Tom Siddall is a Principal Engineer at 4way Consulting and a regular Symposium presenter. Working on a wide variety of Traffic Signal projects Tom is in a particularly good position to provide insight into problems and propose interesting solutions. This year he presents a compendium of traffic signal issues:
Goldilocks MOVA linking using MOVA version 8 – Can you get it ‘just right’?
Just what do you get for £500,000? An overview of the DfT/LCRIG funded signals refurbishment project in Slough.
How difficult can it be? When that site you thought was going to be straight-forward gets more and more complicated.
This paper was presented at the JCT traffic signal Symposium 2023 in Nottingham thanks to the support of AGD systems inrix message maker displays PTV group simplify systems smart micro UK and TRL software this is uh hopefully mojo on said heavyweight a fairly gentle start to to the day because when I was trying
To come up with a what idea for a paper I could you know put forward I didn’t have a single sort of wow project that I’d worked on but thinking about it there had been quite a few sites quite a few projects that individually it had sort of interesting elements to them so
I thought I’d try and pull things together taking three projects and three elements from those to hopefully bring together something which is reasonably interesting so the first of those projects is Works we’ve been doing with SNAP Borough Council I’ve worked with them many guyses for many years and this project started several years
Ago where we were asked if we could try and write a lot of the bid documentation for the DFT refurbishment project something unusual for me because whilst I’ll write bids to try and win work in a consultancy to actually win funding in a council is is quite different
Uh and we were lucky enough uh with Slough that that’s now rewarded the full half a million from the DFT um so I thought it’d be interesting to share because maybe not everybody sees the whole element of the entire project like this I certainly don’t normally but
Actually what did Slough do with half a million how did it actually get spent so it’s literally a breakdown of where half a million went um and the first uh 15 or so went on uh professional fees which included internal resources within Slough it included the sort of consultancy team
Which was made up primarily of myself from four-way Consulting and I can see Michael there from from Atkins along with one of his colleagues from Atkins as well making up the entire team so with that we were doing all the site assessments design Works contractor management financial management commissionings validations so
The full works the biggest single biggest chunks went on to the signals equipment supply and installation costs partnered up with Unix and in that they allowed us to get five pedestrian Crossings fully refurbished we had two shuttle working signals Under and Over a rail Bridge which are again fully upgraded movie
Control added above ground detection and finally an eighth site which is a sort of a reasonably medium-sized Junction Again full upgrade refurbishment adding and move control to allow this to be installed civil’s infrastructure which is from memory about 20 21 of the of the costs which I
Think is probably unusually low for a project of of this type um but we cherry pick sites that we thought were going to be straightforward we assessed quite a few sites designed about a dozen actually installed eight and we picked off the sites that we reckon we were going to be minimum
Civils works and quick to install um so we get kind of most bang for the buck and make sure we got things installed on but on time and hopefully on budget TM cost making out about nine percent and I was the guys uh some you know safe
Working room on site and the final costs associated with those eight site refurbs um was uh some cost for some power supply upgrades bring those up to standard and a little bit on some ttros where we need to get road closures in on the shuttle workings
And that leaves then a final 10 left on the pie chart and and this was something which you know is unusual for me was looking at the finances on this Slough some people might be aware having a bit of precarious financial position as a council been in section 114 for a
Couple of years now and slowly as as a council we’re unable to bring anything extra to this project financially so we had half a million that had been won we did not have an extra pound we did not have half a million and one so we had to
Manage this project with a fair degree of contingency on each of the sites in case we had some overspend and unexpected complexities as it turned out we picked simpler sites we didn’t use all of our contingencies so we had some left over and that left over then is what was the
Final missing part where we’ve been looking at doing some above ground detector Replacements replacing failed loops and ended life magnetometers and replacing a selection of comms routers as well uh replacing all the 3G routers with later 4G technology so that’s that’s where we spent half a million next project
Is um a little more technical bit of a move for coordination around around about something I’ve named here Goldilocks linkings it’s not too much it’s not too little it was something that was just right again project that we’d worked on with with Atkins example that follows is kind
Of a generic simplified example but it kind of explains what was going on well hopefully it does anyway as is uh fairly common um with roundabouts wanting to coordinate an upstream uh uh green with a downstream circulatory so to get the vehicles moving from that approach around the circulatory
And conventionally a mover while there’s more than one way of doing this using some pulse and hold bits we can use those to either extend a downstream green or to recall that green sooner and and actually try and get some coordination now when we started doing this we looked
At sort of doing this in you know in two ways whether we’re just using a hold or a recall and when we started with a um a hold so just of some fairly gentle soft linking waiting for the two phases to be in line and then holding there
We found we didn’t get sufficient coordination around the roundabout and we were building cues on the circulatory when we went to the other end of things and we started to put a recall in that does that um we found that to recall our Downstream circulatory phase to Green we
Have to terminate its opposing face and in this case the southbound movement and we were building a queue there so we were doing it sort of too little linking we got a queue on the circulatory too much linking we got a key on the opposing approach
And we wanted to strike a middle ground but we wanted to do that quickly on site without resorting to control special conditioning or you know even diving into mover version 8 conditioning because I have to admit I’m no expert on that yet so we looked what can we do that’s there
Conventionally and we used two particular settings in mover to actually give us this sort of Goldilocks this just right linking first of these feature that’s been around for a while ESL Max Ender saturation on a link and we use that on our southbound approach where we could
Build up cues and unusually there we set a a value which is much lower than normal and through a process of trial and error we settled on 20 seconds so we forced the end of saturation on those links after 20 seconds sounds counterintuitive but when we use
It hand in hand with bus waiting so this is where we took what was traditionally a conventional pulse link and priority link within mover we turn that into a bus weighted link and using some numbers which are probably better readable in the in the paper we put some numbers on there which
We just kind of guessed at based on some training we’ve done with TRL and they work straight out and what actually happens now when mover well when we get the Upstream green phase a goes green and it requests the recall to the downstream circulatory that recall only happens if its opposing green has
Reached endosaturation and the site is quiet mover has reached a natural end of saturation and it goes there no cue on the opposing link if it’s a busy then the we force the inter-saturation after 20 seconds through the ESL Max and at least then we guarantee an effect an effective minimum
Green on that southbound approach and we found that through that trial and error process that was sufficient to avoid us building sort of you know and you know unnecessarily large cues so we managed to strike this nice balance of not too much not too little and without diving
Into any sort of particularly special or hard to configure features within mover Oh dear and then moving on to the final site which I’ve kind of said it wasn’t meant to be like this this is the um it was the gift that kept on giving on this project so this kind of project actually we worked with with Atkins again and my
First involvement wallet with it was um I think right I’m going to turn to the turn of the Year where I was asked to cost up our design works and looking at the information that we had been given provided you know outline drawing of the site fairly conventional shuttle working
Three arms Bridge over River in um a really quiet basically part of the world Place little town called Crick Carroll in the Brecken beacons and for me actually it’s not that far from homes it’s quite nice for me not too far to travel costed this up yeah it’s a refurbished
Room shuttle working at a pedestrian phase app mover add some cycle infrastructure as sites go these days nothing sounding particularly out of the ordinary and that kind of turns this into as well as being interesting you’re just a sort of cautionary tale of just how hard can it actually be
So you see an image of the site as from the site visit I undertook a little bit later but still early in the year you can see fairly cold day and I was sort of get out the car let’s go and have a look at this site let’s
Find out what’s here and let something I’ll go and open up the signal controller go and see if we’ve got any old drawings and configurations that are going to give me some useful information about how the how this site runs and I couldn’t find it you’re thinking I’ve
Been doing this game for 20 years how can I not find a signal controller cabinet you know I know they could sometimes get buried in a hedge but it’s just I couldn’t find it and after you’ve been hunted and get on the phone and phone a friend and try to
Actually find this thing I found it and it’s some way I won’t move because I’m told not to move too much to the camera um can’t follow me it was a good 150 meters away from the nearest traffic signal head and on a completely different road to where any
Of the signals are on are you just sort of thinking what is going on here and then a little bit more thinking you think I think yeah that’s kind of obvious really this is a bridge this goes over a river Rivers can flood and uh in Crick Howell it can flood badly
And certainly in recent years has them and that signal controller has been moved just outside of the floodplain and it is only just but I mean recently I think the flood waters got within a few meters of it but that’s it all right well that’s at
Least we know why that’s there now we’ve got to deal with this how are we actually going to take account of this in our design because if our nearest signal head is 150 meters away our furthest signal head was over 300 meters from the controller and we start
Thinking elv a bit of voltage drop what are we going to do about this anything okay it’s not necessarily too bad with extra cable cores bigger cable or something we can counter that and then you think okay but that needs to go into some ducting how much ducting
Have we got her going over this bridge a single 100 Mil duct is all there was and we could put some more in maybe and it’s kind of now that bridge is listed that’s going to need special permission to dig it up and if we dig it up we’ve got to close
The bridge big diversions and nobody wants to do that so just okay um maybe we can find a way around this so okay we’ll keep other cables down but then you think I’ve got to add mover I’ve got to add mover Loops because the client would like to have loops but then
You say okay that’s more cable calls and if the further signal head is 300 meters my furthest Loop and the loop feeder is going to be pushing 400 meters oh okay right um I’ve got to use above ground detection which solves some of our problems and reduce the cable cause
So we sort of start going through but everywhere we turned we kept on finding problem after problem on this site which as an engineer is just challenge after challenge of finding a solution so some of the things we had to resort to above ground detection to cut our
Cable door cable cores down and the cable length the Cycles now the client here wanted to have cycle early release it can be quite a popular cycling area it’s also was primarily an active travel scheme to promote travel to the local school which isn’t far away and the
Client wanted to have an early release to get Cycles established on that bridge without having to have a car following them closely now the original intention was to go to low-level cycle indicators but you certainly think red to Amber green that’s going to be at least three calls
Before I work out anything else that might go along with it cycle filter it’ll do it yeah essentially the same thing slightly different but we still get a cycle early release that’s only going to be one extra call we had a pedestrian stage to add in
We’re just trying to get that fitted in within the stage sequence without adding in more delay because whilst it’s a quiet area this bridge is long there are some you know the integrating clearances are over 30 seconds potentially so adding that all in together has proved a
Challenge but we hope we’ve got that and you know to me it has been a really really interesting project it’s been one of the most technically challenging sites I’ve ever worked on but it also perhaps comes with a slight cautionary side to things because what I might find interesting also generally means time
And cost and I have to admit I priced this originally I didn’t think it was going to be this complicated we were on a fixed price agreement one of my bosses is sitting over there and um we’re kind of Christmas party fund that might have been slightly
Depleted this year so it has gone yeah the ads cost and complexity but it wasn’t anticipated it wasn’t sort of additional and sometimes sites can be like that so you know what may be interesting could also have a slightly cautionary side to it and that should be
Me and there’s no red light on so thank you any questions [Applause] John thank you very much three really interesting uh Clips there great outtakes given this is core incentive of what we all do are there any questions from the audience fair enough yeah can I while people are
Mulling ask you about the Krakow site and the cyclists yeah because I know that site and it’s a long Old Bridge it is it is a long bridge so you’ve got a couple of choices when it comes to releasing those cyclists yeah you can get them away and hold everyone
Else back for a while yep or you can get them away just a little bit excuse me a bit ahead of everyone else yeah and use them almost to platoon the traffic as well any thoughts on yeah it was opposed you know my view I I cycle regularly I’m
You know used to being out on and say I live not a million miles from here I’m used to being out on smaller lanes and narrow Lanes personally I’d far prefer to have a vehicle traveling slowly right behind me and the bridge is so narrow if you just cycle out a little bit
Um then you’re you’re in control as a cyclist but maybe not everyone’s as confident as me if you have someone who is really sticking to you know close to the curb somebody might be tempted to just try and squeeze past them and never having that longer
Um release to get them pretty much right in the middle of the bridge and the client’s preference was to go for this really long release um is controlled by a timer or will be when the site isn’t implemented yet it should be later this year it’s controlled there when we come to
Validate it offering a bike in the back of the car and um we’ll see how it goes and how it actually runs and what works out the best so um we don’t know we’ve got the two options it’s all in there in the conditioning to allow flexibility
Sorry Mike question out Darren the mic is on its way to you my arms are tired John hi Darren kev’s department for transport I was particularly interested to show seals to be killed about slower I’ve been the provider of that funding part it was it was interesting to see how an
Authority had spent in particularly interesting to see an authority that didn’t have additional resource to add to that and I just wondering I I again maybe slow can answer this better than you but but do you get do you get the feeling that they felt that was a
Successful way to fund the signal upgrades you did was it successful is it something you think they would want to do again in the future uh yes certainly would want to do again because any you know the amount of money with it within the council itself for for this sort of
Thing is absolutely zero at the moment it is non-essential until it falls over but I think the biggest thing that has really helped from this project is you know every time we turned on a site I could get some photographs send some before and after and certainly two of
Our befores the signals were off they had failed they couldn’t be resurrected at a couple of The Crossings and actually being able to go to the council leaders and sort of department leaders and say we have done this look what’s happened this is where the money’s gone
It is really I think highlighted both the need and that there is a solution and I think now there is a far better appreciation nation that something can be done to solve problems and I think it’s created more of a desire to to try to find funds to allow this to happen
Um and whether it’s actually I don’t think it’s identified anything yet but if certainly more comes along you know it’s it’s really established yes yes we you know we need that and would love more of it now thank you that’s really good feedback to take back into DFT so
Thank you for that thank you cool um are there any other questions from the audience the brains aren’t firing very well this morning are they um okay Tom thank you very much for a fascinating presentation always good to have you up the front here but I’ll let
You go now yeah lovely thank you very much thank you [Applause]