberate hazards distract the drivers' attention from the hazards that they should be looking for - other road users! And then there's the roundabout in Hemel Hempstead. This started out as one big 6-way roundabout. It worked fairly well. [...] Actually, if you study both these junctions and other places where ring junctions (to give them the proper name) are installed (e.g. the A13/A130 intersection), you'll see that the junction was trying to handle too much traffic and snarling up. The basic point behind a ring junction is to reduce the average proportion of the roundabout that traffic has to go on, thus increasing the throughput of the junction. Consider a ring junction with 5 exits and assume that all 20 possible flows see equal traffic (this is to aid the explanation; at a real site you would of course take measurements). If you build it as a normal roundabout, the average distance that a car travels around the roundabout is half its circumference [1]. Thus the flow on the roundabout has to be 2.5 times the flow coming in from each road [2]. If you replace it with a ring junction, the average distance a car travels drops to 30% of the circumference [3] and the flow only has to be 1.5 times the incoming flows [4]. Put another way, you gain 66% capacity (though of course you then lose some because of the additional needs to give way, but it's still a net win). [1] 25% of the traffic goes 20% of the circumference, 25% goes 40%, 25% goes 60%, and 25% goes 80%. That works out as an average of 50%. [2] The section from road 4 to road 5 carries all the traffic entering at road 4, 75% of that entering at road 3, 50% of that entering at road 2, and 25% of that entering at road 1. That's 100+75+50+25 = 250% of the traffic entering at any one road. [3] Now 25% goes 20% of the circumference clockwise, 25% goes 40% of the circumference clockwise, 25% goes 20% anticlockwise, and 25% goes 40% anticlockwise. That's an average of 30%. [4] The section from road 4 to road 5 now carries (clockwise) 50% of the traffic from road 4 and 25% of that from road 3, plus (anticlockwise) 50% of that from road 5 and 25% of that from road 1. Total 150%. Moreover, if you are turning right, you go clockwise round each mini roundabout but *anti-clockwise* round the central roundabout, which feels very wrong: Live with it. Any unfamiliar layout feels wrong; what do you think about slip roads on the right instead of the left? -- Clive D.W. Feather, writing for himself | Home: Tel: +44 20 8371 1138 (work) | Web: http://www.davros.org Fax: +44 870 051 9937 | Work: Written on my laptop; please observe the Reply-To address |
#54
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In article , Clive
writes maybe all drivers should have different speed limits depending on their reaction times, maybe etc. etc. The other day some politician was proposing a system whereby your personal speed limit was 90-5N mph, where N is the number of points currently on your licence. -- Clive D.W. Feather, writing for himself | Home: Tel: +44 20 8371 1138 (work) | Web: http://www.davros.org Fax: +44 870 051 9937 | Work: Written on my laptop; please observe the Reply-To address |
#55
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In article , Brian
Blandford writes The whole thing looks like a scam to me. The best way of fooling the cameras - which I know but will not reveal, as I support the concept of congestion charging - requires no power from the battery. The best way of avoiding the congestion charge is incredibly simple and perfectly legal. [I'm reminded for some reason of the US politician who got an incredible reputation of being able to "fix" speeding tickets and thus was always owed favours by the rest of the establishment. His method was really simple: he paid them out of his own money - the political gains were well worth the cost.] -- Clive D.W. Feather, writing for himself | Home: Tel: +44 20 8371 1138 (work) | Web: http://www.davros.org Fax: +44 870 051 9937 | Work: Written on my laptop; please observe the Reply-To address |
#56
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"Clive D. W. Feather" wrote:
The other day some politician was proposing a system whereby your personal speed limit was 90-5N mph, where N is the number of points currently on your licence. Works for me if enforceable. But I suspect it isn't enforceable, even with speed limiters. Colin McKenzie |
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