The study of British and Irish roads - their construction, numbering, history, mapping, past and future official roads proposals and general roads musings. There is a separate forum for Street Furniture (traffic lights, street lights, road signs etc). Registered users get access to other forums including discussions about other forms of transport, driving, fantasy roads and wishlists, and roads quizzes.
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- A303Chris
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Post by A303Chris » Wed Jan 19, 2011 10:36
I wonder if any one here can help me as i am stumped. I have had a query from another department which asked me what traffic flows consistute high, medium and low traffic flows. My response is below and I say that it is all relative to the type of road and from my 24 years in the profession and looking at various documents i can not find any figures. Does anyone know if any exist ? I know the DMRB states the capacity flows for different road types , but this is different to breaking the flows up. Thanks for any help Chris My short response was
"There is no actual description on what high, medium and low traffic flows are as the flows are all relative to the type of road. For example 20,000 vehicles would be a low flow on a motorway, but a very high flow on an “B” road in the country. DfT guidance is you determine a road on the local characteristics."
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- Haydn1971
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Post by Haydn1971 » Wed Jan 19, 2011 11:58
Words are very subjective, the trouble with making reference to a current design document is that most roads were not designed using it. My initial view without know any further background would be that traffic is at a percentage of the road capacity outlined in TA 79/99, which has a degree of subjectivity in terms of a road being a UAP1-4 type. From experience we all know that a road at DMRB capacity isn't at a standstill, but the performance starts to drop at a percentage over that capacity, I'd put that at about 20% over, but some of the transport bods might have a more accurate idea and of course, other feature like hills will influence the figures in TA 79/99
From this you could go further in establishing a two tier approach highlighting roads that are over capacity just at peak or for periods outside of peak and roads that are in the near capacity range, for example 90-120% of that suggested by TA 79/99
- cb a1
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Post by cb a1 » Wed Jan 19, 2011 12:46
It's not dissimilar to being asked how bad the congestion is on a road. We all know what congestion is, but it's a PITA to define. I would guess the answer will depend on who's asking the question and for what purpose. For example, air quality and noise are predominantly dependant upon the number of vehicles with relatively minor modifiers for speed and acceleration. Conversely other queries might really be after V/C ratios.
To the best of my knowledge, there are no defined parameters for any of the above in terms of ranking them as High, Medium and Low.
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- wrinkly
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Post by wrinkly » Wed Jan 19, 2011 15:00
Is there any possibility that the person asking the question really intended to ask about low, medium and high projections for future traffic growth? Or had read something about those and misunderstood it?
- A303Chris
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Post by A303Chris » Wed Jan 19, 2011 15:55
Thanks for your help, it was i expected. Wrinkley the request was from our park departments who want to increase sponsorship of roundabouts / verges etc and they want to classify sites in to low , medium and high traffic flows, thereby charging more for busier roads. Trouble was while someone came up with this idea they had no idea what was a low, medium or high flow and just thought that transport would know the figures
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- RichardA35
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Post by RichardA35 » Wed Jan 19, 2011 16:03
A303Chris wrote:Thanks for your help, it was i expected. Wrinkley the request was from our park departments who want to increase sponsorship of roundabouts / verges etc and they want to classify sites in to low , medium and high traffic flows, thereby charging more for busier roads. Trouble was while someone came up with this idea they had no idea what was a low, medium or high flow and just thought that transport would know the figures
Surely you should classify by the number of pairs of eyes and the duration of seeing the sponsorship boards - more money for those on a bus route and even more for those on routes subject to severe congestion.....
- WHBM
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Post by WHBM » Wed Jan 19, 2011 17:05
Can you not tell the Parks team that we do not do a simplistic Low/Medium/High classification, but assess flows in terms of vehicles per hour or per day - and give them those.
Near here the Honda sponsored roundabout (M4 J5) http://maps.google.com/?ie=UTF8&ll=51.4 ... 6&t=h&z=19 , outside the Honda UK HQ building, is only well known as such because it is signalised and the signage is in front of you while waiting at the light. There's another one nearby which I can't recall the sponsor of because it's not signalised so I'm always looking right, rather than musing at the landscaping, while waiting to join. Nothing to do with traffic flow.
Ask the potential sponsor what it's worth to tweak the signal timings so people spend more time at the stopline
- nirs
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Post by nirs » Thu Jan 20, 2011 08:36
cb a1 wrote:We all know what congestion is, but it's a PITA to define.
I often think of it as the difference between how long a journey takes in reality compared to the length of time it would take if you were able to drive legally at your desired speed between junctions, not have to queue to get onto roundabouts and get through every set of lights in a single sequence.
- A303Chris
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Post by A303Chris » Thu Jan 20, 2011 09:29
Haydn1971 wrote:That's a simple one to answer then, Primary A roads are busy, A Roads are less busy, B/C Roads are quietest and no one will pay for roundabout sponsorship in the middle of a housing estate !
Haydn, in some of our housing estates you would not want to put a sign as it would not last for more than 5 minutes. Seriously I have gone down this route as for DC purposes we have have main distributor roads with greater than 10,000 vehicles per day, local distributor roads with less than 10,000 vehicles and other roads less than 5,000 vehicles per day. I have passed this to parks after discussing further and they are happy with this.
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- Mark Hewitt
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Post by Mark Hewitt » Thu Jan 20, 2011 10:05
In that case it would be pretty easy, sample traffic flows at a cross section of possible advert sites and then divide it into three completely arbitrary segments, and voila!
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- cb a1
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Post by cb a1 » Thu Jan 20, 2011 12:58
nirs wrote:cb a1 wrote:We all know what congestion is, but it's a PITA to define.
I often think of it as the difference between how long a journey takes in reality compared to the length of time it would take if you were able to drive legally at your desired speed between junctions, not have to queue to get onto roundabouts and get through every set of lights in a single sequence.
That's generally the quantitative method used but conceptually it doesn't meet what many lay-people think of as congestion.
Say you're the only car around but a pedestrian activates a ped crossing which holds you up for 10 seconds. It's a delay, but to call it congestion ...
Education makes the wise slightly wiser, but it makes the fool vastly more dangerous. N. Taleb
We tend to demand impossible standards of proof from our opponents but accept any old rubbish to support our beliefs.
The human paradox that is common sense
The Backfire Effect