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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#11
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In message om, Tudor
Hughes writes On Feb 8, 11:25 am, Graham P Davis wrote: Dave Liquorice wrote: It may well be the parents first significant snow fall let alone the kids. This is half the trouble with the roads, no one under the age of about 35 will have had the chance to drive on snow and it's not taught as part of the test. I remember people saying much the same thing forty years ago. Snow and ice was a lot more common then, but the vast majority of drivers hadn't a clue how to drive in slippery conditions. We agreed that the driving instruction - and probably the test - should include experience on a skid pan. -- Graham P Davis Bracknell, Berks., UK Send e-mails to "newsman" as mails to "newsboy" are ignored. Ability to control or avoid a skid may be of use to racing drivers but is pretty pointless for the average motorist. The reason the roads jam up in snow is due mostly to the fact that in many places they are at nearly full capacity anyway. The traffic just about keeps going under normal conditions but anything that slows the flow will soon cause long delays. For example a steep hill may become unusable due to lack of adhesion and the traffic has to be diverted, adding to the congestion. No amount of skill will increase the coefficient of friction between tyres and ice, snow or slush. Ability to drive in snow may have enabled you to get through when there was hardly a car on the road (say, 1930's) but nowadays the problems are entirely different. Careful use of the throttle and clutch with the car in 3rd gear and keeping the revs down will often get you going/keep you going on a bit of a hill whereas high revs in first gear will guarantee that you'll come to a stop. There were plenty of the latter unsuccessfully trying to get up our road this morning with much revving of engines and sideslipping into the gutter. Those who approached the hill in a high gear with low revs got up without any trouble. Norman. (delete "thisbit" twice to e-mail) -- Norman Lynagh Weather Consultancy Chalfont St Giles 85m a.s.l. England |
#12
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Felly sgrifennodd Tudor Hughes :
The traffic just about keeps going under normal conditions but anything that slows the flow will soon cause long delays. Well, anything that increases the stopping distances can cause delays, as motorists leave larger gaps between the cars. Merely slowing the flow can have a positive effect, up to a point, as seen from the variable speed limits around parts of the M25 and M42. Adrian -- Adrian Shaw ais@ Adran Cyfrifiadureg, Prifysgol Cymru, aber. Aberystwyth, Ceredigion, Cymru ac. http://users.aber.ac.uk/ais/weather/ uk |
#13
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Tudor Hughes wrote:
Ability to control or avoid a skid may be of use to racing drivers but is pretty pointless for the average motorist. The reason the roads jam up in snow is due mostly to the fact that in many places they are at nearly full capacity anyway. The traffic just about keeps going under normal conditions but anything that slows the flow will soon cause long delays. For example a steep hill may become unusable due to lack of adhesion and the traffic has to be diverted, adding to the congestion. No amount of skill will increase the coefficient of friction between tyres and ice, snow or slush. Ability to drive in snow may have enabled you to get through when there was hardly a car on the road (say, 1930's) but nowadays the problems are entirely different. Not all roads are nose-to-tail traffic, even now. You don't have to be driving fast to get yourself into a skid. Some causes may be driver-related or mechanical, such as having poor tyres. I found this out when I bought a new car that came fitted with Michelin XZX tyres. If I'd known the trouble they'd be I'd have asked them to swap them for something else - anything else - straightaway. They never gave me any confidence that they'd stay on the road. On one occasion, a slightly dewy morning, I lost all grip at the front on a bend at less than 10 mph. I got rid of the tyres when there was still more than 3mm tread left - three times the then legal minimum. -- Graham P Davis Bracknell, Berks., UK Send e-mails to "newsman" as mails to "newsboy" are ignored. |
#15
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On Thu, 8 Feb 2007 09:44:47 -0600, Harold Brooks wrote:
What did the weather situation end up being like? Two reports in "[WR] Dudley, West Midlands" the first at 1144 gives 3-4 cms depth with snow fall starting about 0430. The second at 1548 gives 10cm with continual snow. So that's about 1.5cm/hr. This is day time, a bit of rock salt, plough down and the traffic will keep the roads clear without any trouble. 10cm (4") is hardly a heavy snow fall either. I know that, in our recent ice storm, we were very happy when decisions to close were made the afternoon before because it allowed us to make plans much easier than if we had to wait until the morning. Surely the forecast would tell you that the sensible thing to do is make plans then not wait until the morning to make them? All you have to do in the morning is impliment them, or not. -- Cheers Dave. pam is missing e-mail |
#16
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On 8 Feb 2007 06:21:34 -0800, Tudor Hughes wrote:
For example a steep hill may become unusable due to lack of adhesion and the traffic has to be diverted, adding to the congestion. No amount of skill will increase the coefficient of friction between tyres and ice, snow or slush. True but knowledge and technique can ensure you make maximum use of what traction is available. Hills become snarled up for ascending traffic because people just floor the accelerator making the wheels spin. Descending because they use the brakes, wheels lock and they slide out of control into the equally out of control stuff trying to get up. Gently gently in a high gear is the way to make progress, all but the very gentlest of braking should be avoided, use the gears and engine to slow down. Of course this means you have to look a long way ahead and read the road properly. Just as Mr Lynagh illustrated I've done the same thing on a snow covered hill (Westbury Road, Bristol, up onto the downs, early 80's I think) cars with spinning wheels sliding about all over the place trying to get up. Me, just have it in third about 20mph it simply chugs up and past them all, no fuss no drama. Perhaps part of the test ought to be to drive a car that has no or minimal brakes? -- Cheers Dave. pam is missing e-mail |
#17
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In article om,
says... On Thu, 8 Feb 2007 09:44:47 -0600, Harold Brooks wrote: What did the weather situation end up being like? Two reports in "[WR] Dudley, West Midlands" the first at 1144 gives 3-4 cms depth with snow fall starting about 0430. The second at 1548 gives 10cm with continual snow. So that's about 1.5cm/hr. This is day time, a bit of rock salt, plough down and the traffic will keep the roads clear without any trouble. 10cm (4") is hardly a heavy snow fall either. I know that, in our recent ice storm, we were very happy when decisions to close were made the afternoon before because it allowed us to make plans much easier than if we had to wait until the morning. Surely the forecast would tell you that the sensible thing to do is make plans then not wait until the morning to make them? All you have to do in the morning is impliment them, or not. It depends on what the plans are for. I know that I was very happy to be able to have children not set alarms to get up in the morning and let them sleep in. Having my teenage daughter asleep rather than awake and grouchy was worth something.:-) In one case of a group that was going to have about 250 people gathering on a Friday evening to play basketball, because of volunteer staffing schedules, it was much each easier to communicate closure on Thursday afternoon than to wait until Friday. The message got out to 95+% of the people that afternoon. There are costs associated with waiting until close to events to cancel that aren't there if you cancel early. In our local district, school bus drivers don't have to get up early enough to make their way from their homes to get their busses if they know the evening before. It's a fairly classic decision problem: given the costs of missed events and false alarms, where do you set your threshold for cancelling an event? Costs of missed events tend to go up as you approach event time. (Did the word get out to everyone? Did people who need extra time under normal circumstances begin preparations needlessly?) It's not always an easy call. In Norman, we've had five days of missed school this year (I think that's right), which is as many as we've had in the past decade total. Four were called off the afternoon before. One of those shouldn't have been, but three were great calls. I have no idea what I would have done in the Dudley situation, given that I'm not familiar with the local constraints, but I, for one, wish such decisions were made earlier more often than they are. -- Harold Brooks |
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