Sorry to butt in here, but as I read your exchange I am struck once again by how much people like me, basically strategy, policy, climate guys working in our sector, depend on the knowledge and high competence of our engineering colleagues. Newton had it absolutely right: we are standing on the shoulders of giants.
I think about this in my own work quite often. Thank you from the bottom of my heart.
Eric Britton
Coordinato:r The Five Percent Solution
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Eric Britton. [log in to unmask]
MD. EcoPlan International Association
Founding editor, World Streets
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-----Original Message-----
From: Universities Transport Study Group <[log in to unmask]> On Behalf Of Robert Cochrane
Sent: Thursday, June 13, 2019 3:37 PM
To: [log in to unmask]
Subject: Re: [UTSG] High-volume roads/motorways?
Hi Rob
Think you mean "vehicles per lane per day". And do you mean vehicles or PCUs? In terms of vehicles, the M25 at J15 with eight lanes carries about 210,000 vehicles per day or about 26,000 vehicles per lane per day. Using a twelve hour day to estimate the peak (my guess, but the figures are available), this is a peak of about 2,400 vehicles per hour per lane, which is similar to the UK COBAR maximum recorded hourly values in the 1990s. Speeds are falling in this regime, so the flow is becoming unstable, So 2,500 vehicles per hour per lane is a good absolute maximum and the rest is the daily flow and peaking. US figures are slightly less at about 2,200 but that may be a measurement difference. German Autobahnen in urban areas are similar (how good is your German?) 2,500 gets the flow well into unstable and potential high crash risk territory, but the M25 has a lot of advanced warning signage and also the expected pile ups particularly in poor weather or suddenly changing traffic conditions as any reduction in speed DECREASES the possible traffic flow
Some tunnels and bridges have slightly higher daily figures, as I found in Hong Kong, but these are usually carefully managed pinch points with only four lanes and the jams occur on the approaches where merging is the major issue. Plus different (lower) peak factors for the daily figure. The original cross harbour tunnel carries about 118,000 vehicles per day on four lanes or about 29,500 per lane. Dartford Crossing carries about 160,000 per day on eight lanes, with a higher peak factor as it is not downtown and probably a similar peak figure, although this may also be reduced by the high truck component as it is the London bypass from Dover as well as the London peripheral.
So first, are you looking at managed and tolled pinch points or open untolled road sections as the management problems differ. Second, check whether the figures are vehicles or pcus and one or both directions and the numbers of lanes. If the answer for vehicles per lane per hour free flow is not between 2000 and 2500 something is wrong. 40% to 50% of this for priority traffic light controlled roads.
So check the definition and the peaking and the truck percentage and in the UK, look no further than the bottom left hand corner of the M25 for free flow and Dartford Crossing for managed and tolled pinch point and in Hong Kong, the original cross harbour tunnel. All have good stats. And consider peak and all day separately.
Best wishes
Robert
The upper limit
On 13-Jun-19 01:37 PM, Rob Bain wrote:
> Hi
>
> I'm looking at some very high-volume roads around the world (at or above 30,000 vehicles/lane/hour). As you can imagine (from these volumes) the roads are very intensely used from early morning through to late evening.
>
> Do we have examples of roads in the UK where these sorts of volumes (per lane per hour) can be observed? Or in other countries?
>
> Any thoughts anyone?
>
> Thanks in advance.
>
> Rob
>
> Robert Bain
> RBconsult Ltd
> Investor Support Services
> www.robbain.com<http://www.robbain.com/>
> +44 1732 463314
>
>
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