Where is the best place for congestion?

I’m a firm believer in the idea that social change can be facilitated by good questions – that good questions can be very powerful.

We can’t avoid traffic congestion in our towns and cities. We can’t build our way out of congestion. We know this.

So we accept that our towns and cities will experience congestion, here’s a really important question…

“Where is the best place for the congestion?”

I think that it’s very important that we ask this question, and that we demand that people responsible for our streets and roads answer it.

We know that one of the factors limiting how many people drive, and how many vehicles are using our roads, is the capacity of these roads, and the willingness for people to spend time in congestion. The idea that more and more people will try to drive, even after traffic stops moving completely, is nonsense. It’s nonsense that many people believe, but it’s nonsense all the same. There’s always a limit. Provided that there are alternatives, when traffic congestion gets bad enough people stop trying to drive. They may be prepared to move to a new home, or to change their job, to catch public transport, or to walk or cycle. If it takes 3 hours to drive somewhere and 30 minutes to catch the train, and costs are similar, then they catch the train. If it takes 1 hour to drive and 15 minutes to walk, and if it’s safe to walk, then they walk. There might be days when traffic stops moving – but in general the actual capacity of our roads is a key part of what sets the level of vehicle use.

But of course there are always places in the road network which clog up first – parts of the network which regularly are at capacity. And by ‘at capacity’ I don’t just mean that at those points the roads are allowing through the maximum amount of traffic that they can allow – but also that people are waiting for the maximum amount of time that they are prepared to wait there.

To politicians or authority officers, improving traffic flow at these points seems a popular thing to do. But these limiting points in our road network are important. The congestion here is helping to prevent congestion elsewhere. If we allow more traffic here then the congestion has to move to other places instead. Even if we’ve increased the overall capacity of the network and traffic moves more smoothly for a couple of years, we still don’t win. It’ll soon be just as congested as it was, just with more vehicles, in different places to before.

So back to my question. If congestion is going to exist then where do we want it?

Should congestion be on an urban road outside a school, or in a shopping area, or in the centre of our town or city?

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Or do we want it to be on a road away from people? And can we actively use congestion in one place to manage traffic flow somewhere else?

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Many of those who are professionally employed in building or managing our roads and streets have been indoctrinated into the belief that they should at all times be working toward improving traffic flow. And they may never have thought about this question – which is why I think it’s such a good one to ask.

The myth of achievable flow

Back in the 1930’s or 40’s (or thereabouts) the world at large seems to have bought the dream of ‘automobility’ – the idea that a good life of the future would be based on door to door motorised private transport. In a world where few people had cars it would have been so easy to fall into the trap – becoming a believer – imagining a future of luxury where what sometimes feels like the tedious journey to work was exciting, quick, and effortless.

Surprisingly nobody seems to have been capable of doing the maths – looking at the size of vehicles, the size of our roads, the space needed for parking, and so on. Or at least they seem to have been so sold on the idea of building bigger and bigger roads they lost sight of the fact that people are social animals… so that destroying our city centres by building huge roads designed to get people to those same city centres was both illogical and wildly stupid.

In other places completely new towns were built, on the basis that automobility was the goal. There’s one a few miles from my home city. Houses sit on cul-de-sac streets which are directly connected to bigger streets, and then to a set of major distributor roads which are kept free of housing, human scale activity, and pedestrians (who are confined to separate paths linked by underpasses). The whole plan was to create free flowing traffic, and a modern way of life. It was idealistic – driven by a real belief that this would be a positive step. There can often be plenty of green space, and there was an aim of creating places full of fresh air and healthy people.

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But in general this failed, and failed miserably, creating relatively soulless towns, but with plenty of congestion remaining… because even when building completely new towns nobody was realistic about the huge amount of space that would need to be dedicated to roads for moving vehicles, and parking for storing them.

Nobody anywhere has managed to make this work, creating both nice places to be, and free flowing traffic.

Many many cities had a turning point, where they realised their mistake and turned back. Even the Netherlands with its bicycles and its traditional city centres followed this path. Utrecht is currently replacing an inner city centre motorway with the canal (moat) that was filled in many years ago to create the motorway. Amsterdam planned a wide city centre road and had made the space to build it, but changed its mind and instead put the medieval streets back in place. Birmingham, England, built inner ring roads and motorways suffocating the city centre, and has very very slowly been downgrading or removing these.

The Netherlands is notable because it didn’t just stop pursuing the automobility dream, but it came up with a new vision, and started struggling towards this many decades ago. Many countries, my own included, stopped pursuing the really radical plans to create free flowing traffic, but never really worked out a new vision.

I’ve recently been supporting some work to redesign an academic module introducing undergraduate civil engineers to road design. The old course taught – until last year –  how to build a motorway, and was based on the idea of traffic movement. The new course teaches about how different designs around our urban roads and streets have an effect on the lives of people who live and move about there. I think that this isn’t at all unusual – worldwide I suspect that many people working on our streets have been taught that real roads look like motorways, about flow, about controlling pedestrians, about gradients and kerb corner radii, but nothing or almost nothing about how to make urban streets better for people to live beside.

There are still many many people out there who have jobs connected with maintaining and developing our roads and streets who have come from this background – and who secretly are still believers (or half-believers), or who simply apply the tools they were given because they don’t know any better. Their city may have plans about cycling and walking and public transport, but deep inside they still assume that with sufficient political support and enough commitment the city could have free flowing traffic.

When they build, or maintain, or approve changes to our streets, they’re still thinking that they are working towards traffic flow – so little by little small (or large) changes are put in place with this in mind. If a corner can be made more gentle to keep traffic moving they make it more gentle. If traffic lanes can be added they add traffic lanes. If a junction can be changed so that it allows traffic to move through it faster then that seems to them to be a good change.

This is where our question becomes useful I think – because it’s very reasonable to ask this, but it forces the believers in flow to confront their beliefs.

Where is the best place for the congestion?

Other questions

There are equivalent questions – which generally mean the same thing or which ask people to think about the same issues:

  • If you improve congestion at this junction, where will it happen instead?
  • Why is it a good idea to increase the capacity of this junction?
  • Your policy says that the city is prioritising cycling, so doesn’t that mean that you should be trying to limit the capacity of this road to carry vehicles?
  • How is the city trying to direct congestion so that it can be in the best place?
  • Based on your traffic model, which are the junctions where their current limit on capacity is helping to control overall traffic volume in the city?
  • Why hasn’t anyone modelled this? Surely that’s an essential step?
  • Where are there sections of free flowing carriageway which could be narrowed or controlled so that traffic flows more slowly and congestion is decreased at junctions?
  • Where is there currently spare capacity in this road system, and what are you going to do to remove it so that these roads match the overall capacity of the system as a whole?
  • If you don’t improve this junction, when do you think it’ll reach capacity – so that people choose a different route?

See also

Comments…

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6 Comments

  1. Hi Robert, Simon Pickstone here, I have to tell you that I disagree with your primary premise: “We can’t avoid traffic congestion in our towns and cities”. I believe it is technically achievable using traffic controls, better urban design and planning, pricing, providing sustainable alternatives to the private car and to motorised road deliveries and by shifting from a private to a shared ownership model of motorised transport. If we use pricing, in conjunction with the provision of sustainable, high quality (mass) transit to substantively meet travel demand in cities, people and businesses will make the shift and congestion will be drastically reduced, more space will be available for more efficient uses. (Please note: These views are my own and do not necessarily represent those of my employer). For an interesting briefing on car-sharing see: https://www.transportenvironment.org/sites/te/files/publications/Does-sharing-cars-really-reduce-car-use-June%202017.pdf
    I do, however, accept that this is more of a challenge in the political and social spheres as opposed to the technical!

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    1. Hi Simon – excellent, I was hoping someone would disagree with me 🙂

      I suppose I should be clear when I say that we can’t avoid congestion. I don’t mean that our towns and cities internally have to have large queues of vehicles. What I’m getting at is that the queues of vehicles are an essential part of controlling/limiting traffic – and that they shouldn’t be in the middle of our towns and cities. I suppose I’m asking people to think of it like this. If we were running a theme park, we’d want to control the number of people coming into our theme park so that conditions inside remained fun. With that in mind we’d not keep adding entrance gates. We’d ask people to queue outside if there wasn’t enough space for them inside. While we might widen a few paths inside the park, we wouldn’t widen them so much that the place was spoiled. The queues outside would be one of the tools we’d use to control how the park functioned. It’s unlikely that we’d set our prices higher and higher so that queues never happened. It’s just as unlikely that we’ll see cities controlling traffic to such an extent that queues don’t happen.

      Of course this analogy is too simple – because it implies that our traffic comes from outside the city. Actually much of it is internal. But the basic principle still applies – that traffic should be controlled by limiting capacity.

      Which I guess is probably exactly what you’re also saying when you talk about control using urban design, traffic controls, planning and pricing?

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      1. Hi Robert, I am glad to contribute and always up for a constructive debate 😉
        I agree that congestion/queuing is an effective means of limiting/controlling traffic. I don’t agree it is essential or unavoidable and I don’t agree it is necessarily the most efficient either. Continuing with your theme park analogy (although our road network isn’t like a theme park in that ever increasing the number of users/visitors is beneficial), rather than making people queue at the gate, I would make a set amount of tickets available to pre-purchase – possibly based on the average time people take to work their way around so visits can be staged by the hour etc. That way people aren’t travelling to the park when there is no capacity or left standing in a queue when they could be doing something more productive? I accept that translating this into a traffic management system would be more complex, but not impossible. It would involve pricing and controls to ensure those people that have to get to the theme park at a set time can e.g. employees, and that those that have a choice chose the most efficient time/means or chose not to visit at all (pricing and mass transit points). I think setting prices, perhaps in combination with physical access/egress control measures, to achieve a manageable/efficient flow on our networks is completely plausible. In many places I would argue we have too much general road capacity already, so limiting that capacity further could make sense, especially if it isn’t needed because modal shift and mass/shared transport has been effective in parallel with pricing signals.
        Better urban design and panning – spatial location of homes, work etc. to minimise the need to travel and the distances required to access services.
        Traffic Control – Filtering, access controls/zoning (timing, mode, limit on quantity entering/exiting etc.), interchanges e.g. P&R, road space allocation etc. Daily limit/allowance on mileage??
        Pricing – charging & road pricing (e.g. CAZs).

        (Please Note: these are my personal views and not necessarily that of my employer).

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  2. I was excited to read that you’re getting a chance to influence the next generation of roadway designers! What were some of the highlights of changes you made to the curriculum?

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    1. Hi Matt. I’ve been involved working with a lecturer who’d made contact with me when he’d already decided that the module on ‘highways’ in the undergraduate course needed to change. The old course (not his responsibility previously) had very much been about motorways. I think probably that one assumption might be that this was a good starting point on understanding how roads should be built more generally. But the result really was (I think) to teach that all roads should be built like motorways. We talked through what the undergraduates might need to learn – this being their first encounter with roads as a part of civil engineering. In the end he decided on some key themes to cover. Most of the actual work was his, although I did support a number of tutorials.

      The details probably aren’t as interesting as the general principles. They were taught mostly (but not exclusively) about urban roads. They were introduced to some technical ideas, but also very much to the idea that designing roads isn’t something you can do by following a book of standards. And they were taught about why street design matters for people who aren’t themselves actually driving.

      Here’s where it got really interesting for me. I’d assumed that, being budding engineers, they’d want to work from standards and by numbers, but the opposite seemed to be true. While able to handle technicalities many of them actually thrived once given the opportunity to think for themselves. I talked a lot about how urban street design is an art, not a science – and how it needs creativity and observation and imagination.

      I made key points including these I think: Trying to design using standards as your starting point produces very bad street design (although standards have a role). Streets and roads are designed in some other countries (most obviously the Netherlands) to make them work in a substantially different way, and good engineers know about the differences and why they matter. Designing for flow creates bad design for cities and towns, although it’s appropriate on ‘flow roads’ like motorways. Good engineers should question everything about how roads have previously been designed, and not assume that something they’ve seen a lot of here in the UK is a good idea, nor that it looks the way it does for any reason other than fashion.

      What’s been exciting is that this work also prompted, or at least came to play a part in, some wider cross-university conversation. I think that there are a whole number of people questioning what’s taught at university about ‘highways’ and roads. I think that my main point to this wider group – in reflecting on what I’d seen – was that teaching has to be about road and street design as an art not as a science… and that this introduces interesting challenges (but challenges which with thought can be overcome).

      Liked by 1 person

      1. Wow that’s incredible to hear. As a product of the engineering education system I can relate to the reaction of the students when you gave then a chance to think for themselves – the first time I was given an assignment involving some creativity, I thrived! One of my career goals is to one day teach a civil engineering course much in the way that you’ve helped to do – lots of inquiry, observation, and multidisciplinary collaboration. We need the next generation of engineers to be prepared for the next generation of transportation systems!

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