£300m traffic jam busting scheme made journeys longer, Highways England admits

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jackal
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£300m traffic jam busting scheme made journeys longer, Highways England admits

Post by jackal »

Pinch point schemes increased journey times on the whole, with shorter peak journey times outweighed by longer offpeak journey times. Traffic lights were the main culprits.

https://www.independent.co.uk/news/uk/h ... 58576.html
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Ruperts Trooper
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Ruperts Trooper »

jackal wrote: Sun Apr 07, 2019 14:52 Pinch point schemes increased journey times on the whole, with shorter peak journey times outweighed by longer offpeak journey times. Traffic lights were the main culprits.

https://www.independent.co.uk/news/uk/h ... 58576.html
To my view as a driver, traffic lights are the direct opposite of "smart" - somewhat surprising given the ready availablity of technology and traffic sensors - far too many seem to operate at peak flow timings when virtually no traffic is about
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by WHBM »

I've long found that HE signal setters are some of the more incompetent at phasing. I could do better with my 1970s-era graph paper, pencils, and diagonal green bands.

I also think it's very poor of Highways England to blame the worst cases on "being done by a previous administration, Highways Agency". We all know it's the same organisation just with a name change when Wales/Scotland were devolved.

Someone there seems to have a thing against part time signals as well.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by trickstat »

Ruperts Trooper wrote: Sun Apr 07, 2019 15:46
jackal wrote: Sun Apr 07, 2019 14:52 Pinch point schemes increased journey times on the whole, with shorter peak journey times outweighed by longer offpeak journey times. Traffic lights were the main culprits.

https://www.independent.co.uk/news/uk/h ... 58576.html
To my view as a driver, traffic lights are the direct opposite of "smart" - somewhat surprising given the ready availablity of technology and traffic sensors - far too many seem to operate at peak flow timings when virtually no traffic is about
And then you have full-time traffic lights at locations where, at most, you would only want peak time control, such as here -

https://www.google.co.uk/maps/@51.88775 ... 312!8i6656

This is at Junction 7 of the A1(M) which is Stevenage south. Here the only movement to give way to is that from the southbound carrigeway into Knebworth Park and a Novotel hotel. Other than when there is one of the occasional events held in the Park such as a concert, car show or antique fair at weekends this is a movement that is very rare but the lights mean that you will usually have to stop even in the middle of the night. In contrast, Junction 8 has only part-time signals on the roundabout despite there being a much greater variety of movements with it being on the main route between Stevenage and Hitchin plus a couple of accesses to and from villages.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Truvelo »

There are numerous locations where lights should be part time. M5 J2 is another. The main problem during quiet times is lights getting stuck on red due to a lack of traffic on the opposing phase. The system will wait for an inordinate amount of time for a vehicle to trigger the lights in your favour. Until that time you'll be stuck at red unless you decide to proceed regardless which is a common sight at J2 in the early hours.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by WHBM »

I see an HE justification is that the signals have reduced accidents, the implication being this has occurred actually at the signal location. However a principal site of serious accidents is not actually at the signal but back on the main carriageway when exiting traffic on the exit ramp backs up all the way down to the main carriageway lanes.

Adequate smart signal setting can minimise all the described issues, but is more expensive than controllers which do not have the "smartness". I do wonder if the beancounters intervene and make the engineers go with the cheapest supplier quote, which will of course be for the one with the least functionality.

It does seem that over time signal setting is being moved away from demand activation to fixed cycle, the opposite of what is available commercially on the market, despite the cost of signal kit seeming to have risen well in advance of inflation. My hunch is the old skill set to configure them is being lost, and they just get installed and run with the suppliers' basic default.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by James »

It's a shame that part time lights are not considered and used much more often. It's a badly kept secret that a lot of junctions can cope quite well without lights outside of peak periods.

At these junctions with trunk/principal roads and limited/no pedestrians, the default should be for part time lights. I see very few situations where lights should be needed in the middle of the night.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by djw1981 »

Is it possible that whilst of longer duration, that journey time is more predictable and road systems better capable of dealing with current traffic levels, ie sharing the delays due to congestion more evenly?
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by lefthandedspanner »

Truvelo wrote: Sun Apr 07, 2019 16:30 There are numerous locations where lights should be part time. M5 J2 is another. The main problem during quiet times is lights getting stuck on red due to a lack of traffic on the opposing phase. The system will wait for an inordinate amount of time for a vehicle to trigger the lights in your favour. Until that time you'll be stuck at red unless you decide to proceed regardless which is a common sight at J2 in the early hours.
See also the exit slips at M1 J41, made worse by the fact that bikes are too small to trigger the lights there, unless they're absolutely massive.
Several times I've been stuck there late at night on a 600 cc bike, and the lights only changed when two or three other vehicles came down the slip.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by fras »

The junction of the A5 and A49 in Shrewsbury, Shropshire (£2.5m)
Yes, a complete failure. When is it going to sink-in that with the traffic levels we have, only some serious infrastructure construction will alleviate congestion.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by James »

fras wrote: Sun Apr 07, 2019 17:59
The junction of the A5 and A49 in Shrewsbury, Shropshire (£2.5m)
Yes, a complete failure. When is it going to sink-in that with the traffic levels we have, only some serious infrastructure construction will alleviate congestion.
Its been a classic British thing to build nice high capacity roads, then think a roundabout (or other at grade junction) is a great way to interchange traffic between them. CBRD's bad junctions is a testimony to this.

The pinch point schemes unfortunately were a continuation of this i.e. spend the minimum to do some messing about rather than fix the real problems with the strategic road network. Theres been a couple of decent schemes in recent years like the M1-M6-A14 or the A1(M)-M62 junctions done properly, but they are too few and far in between against the backdrop of inadequate junctions on the network.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by lefthandedspanner »

James wrote: Sun Apr 07, 2019 18:16
fras wrote: Sun Apr 07, 2019 17:59
The junction of the A5 and A49 in Shrewsbury, Shropshire (£2.5m)
Yes, a complete failure. When is it going to sink-in that with the traffic levels we have, only some serious infrastructure construction will alleviate congestion.
Its been a classic British thing to build nice high capacity roads, then think a roundabout (or other at grade junction) is a great way to interchange traffic between them. CBRD's bad junctions is a testimony to this.
The Sheffield Parkway is a textbook example of this. It's a high-quality dual carriageway, practically an urban motorway, that slams into a set of traffic lights at both ends. At peak times it takes longer to get through either of the terminal junctions than it does to drive the entire length of the road.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by fras »

HE spokesman: -

"Meanwhile, we are considering a range of options to improve journeys by using traffic signals which respond to traffic flows,"

In other words, bovine stupidity reigns in HE !

At least, here in Crewe we no longer have to suffer the traffic light jungle stop-start at Crewe Green, (a Cheshire CC scheme, not HE or HA), as they have been eliminated. The result is a bit of a raceway, but its definitely now quicker to get into/out of town..
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Bryn666 »

DMRB doesn't really cater for part time signal operation, so you often get 24/7 signals because of the junction geometry.

Another reason to find that document utterly annoying.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Stevie D »

James wrote: Sun Apr 07, 2019 16:57 It's a shame that part time lights are not considered and used much more often. It's a badly kept secret that a lot of junctions can cope quite well without lights outside of peak periods.

At these junctions with trunk/principal roads and limited/no pedestrians, the default should be for part time lights. I see very few situations where lights should be needed in the middle of the night.
Part of the problem there is that a junction layout that is optimised for traffic signals is often sub-optimal for priority control, and vice versa. Low-capacity (1 or 2 lane) roundabouts are generally OK, but on larger roundabouts you tend to need different geometry – and non-roundabout junctions likewise are different, and then you have the difficulty of indicating to traffic on the minor arms that it needs to give way when signals are not in operation.

Another point to bear in mind is that traffic lights aren't always about capacity and flow, but are sometimes about sightlines. At some junctions where the corners are tight and there are lots of large vehicles turning, priority control can lead to problems with vehicles making opposing movements blocking each other. That complicates the junction geometry even further.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by WHBM »

Stevie D wrote: Sun Apr 07, 2019 20:51 Another point to bear in mind is that traffic lights aren't always about capacity and flow, but are sometimes about sightlines. At some junctions where the corners are tight and there are lots of large vehicles turning, priority control can lead to problems with vehicles making opposing movements blocking each other. That complicates the junction geometry even further.
I'm surprised this point is introduced here because firstly I think all the junctions described are roundabouts which do not have blocking opposing flows, and secondly they were I think all designed initially as unsignalled roundabouts to modern standards, and have only had signals installed subsequently.

The key issue is not having a set of signals, but having multiple closely spaced sets around a roundabout, so when one flow gets a green, they cannot use the green time due to blocking back from the set ahead, and the blocking back also thwarts the designed weaving which roundabout flows depend upon.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Berk »

Bryn666 wrote: Sun Apr 07, 2019 20:10 DMRB doesn't really cater for part time signal operation, so you often get 24/7 signals because of the junction geometry.

Another reason to find that document utterly annoying.
Why doesn’t it?? I presume it’s due to the way it anticipates traffic flows occur??
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by Berk »

That isn’t usually the case on trunk roads. They’ve usually been redesigned or realigned to avoid those situations.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by jedikiah »

The actual report appears to be this one.

The euphemism that seems to deployed for 'made things worse' or 'didn't work as expected' or 'had unexpected consequences' is 'outlier'. For example there are four that on early evidence were outliers on safety, the first 2 major: A120 Galleys Corner, A34/M40 Junction 9 (*), A12 Hughes Corner, and A50/A500 Sideway.

(*) this one also increased mean journey time.
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Re: £300m traffic jam busting scheme made journeys longer, Highways England admits

Post by jedikiah »

fras wrote: Sun Apr 07, 2019 17:59
The junction of the A5 and A49 in Shrewsbury, Shropshire (£2.5m)
Yes, a complete failure. When is it going to sink-in that with the traffic levels we have, only some serious infrastructure construction will alleviate congestion.
As Highways England put it: The scheme introduced signals on the roundabout between the A5 and A49. The A5 through movement and A5 east to A49 movement have very high flows, but now these are held back by signals, causing large journey time dis-benefits which far outweighed the benefits the scheme brought to minor flow movements
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