Tony Jones Posted November 19, 2007 Share Posted November 19, 2007 I've just been listening to a news item about the Essex bit of the M25. It seems they've introduced an advisory 50 limit which kicks in automatically when sensors detect that traffic is (wait for it) MOVING TOO SLOWLY. And everyone on the radio is calmly discussing this. Is it me or the rest of the world? Tony Link to comment Share on other sites More sharing options...
enodreven Posted November 19, 2007 Share Posted November 19, 2007 Hi, Tony I haven't been listen to the disscussion but they have introduced something similar on the M25 around the M3 /M4 area and it does appear to work, e.g. makes the traffic move more freely, I hope we are talking about similar things ?? What appears to happen in the area i have mentioned is that the overhead gantries show mandatory speed limits when the overall traffic flow slows down and this allows the whole system to make a more even progress rather than the usual racing up to the back of the traffic in front and then braking to slow or even stop, which then takes its time to get moving again, hope that makes some sense, Oh by the way if you do go to the area i am talking about make sure you adhere to the speed shown on the overhead gantry as there are speed camera's mounted on the other side of the gantry in each lane which I have been informed are automatically adjusted to the speed show on the gantry Brian Link to comment Share on other sites More sharing options...
Guest Tracker Posted November 19, 2007 Share Posted November 19, 2007 This system works well on the M42 - no doubt aided by a speed camera on almost EVERY overhead gantry. Link to comment Share on other sites More sharing options...
howie Posted November 19, 2007 Share Posted November 19, 2007 Don,t know if anyone else watched "Secret life of the Motorway" on BBC4 (10 pm) last night, but it made fascinating viewing. Showed how the first motorhomes were built, including the Preston bypass, M1, Pennine Way and Spagetti Juction. Staying with the thread, The first warning signs were powered by car batteries at the base. Any problems, and the police patrols would drive along manually switching them on and off. Didn,t last long however as hard up motorists soon found this a convenient way of replacing their old batteries with new ones. I believe there,s a follow up next Sunday, and possibly a repeat midweek, so try to catch it as it really is worth a look. Link to comment Share on other sites More sharing options...
twooks Posted November 19, 2007 Share Posted November 19, 2007 When they were widening the M6 around Preston there was a 50 limit imposed - and traffic did seem to move much better, when it was lifted you got inside lane - 50 second lane - 58 third lane - 65 fourth lane - 68 with a bottle neck stretching back about 3 miles. so if you were fortunate enough to get in front of this and looked in your rear view mirror it looked like the red arrows in practice formation fortunately I no longer have to go there :D :D :D :D :D :D :D B-) Link to comment Share on other sites More sharing options...
howie Posted November 19, 2007 Share Posted November 19, 2007 What I enjoyed were the stories and recollections of the police and recovery services when first employed on these new motorways. No barriers on the central reservation, and a quick U turn if you missed your exit was par for the course. Thousands of breakdowns as old Morris Minors and Austins etc, deposited the contents of their sumps all over the place, and arguments between the two patrol officers on who should operate the "Ray Guns" for turning on the warning signs after the battery ones were discontinued. Hanging out of the windows to get a clear shot, and then the competition to see who could get the best score for the whole division as well. The police were issued with uprated Jaguars for motorway use. The only way they knew these were special models was when they cut through the headlining to fit the sirens, and there they would invariably find the production workers parting message painted on the inside roof panel. "All coppers are b******s", so nothings changed there then. Link to comment Share on other sites More sharing options...
Tony Jones Posted November 19, 2007 Author Share Posted November 19, 2007 twooks - 2007-11-19 10:59 AM When they were widening the M6 around Preston there was a 50 limit imposed - and traffic did seem to move much better, when it was lifted you got inside lane - 50 second lane - 58 third lane - 65 fourth lane - 68 with a bottle neck stretching back about 3 miles. so if you were fortunate enough to get in front of this and looked in your rear view mirror it looked like the red arrows in practice formation So how is that worse than everyone sticking at 50 Jackie? T x Link to comment Share on other sites More sharing options...
howie Posted November 19, 2007 Share Posted November 19, 2007 Nothing worse than everyone sticking to a set low speed limit on a motorway Tony and all you get is bumper to bumper congestion. Some are in hurry to get where they are going while others just toddle along, but at least this spreads the traffic flow out evenly and in the natural order of things that much easier. Link to comment Share on other sites More sharing options...
GJH Posted November 19, 2007 Share Posted November 19, 2007 howie - 2007-11-19 10:42 AM Don,t know if anyone else watched "Secret life of the Motorway" on BBC4 (10 pm) last night, but it made fascinating viewing. I watched the series when it was first shown a few months ago. For me, the first episode was the best because it showed up how much things have changed over the years but a good series overall. Graham Link to comment Share on other sites More sharing options...
howie Posted November 19, 2007 Share Posted November 19, 2007 Always moaning about whats on the telly Graham, but the BBC can still put out real quality shows when they want to. At least I hope thats what it is, and not just nostalgia. Link to comment Share on other sites More sharing options...
enodreven Posted November 19, 2007 Share Posted November 19, 2007 Tony Jones - 2007-11-19 11:53 AM So how is that worse than everyone sticking at 50 Jackie? T x Hi, Tony I don't know how but it works on the stretch that i have mentioned above, albeit they do vary the speed so its not just 50, which I supose makes all the difference, Thinking about it again, it sounds like it a totally different scheme if they are just going to use a fixed speed [50] then I must agree it dosen't make a lot of sense ?? as the scheme above, as i understand it tries to match the variable speeds to meet the road/traffic conditions and thereby spread the flow ?? Sorry Tony, I should have read the thread properly in the first place ? Brian Brian Link to comment Share on other sites More sharing options...
twooks Posted November 19, 2007 Share Posted November 19, 2007 You didn't have a 3 mile tail back in the outside lane, cars actually used ALL the lanes - quite amazing - wouldn't've believed it if I hadn't been there - no road rage, worked wonders for fuel consumption because it took out the accelerate - brake - accelerate pattern, and it was quicker in peak traffic because you actually did keep moving Don't recommend it - except as fuel saving measure - spent some time on fly drive jollies in the states and 55 mph is mind numbingly boring and thus potentially dangerous - at least on the autobahns you have to concentrate all the time. B-) Link to comment Share on other sites More sharing options...
twooks Posted November 19, 2007 Share Posted November 19, 2007 didn't have the technology then to vary the limit like that - in fact - they botched the lane closed scheme one morning - signs said 3 outside lanes were closed - so everybodies busy moving over - tailbacks about 8 miles long, local radio busy trying to tell everyone that only the inside lane was closed - ie a complete reversal of the signs. only about 2 cars had the radio tuned in - and we took off like bats out of hell down the outside lane - should've seen the filthy looks we got :D :D :D B-) Link to comment Share on other sites More sharing options...
Dave Newell Posted November 19, 2007 Share Posted November 19, 2007 The reason a lower speed limit can improve traffic flow is pretty straight forward and has more to do with human nature than anything. When the national motorway limit is in force but there is a large volume of traffic there is a large number of drivers who will try to exceed the 70 MPH limit and end up driving to close to the car in front. When someone touches the brake pedal there is a wave effect of cars following all hitting the brakes one after the other, this effect increases as it goes further back until there are cars actually coming to a standstill. When a lower limit, say 50 MPH is indicated the majority of drivers will stay close to that limit and not only does the gap between cars increase but because they are travelling slower there is more reaction time available and therefore when one hits the brake pedal the wave does not form to the same extent therby allowing the following traffic to continue at a pretty much unabated speed. Also the very fact that a lower limit is in force makes many drivers more aware of what's going on around them. Finally, many drivers ignore thew 70 MPH maximum limit on the basis that, within about 10 MPH, they will not get stopped by the law. When there is a lower limit in force however they are very aware (usually) that just a couple of MPH over the limit could earn them points from the oveerhead speed cameras. This is, I believe, why a lower speed limit during high traffic flow periods creates a faster overall flow of traffic. D. Link to comment Share on other sites More sharing options...
michele Posted November 19, 2007 Share Posted November 19, 2007 howie, I watched it the first time round i thought it was great series especially seeing how the Motorway services we introduced. Ronni Wood from the Rolling Stones explaining how they all used to meet up for a punch up :D It was good. Link to comment Share on other sites More sharing options...
twooks Posted November 19, 2007 Share Posted November 19, 2007 Dave, sounds about right with what happened then, not so sure about paying more attention tho *-) B-) Link to comment Share on other sites More sharing options...
Tony Jones Posted November 19, 2007 Author Share Posted November 19, 2007 Maybe it IS just me then, but I still can't see how it works. I quote from this morning's report: "When the roadside sensors detect that traffic is moving too slowly, they automatically turn on the advisory "50" speed limit signs." Surely even an advisory limit is pointless in that case, as people are already doing (considerably) less than 50! Unless of course the sensors are set to detect traffic speed of somewhere BETWEEN 50 & 70 - which on the M25 most of us would call "free-flowing," rather than "congestion" or a "traffic jam." It just seems to me that some of our "betters" (?) are obsessed with the idea that the answer to every problem on the roads is to get people to slow down. However, at risk of going off my own thread, I've every sympathy with what Jackie says about the use of lanes. On the Continent, the vast majority of people do what our Highway Code says - they stick to the nearside lane unless they need to move out to overtake. Here, we frequently see long tail-backs of traffic in the offside lane, driving too close to each other and doing no more than 60, when the middle lane is empty. No wonder people pass on the "wrong" side (which incidentally would be perfectly safe if we came to expect it as normal, as in North America; it's the element of surprise that makes it dangerous). Tony Link to comment Share on other sites More sharing options...
malc d Posted November 19, 2007 Share Posted November 19, 2007 Once traffic gets heavy too many people start driving much too close to the car in front. They then brake and a ripple effect is set up, the cars at the back coming to a halt. If everyone drove at a steady speed, maybe at 50 or 60mph and stayed well apart I'm sure there would be a lot less jams. After all, except in exceptional circumstances, why should you ever have to brake on a motorway ? Link to comment Share on other sites More sharing options...
Guest Tracker Posted November 19, 2007 Share Posted November 19, 2007 malc d - 2007-11-19 3:30 PM Once traffic gets heavy too many people start driving much too close to the car in front. They then brake and a ripple effect is set up, the cars at the back coming to a halt. If everyone drove at a steady speed, maybe at 50 or 60mph and stayed well apart I'm sure there would be a lot less jams. After all, except in exceptional circumstances, why should you ever have to brake on a motorway ? Which is entirely the principle of variable speed limits and it does generally work, as long as the speed limit is not too high for the volume of traffic. In as much as you do tend to keep moving it is certainly better than stop start. Link to comment Share on other sites More sharing options...
malc d Posted November 19, 2007 Share Posted November 19, 2007 When someone mentioned the early days of the motorways it reminded me that in 1959, living in Essex, we went for a day out to see the new M1 motorway, as many people did. I remember that for some time people on the motorway would speed up and try to block others entering from the slip roads, who were seen as 'pushing in'. They were treated as people entering from a side road without stopping. Link to comment Share on other sites More sharing options...
enodreven Posted November 19, 2007 Share Posted November 19, 2007 Tracker - 2007-11-19 3:59 PM Which is entirely the principle of variable speed limits and it does generally work, as long as the speed limit is not too high for the volume of traffic. In as much as you do tend to keep moving it is certainly better than stop start. Hi, I think that is the main point the VARIABLE SPEED LIMITS, as i think you get just as many hold-ups on roads with fixed 60mph or 50mph or 40mph. People do exactly the same thing on these roads as they do on motorways. It seems the ability to vary the speed limit to match the conditions works. I don't know that just trying to impose either 70 or 50 will work i think you need the sophistication of the system they employ on the M25 around the M3/M4 corridor to effect control as from what i have been told this can vary the speed limits from one assumes 0mph to 70mph and its suposed to be more or less instantaneous albeit I'm sure that dosen't necessarily work every time ? it still in my opinion has a better chance than just using 2 fixed speeds i.e.70/50 Link to comment Share on other sites More sharing options...
howie Posted November 19, 2007 Share Posted November 19, 2007 Read all the replies Tony and your first assumption was the right one. Laughable. Link to comment Share on other sites More sharing options...
Tony Jones Posted November 19, 2007 Author Share Posted November 19, 2007 Good man Howie. Please take my aspersions on your intelligence (on "Put replies to "Ignore me" here") as friendly legpulling - you're obviously a man of great insight, like myself. Tony Link to comment Share on other sites More sharing options...
Mel B Posted November 19, 2007 Share Posted November 19, 2007 ... separated at birth then .... :D Link to comment Share on other sites More sharing options...
twooks Posted November 19, 2007 Share Posted November 19, 2007 tch what a creep Tony would never thought it of you - or is Howie paying you *-) B-) Link to comment Share on other sites More sharing options...
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