Traffic Congestion For Plumbers

People who drive and used to run plumbing companies always seem to have a lot to say about how highway networks should operate and congestion is often something which comes up quite often as their specialist subject.

Of course, anyone who complains about being stuck in traffic will always have a reason why their journey is essential and why everyone else shouldn't be driving. 

The Roman engineers who famously forged drainage systems from lead sheet to give us the origin of plumbing, also built a road or two in their time and even back then, traffic congestion was also a problem - to the point where Julius Caesar banned carts from Rome for the first ten hours of each day! Traffic calming was also a thing in Roman times and so it seems that we have been trying to solve the same problems for over 2,000 years. 

I wonder if the Roman drive time pundit, Dickus Lamborghini, decried the latest one-way system or the poor hardworking Licenced Sedan Chair Owners' Association complained about congestion at the city gates. Maybe Biggus Jobbus had a particularly nasty blockage in the local baths which took half the morning to get across Rome to clear.

Discourse on how congestion forms, moves and changes is often thought about as an closed system where limiting flow in one places forces flow in another. At the basic level, there are similarities with traffic and water, but they really only apply on motorways and strategic roads where there is no frontage development or kerbside activity and where access is limited - closer to the closed systems of water supply and drainage.

In an ideal hydraulic (a general term covering the science of fluids) system, one can very easily predict and therefore design for a desired flow. For example, temperature, pressure, cross-sectional area of a pipe, "roughness" of a pipe and gradient of a pipe are interrelated things for which we have developed scientific formulae. 

We know that in drainage pipes, the maximum flow is just under the pipe being full as we hit a sweet spot just before the roughness of the entire internal circumference affects the capacity. We know that for a given flow, if we reduce the diameter of a pipe, we increase the pressure. We know that where a pipe enters a watercourse, we need to do something to take the energy out of the flow with rip-rap to stop scour of the watercourse bed.

We can apply these principles to the more closed systems like motorways as the traffic flow is predictable, so long as we don't hit capacity limits. For example, on a motorway, we can roughly stuff 2,000 vehicles per lane per hour passed a given point, although with three or more lanes, the outer lanes tend to carry slightly less traffic as speeds (and so distance between each vehicle) are a little higher. 

This level of flow is influenced by the proportion of HGVs (which are slower than general traffic), gradients and junctions. The reason motorways have slip roads is so people can join and leave at motorway speed to reduce disruption in the flow as well as being safer. In general terms, this is all fairly easy stuff to predict and design for. The problems comes for motorways and roads like them where the traffic demand starts to exceed the flowing capacity. This is where this type of road can never be a closed system because of spatial planning and other things that influence how and when people travel.

If the rough 2,000 vehicles per lane flows, then it is actually less than the theoretical capacity of each lane. Once flows start to go much higher, then using the pipe analogy, we are moving from just under pipe-full conditions to the pipe-full conditions and so frictional aspects come into play. Someone changes lanes erratically, there's someone driving much more slowly than the general speed or someone tapping their brakes is enough to destabilise the flow and we get a ripple effect of people braking which can even lead to the motorway coming to a standstill very quickly.

This is why motorways operating with variable speed limits and controlled lanes can move higher volumes because an already controlled situation is controlled even more. It seems counter-intuitive, but a managed section of motorway operating with a lower speed limit and better lane discipline can move more vehicles per hour than under the normal motorway speed limit and conditions.

The graph above is quite handy to show what is happening (especially as it doesn't have numbers). The point on the right shows the optimum speed for the maximum flow per lane. Drivers are able to bunch up more closely than at higher speeds, lane changing is being discouraged and although people are moving more slowly than they would at normal motorway speeds, the entire collective of people are all moving efficiently. Once we move past that sweet spot, faster speeds actually means a reduced capacity because we need far longer gaps between each vehicle and lane changing or encountering a much slow vehicle disrupts the system. We have the community advantage of moving as one vs the inefficiency of the individual.

The analogy with water here is laminar vs turbulent flow. At the optimum speed (velocity for the scientists) through a pipe, the molecules in the liquid move forward in straight lines without interrupting their neighbours. Once the speed gets too high, things like pipe roughness starts to knock molecules out of line and they disrupt their neighbours which creates turbulent (or chaotic) conditions which reduces the capacity of the system.

Once you move to an urban situation, things start to change very quickly. Unless we are talking about an urban motorway, we tend to lose junctions which are grade separated and even where we do have it, ramps are often shorter. Traffic signals, roundabouts, side streets, bus stops, loading bays and crossings all work to reduce the capacity of a road. We are no longer able to predict flows based on the number of lanes, we need to base our calculations on the things which cause friction.

Interestingly, there another piece counter-intuitive thought to be found here and that's how Low Traffic Neighbourhoods can actually increase traffic flow on the main roads. Traffic turning into and out of side streets disrupts traffic flow (slowing down to turn, pushing out to get a gap etc) and with the pipe analogy, friction in the system increases. It also explains why for bus priority schemes, we often see zebra crossings replaced by signalised crossings. This is because people crossing the road on a zebra crossing are chaotic which causes friction. Having signals means what happens in the traffic model happens in the real world (well, it doesn't and I'll come onto that).

Signalised junctions are a significant regulator of traffic capacity. In general terms, if you have a series of approach roads which are all busy, a signalised junction will not be able to cope with them having single lane entry and so you'll start to see things like separate right turn lanes and multiple lanes on the approaches and exits so that vehicles can pass through in parallel to cope with the demands of the approaches. Like flows along a road, signalised (and other) junctions are subject to friction and turbulent flow. Traffic going through amber signals, parking on the exit, hesitation and other factors impinge on efficiency. 

A signalised junction will run well up to around 85% of the theoretical capacity because that other 15% is like the pipe hitting full and being succeptible to turbulence. Interestingly, you also find signalised junctions operating over 100% because drivers know them well and are prepared to take some risks with finding gaps or regularly passing through amber signals. Indeed, you can often spot someone who doesn't understand the local learned behaviour in such situations.

The behavioural side is a nice way to show where plumbing and traffic diverge. Traffic isn't actually like water. It is not actually like some vast plumbing system that that is completely under predictable control where flow and pressure can be precisely tuned and that's why zebra crossings are difficult to model. Traffic (in it's widest sense to include walking, wheeling and cycling) is underlain by human control, emotion and influence with inputs and variables which make it very much an open system and indeed, chaotic system.

This also explains why people trapped in motors in congestion get frustrated, whereas people walking in crowds or cycling on a busy cycle track perceive what is happening and adjust to it on the fly. People in crowds generally don't bump into each other, they do that little dance of negotiation. People cycling through busy intersections don't generally crash because apart from everyone coming off badly, they can negotiate in an instant from the cues that other people give out. 

Drivers simply cannot negotiate space in the same way as they would walking in a crowd, but the regulation of the space they move through is inherently against how people actually move (and in many cases want to move) which goes a long way to explain how people behave. The physical space needed to occupy and move to one aside, that's also why walking and cycling are very efficient at moving people and why they don't need controlling in systems away from motors. It also explains bad behaviour where people disobey the systems put into place to manage driving. Maybe if commentators thought a bit more about it, they wouldn't come across as right charlies.

Footway Parking Fail: Redux

This blog has been running a while and so I sometimes forget what I have written. This week I recounted a footway parking story on Twitter which I thought I had explained before, but it was actually a post from 2013!

Anyhow, I think this kind of thing is sufficiently important to come back at again and offer some more thoughts on footway parking. My basic starting position is I think that footway parking should be banned. In reaction to that position I often get a stream of whataboutism and reasons special cases need to be made, but I have heard it all and I don't care.

The big problem is that we have tolerated this obstructive behaviour for so long, it is going to be difficult to roll back, especially in the way spatial development has locked many people into auto-dependency.

Above is a snap I took this morning on the A12 Eastern Avenue. I don't know if this exact location had one, but there were certainly cycle tracks on the Eastern Avenue in the 1930s, but these days, the front gardens are paved for car parking and a wide strip of footway (and maybe former cycle track) is also given over to car parking. From a walking point of view, it really is a tiring and desolate trudge. Nothing to see or do, nowhere to rest and no shade. Does the footway parking add to this desolation? Well maybe, maybe not, but it certainly adds nothing to the street.

Above, is the photograph I used in my Twitter thread. The space left for walking, even if people had parked within the bays is minimal - certainly not wide enough for side by side walking. The Eastern Avenue example would at least let you chat (shout) with someone as you walked along which would take your mind off the monotony!

My two examples are from London where footway parking has been regulated for decades, although some boroughs don't seem to bother marking bays as they should, and some ignore the footway parking going on in back streets (as lack of enforcement would suggest). Some even have local exemptions for streets where nobody wants to grasp the nettle. Most of the UK doesn't have regulation and so it is a postcode lottery as to whether enforcement takes place.

Now you can get into the technical about footway width (and I often do). Inclusive Mobility (recently updated) tells us that footways should usually be 2 metres wide, 1.5 metres as a minimum and 1 metre for a distance of no more than 6 metres. The 1 metre "rule" is for where there might be a single piece of clutter like a telecommunications cabinet. The problem comes where there are regular obstructions as they sterilise a strip of footway.

The image above shows what I mean. The red strip is sterilised leaving an effective width of buff area. The green area is a local narrowing caused by a telecommunications cabinet. You can also undertake comfort analysis based on pedestrian flow and available width, but that's probably more about busy places anyway and my main beef is ordinary every day streets along which walking has been relegated to sometime to squeeze in.

With footway parking, whether regulated or unregulated, we are often left with the situation that a 2 metre effective width isn't provided (I prefer to use the effective width as that is the space in use for walking). Some local authorities, police departments and the public think that leaving enough space for someone to get by (in single file) is enough.

The street above is in an older part of Cambridge where footway parking has been marked (both sides) to give enough space to get other motors through. The walking experience here has people wedged against the buildings on one side and cars on the other. There is no space for side by side walking here - you cannot hold a conversation with a friend because you are forced into single file.

My Twitter thread got interest (I think) because the residents of the street seemed to put their every day "need" to park their cars above the far off and potentially remote possibly of needed to be rescued from a fire. It's interesting to me because very few people focused on the actual every day space left for people to walk along. This might partly be down to my fire brigade punchline and partly because we have become so accustomed to footways cluttered with cars.

It is hard to see where we go from here. In England, some organisations want to see rules around footway parking which allows and regulates it. The RAC thinks it's too complex an issue for a ban and one wheel up might be fine. Guide Dogs prefers to see a London-style arrangement which would allow it on a case by case basis, but as I have explained, London is very hit and miss in how it is applied.

As I said earlier I prefer complete ban because it is a simple rule to understand and very easy to enforce. If there isn't space to park, then you can't. My worry with a regulated approach is we have a government which doesn't like red tape or burdening the driver and a London-style approach simply means the highway authority would pass a resolution rather than actually having to public a traffic order that is open to objection and challenge. In addition, if guidance is issued, it would probably end up being consistent with Inclusive Mobility where minimums will naturally be attractive to councils and designers. 

Scotland is currently behind its footway parking ban which has already been watered down with exemptions. Wales is probably closer with a ban later this year, but again there will be exemptions. In Northern Ireland, the matter is currently being thought about and in England, there doesn't seem to have been much happening since October 2020 after options were consulted on (none of which were for an outright ban).

So there you have it. Footway parking is widely recognised as a problem. National governments are at different stages of looking at it, but the solutions either make it more complicated or waters it down. Why can't we tackle the problem?

Denial Of Service

The Christmas break is now a distant memory and I'm back on the weekly treadmill, looking forward to some warmer weather and some visits to look at new walking & cycling infrastructure.

The last job of the holidays was to get shot of the Christmas tree and fortunately, my local authority laid on a pop-up treecycling drop off point within cycling distance, so I hooked up my trailer and took our tree for a little trip before its final journey to be composted. As I was heading home in the freezing rain, I got thinking about what I would have done without this temporary facility and what the wider implications are.

I could have cut the tree up and home-composted it, but Christmas trees take a lot of time to rot down. I could have let it dry and burnt it, but it would take ages to dry (and yes, smoke pollution). I could have cut the tree up and popped it in a neighbour's green waste bin or I could have taken it to my borough's tip (reuse and recycling centre).

Sticking the tree in the neighbour's bin would have been fine with him, but I got the exercise doing my errand. The tip would have been a much longer ride, but given it would have been on 40mph+ country lanes for the last part of the journey, it wouldn't have been safe. 

As with many places, the green bin service has to be paid for (notwithstanding I had a free opportunity) and the tip is only really accessible by car (and there is only one in the borough). As a citizen, you either pay an additional fee or you have access to a car. This goes for bulky waste such as mattresses, refrigerators and furniture. OK, you probably wouldn't be able to take every bulky thing by cycle, but that's not even an option where I live. 

I have in the past done work at home which has generated timber and rubble which either couldn't be reused or was surplus (I do tend to keep potentially useful materials). This kind of stuff isn't collected by the council, even for a fee and so back in the day, having a car was handy to get rid of this stuff and to be fair to the local waste authority, this type of material does enter the recycling stream. The alternative would be to pay a private contractor.

In other words, beyond what is collected for free with the weekly collection, waste services in my area favour those who have access to a car and indeed, this is a driving subsidy. You can of course discuss how and what should be collected, but the service is not equitable. When you start thinking more widely, you can see just how much more of life operates with driving being either subsidised or a prerequisite for participating in society. This is beyond a simple infrastructure problem, it is rooted in how services are planned and designed. It is rooted in the very spatial planning system which governs us; and of course, it is political decision-making at all levels.

I can think about other services where I live. Luckily plenty are within walking and cycling distance (dentist, convenience store, primary school). Walking is generally easy, but cycling isn't helped by hostile local streets. Other services can still be walked to, but if you're time poor, then cycling should be the natural quicker choice, but again, the streets don't enable it. Perversely, it's safer for me to cycle to a big box supermarket on shared paths than it is to my closer local shops.

Then consider the nature of development. In my personal "15-minute city", I can get to a fast food outlet by cycle, but the local streets are a barrier. Given it's a drive through, there's car parking and no cycle parking, I'm not really their customer. My main town centre is a 20-minute ride, although there's a ring road to cross. My nearest hospital is a half-hour cycle ride, but it's edge of town and again, there's some awful roads to traverse to get there. Beyond that, I need to swap from personal power to a train, bus or car (expect we don't have one any more).

This hasn't overnight. Out of town shopping centres and retail parks were fashionable in the 80s and 90s. Planning from the 50s started to separate living places from working places which created the need to travel and in the 2010s, building conversion planning rules were relaxed so much, that my town centre lost most of its office space. Throw in new hospitals built on the edge of town (with prime town centre sites redeveloped) and the addition of car-centric housing on the edges, then no wonder things have got as they have.

We can also add signalised junctions which have no pedestrian crossings, crossings which take ages to get a green man and layouts which prioritise shifting motors over people and all of the other features deployed to try and manage driving created by the parasitic symbiosis with the planning system.

I advocate for infrastructural changes of course, but I think it is important to stop from time to time and consider the planning system which we are trying to mitigate against, because it feels like a losing battle sometimes. As well as redesigning how streets and places operate, we need planning authorities to step up and change how development and redevelopment operates in their areas, prioritising that which supports local trips made actively. This is quite daunting where national policy is so warped (England especially), but change is needed.

Then there's the politics. The last decades have seen services pushed out to the community and then centralised again with the changing domga of the ruling party and indeed where investment is made and cut. Some years back, we had sure start centres across our area which was great for having a service in walking distance. The modest building constructed for our local one has now been a private nursery for many years and the early years support has gone. We had 13 centres and now we have 7 which means people have to travel much further.

One thing I have more recently been exposed to through my structured continuing professional development is how walkable and cyclable places can strengthen community cohesion and as well as being able to physically easily get around, this includes have essentially services close by. Lots of smaller supermarkets which don't have car parking, vs a few large sheds with massive car parks. Local GP and clinic services rather than everything under a larger regional medical roof. Smaller local schools, rather than super-sized campuses which are hard to reach. Local independent retailers rather than chain stores in town centre shopping malls which outcompete the rest of the town centre. Being able to live locally is a highly resilient thing and doesn't rely on big centralised services operating.

This is a complex and interrelated subject, but my experience of getting rid of a Christmas tree is actually a fantastic example of what I am talking about.

Low Traffic Neighbourhoods: Back To the Future

Aside from the odd regulatory tweak such as low level traffic signals and parallel zebra crossings, the UK already had the tools needed to manage its highway networks all along - we just sometimes call them different things.

Low Traffic Neighbourhoods (LTNs) is a term which has been coined in the last few years, but the principles and ability to deliver them are nothing new. In 2016, I worked on an experimental scheme to deliver a signal modal filter to a street which was being used by drivers to bypass a section of trunk road which was congested at peak times. The scheme was really the last piece in a jigsaw which started in the early 1970s with the rest of the state. 

Cheap, not pretty, but it did the job for an experiment.

I am currently researching other schemes in my area (LTNs and other things) and so far I have found experimental traffic orders being used as far back as 1965 banning turns (1965 being the year the modern London boroughs were established). This old experiment was made under the Road Traffic Act 1960 which I think was the first piece of legislation that allowed the experimental process. There was then lots of activity through the 70s when many streets were filtered to keep through traffic on main roads.

An example of an early 1970's modal filter.

The 1960 Act had specific clauses relating to experimental schemes in London, although here we predate the modern London boroughs and so the traffic authority was actually the Metropolitan Police which could make orders with approval of the Transport Minister. For other parts of the country, it seems that the 1960 Act was also used, but on application to the Minister. On the establishment of the modern London boroughs and the Greater London Council (GLC), the traffic authority powers transferred to the GLC for Greater London.

I have been digging around the The Gazette where lots of public notices of all kinds are advertised and amazingly, I have found an experimental traffic scheme in Slough from April 1955 which used the even earlier London Traffic Act 1924, although this was for a parking management and a one-way traffic scheme which now seems to be part of a long pedestrianised part of the town. Anyway, my search for "experimental traffic" can be viewed here.

LTN schemes (whether experimental or not) create "prescribed routes" which is the legal definition of which classes of traffic may pass or proceed (although some authorities describe things a little differently). The search for "prescribed route" is even more astonishing. The earliest record I could find is from June 1838 and related to traffic management (carriages) for the coronation of Queen Victoria - it was required for:

"securing the commodious access and return of carriages conveying persons to and from Westminster Abbey, on the occasion of Her Majesty's Coronation."

Her Majety's State Carriage

(National Sporting Library & Museum Blog)

Have a read of it. The language and how the routes were kept clear contain language which will be rather familiar to anyone who has read a traffic order. This is essentially a temporary traffic order for an event!

OK, Queen Victoria's coronation was not linked to LTNs. Searching through the records under "prescribed route", we find lots of references which give powers to corporations building waterworks, tramways and other infrastructure to make byelaws which prescribe routes for traffic (with references to hackney carriages and omnibuses for example). In the 1930s, there are lots of roads having speed limit changes and actual modern ideas of prescribed routes such as a section of one-way working on Lea Bridge Road in London (in fact, one-way systems seem to have been very popular in 1930s London, along with roundabouts).

I have also been using "prohibition of traffic" as a search. Again, plenty of references to things being done to facilitate motor traffic flow because of road schemes. I have found a 1957 reference to the prohibition of traffic in High Lane, Hanwell (Borough of Ealing at the time), but it's not an LTN. As with prescribed routes, there are lots of prohibition of traffic orders linked to the construction of road and (motor) traffic schemes and trying to find something which fits the LTN bill seems to be really difficult.

April 1960 has an interesting reference to the centre of Horsham where a prohibition of traffic order essentially establishes a pedestrianised area in the the town. However, although there are some servicing exemptions, I think cycling is banned (as vehicles) which for my mind doesn't qualify it as an LTN and there are certainly "no cycling" signs in the pertinent area today.

In truth, it's probably not going to be possible to find the traffic order which established the first LTN as we might know the concept, but once we get into the mid 1960s we start to see things which are more familiar. In 1963, Mainway in Lancaster was closed to vehicles at its junction with Owen Road, although like Horsham, the order doesn't seem to have a cycling exemption. 

In 1964, Canterbury City Council sought to stop driving over the Whitehall Bridge Road railway bridge which today is filtered and maybe creates a local LTN. We can't tell from The Gazette what the "why" was for the closure. It may have been the structural integrity of the railway bridge or maybe the newer residential area would have generated too much traffic heading across it to the city centre.

Traffic in Towns (from the Urban Design Group)

In the 1963 Traffic In Towns report by Professor Colin Buchanan, the idea of the "environmental area", somewhere free from external traffic was established. This really is the original term for what we now call an LTN and it is no coincidence that this is really where we see the idea starting to spread. The urban planning profession was starting to understand the impact that traffic was having and maybe the coining of "environmental area" was a way of consolidating the things we had been doing since the 1930s in the same way that LTNs have consolidated the thinking of the early 21st Century.

The Railton LTN, installed as an experiment in 2020, 

now being made permanent.

Although we recognised the need to deal with through traffic in residential and local areas in the early 1960s, we also carried on with our big urban road schemes as well as expanding motorways that spat out traffic at each end. In the 2020s, we are living with that legacy which has subsumed local streets as the "pressure valve" lauded by high traffic proponents. In other words, we have used up capacity on main roads designed for through traffic and allowed it to expand unchecked into side streets. 

The other parallel is there is still a push for large road capacity upgrade schemes which will but additional pressure on local streets. It seems we have understood the issues for a very long time.

What Exactly Is A Design Classic?

There was a tweet doing the rounds the other day about how how ugly someone thought that a secure cycle parking shelter was with a suggestion that a design competition be held to come up with something better.

The person who posted the tweet compared the shelter with a farm pig shelter and thought that the place which developed the Routemaster bus, red telephone kiosks and black cabs could do better with a design competition as an idea.

The actual shelter being criticised was the Bikehangar like the one above by Cyclehoop which essentially provides six secure cycle parking places in the same space as half a car parking space. I will declare a modest interest here as I have done a little bit of work for Cyclehoop, although not on this product.

In general terms, this piece of kit does a good job with an efficient use of materials. From the conversations arising from the tweet, the only real criticism people had was that leaves and rubbish can get blown into the unit from below. The need for the unit is derived from places where people's homes cannot provide cycle parking internally and having cycles as easy to access as possible means they are more likely to be used.

There are other manufacturers providing competing systems with the common features of a large lid which can be opened up to get maximum access to the cycles for ease of locking and unlocking within, and a shell which has dimensions to maximise usable space inside, while not wasting space and therefore materials. 

Compare the hangar style shelter with a more traditional public cycle shelter (above) and it is clear to see the difference in terms of height and of course the additional security of the opening roof that a hangar. So, are hangars beautiful? Maybe, maybe not - that's always a personal view and hard to quantify. They are utilitarian and need to be affordable to procure and install which does rather narrow down the choice of materials. 

In terms of size, that is generated by the length of cycles to get the shelter width and the length of a unit will be limited by the size and therefore weight of the roof (even with gas struts to help with opening/ closing). They also need to be maintainable with the ability to keep them clean and to remove graffiti. You could of course use different types of cladding or maybe build the ends in brick, but that comes with costs, weight and maintenance issues. Once you move into bespoke, you pay for it.

Cornhill, Bury St Edmunds. A car park instead of a public square.

I have been seeing hangars pop up over London for the past several years and the common denominator has been that they are invariably placed within or at the ends of a run of car parking spaces and that is the elephant in the room. Parked cars take up significant amounts of public space, both physically and visually. It's not just the vehicles, it's the extent of asphalt, road markings and traffic signs which are needed to service them. Streets and squares (above) are subsumed into feeding our habit and that gets lost in the discussion.

I'm not against having a design competition for secure on-street cycle parking, although presumably a manufacturer would have to be involved unless the outcome is open-source. Design competitions are good for inspiration and for profile-raising to be sure, but I do struggle to see what design innovation is available, given various manufacturers have been delivering these for years now. 

I have always been a bit of a function before form person. This view has been forged in the furnace of countless arguments with people who fail to understand that there are users and maintainers to consider. I therefore have some long-held biases. 

However, I'm not convinced that the rotten accessibility of the old Routemaster helps its design classic status. Red telephone boxes are a nightmare to clean and maintain and black cabs are an expensive and space-hungry way to deliver transport in a city (although I actually like the shape of the hybrid electric version - above).

Something being a design classic or a design icon doesn't necessarily make it practical or useful, but personally, I think the Cyclehoop unit is a design classic which ably responds to the brief in a pragmatic and efficient way. By all means, let's have these conversations about the items placed within our streets, but let's not have these discussions in isolation.