Types of filtered permeability, and its effects

I suspect most people who read this and similar blogs are familiar with the term ‘filtered permeability’, and what it implies.

Maybe a better term is required; perhaps it isn’t particularly easy for the general public to grasp what it means. But it is certainly better than ‘road closures’, which has been used, problematically I think, to describe elements of the improvements in Waltham Forest. This is mainly because roads that have been filtered aren’t ‘closed’; they are still open as they were before to walking and cycling, and are still accessible to motor traffic, albeit by slightly longer routes than before.

This road isn’t really ‘closed’ – it’s still open to all modes of traffic. Still taken from this video

This ‘filtering’ can be achieved in a variety of ways –

• with bollards, or some other kind of physical barrier that stops motor traffic, but allows easy access for other modes
• through the use of one-way flow for motor traffic, carefully arranged to prevent through-traffic (but with exemptions for cycle flow in two directions)
• simple signs that forbid motor vehicle access (although to be self-enforcing these should probably look and feel like streets where people shouldn’t be driving)

The first form of filtering is quite obvious; the second perhaps not quite so obvious. Recently I illustrated how a large residential area in the centre of Utrecht has had through (motor) traffic entirely removed from it, with the use of one-way flow for motor traffic, arranged in different directions.

The blue arrows indicate directions for motor traffic; the red indicates the boundary of the cell. It is not possible to drive through this area, only to access it.

The result is streets are that pleasant and quiet; safe enough for children to play on, even without any physical barriers on the street.

One of the streets in this cell, Badstraat. You can see some of the one-way/no entry signs for motor traffic here, with exemptions for cycles

The final alternative is a simple signed restriction on motor traffic, without any barriers at all.

In urban areas, this kind of filtering has to be used carefully, I think, as signs like this are easy to ignore, or misunderstand. They should really only be applied on streets that look like places you shouldn’t be driving through; simply putting up this kind of sign on a conventional road isn’t going to be very effective.

“Pedestrian Zone” https://t.co/q3QvEQ7DeP

— Joe Dunckley (@steinsky) September 7, 2015

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But in rural areas in the Netherlands, and indeed elsewhere in Europe, this restriction is quite common, usually because it makes basic sense, once motor traffic has a faster parallel main road. We haven’t got around to employing this kind of restriction in Britain.

Having looked at ‘how’, the obvious next question is ‘why’?

From a cycling perspective, the main function of filtered permeability is essentially to create streets that are attractive to use, that can form part of a usable network composed of these streets, and protected cycleways on main roads. Filtering still allows motor vehicle access, but reduces motor traffic to a level comfortable enough for cycling to be a pleasant experience on the street, for anyone. This has been described as 100% separation by David Hembrow, and is also neatly summarised by Steve Melia in his new book, Urban Transport Without the Hot Air.

Separating cyclists from traffic does not mean building separate cycle paths on every street; separation can be achieved by strategically blocking streets to through traffic. The Dutch (in particular) have gradually built a network using a combination of quiet streets and separate cycle paths, which enables most people to avoid traffic almost all of the time – and to do so without significant detours.

Filtered permeability, combined with physical separation on main roads, creates a dense grid of cycle routes, a cycle network that connects up all the start and end points of potential cycle journeys.

Melia also makes the point that, while filtered permeability is an important part of a policy that creates direct cycle journeys, it also serves to make journeys by car less direct, and that this serves to make journeys by bike (and also by foot) relatively more attractive than they might otherwise have been.

This probably does have some kind of effect, although I think we should be very wary of overstating the ‘discouraging’ effect of making car journeys about 10% longer (or more, for very short car trips). Once you are in a car, it really isn’t all that much hardship to do a little more distance, because it does not involve any physical effort (which isn’t the case with walking or cycling). In addition you will find in the Netherlands that the routes drivers are directed onto, away from the residential or access streets that are no longer through routes, are specifically designed to allow easy, faster driving. In urban areas they will be 50km/h limits (~30mph), they will not have people cycling on the road, and they will add very little to journey times, despite being longer routes. What is really important is that bicycle journeys are as direct as possible; not that car journeys might be slightly longer in distance (if not necessarily in time).

Another reason ‘why’ is that this isn’t just about cycling, at all, as can be seen from the photograph of the street in Utrecht. Removing through traffic means that streets are safer, quieter, and more attractive, places where children can play, as well as cycle to and from their front door, in comfort. These kinds of benefits need to be captured more by an alternative term for ‘filtered permeability’ – whatever that may be.

One final (and I think unexplored) effect of filtered permeability may be on vehicle speeds. My hunch is that simple conversion of streets that once formed through-routes into access-only roads will have a lowering effect on vehicle speeds, even without any other changes to the design of the road or street.

I think this might be the case for two reasons in particular.

• Filtering changes the users of the street. A much greater proportion of drivers on the street will be people who live on it, or who are visiting people on it. The people who are using that street as a conduit to somewhere else will be entirely absent. Now of course many residents will still drive badly, or speed, on their own streets; but there probably is some effect in play here. I would like to see it examined.
• Filtering changes the directness, and length of street, on which speed can be attained. Look back at the map example of Utrecht, pictured above. Where once there were dead straight streets running from one main road to another for about a kilometre, filtering has cut out the straightness, meaning there is less opportunity to pick up speed. This would be the case without any changes or traffic calming on the street itself.

Warren Street in London seems to me to exhibit these potential effects.

Filtered permeability, Warren Street, Camden. Image taken from here.

Prior to this filtering, this street was an attractive shortcut for people travelling north, then west, out of central London – it allowed drivers to bypass the traffic signals at the junction of Tottenham Court Road and Euston Road, and also to bypass any congestion on Euston Road itself – the route shown in red. Motor traffic should be taking the route shown in green.

The bollards positioned halfway along Warren Street have changed this situation – they have removed it as an option for motor traffic attempting to bypass Euston Road, and the junction on it. The bollards (marked in blue) mean drivers now have no option but to use Euston Road.

What effect has this had on Warren Street? This is purely subjective, but my experience of this street is that, as well as greatly reducing motor traffic volume, motor traffic speed has reduced as well, without any other changes to the street (as you can see from the photograph). This might be due to a combination of changing the users of the street, as well as halving the length of road drivers can accumulate speed on.

What I would like to see, the next time a closure of this kind is implemented, is monitoring of vehicle speeds, to confirm whether this effect on speed is genuine, or imagined. The street itself shouldn’t be changed (at least initially) so the direct effects of filtering on speed can be examined.

Of course, there might have been research of this kind already that I’m not aware of – in which case, let me know in the comments!

Gridlock, and confirmation bias

Way back in 2003, the north side of Trafalgar Square – the portion in front of the National Gallery – was pedestrianised, with the road running in front of the gallery, that severed it from the square, removed.

Before the scheme was even implemented, it was ‘feared’ that gridlock would result, and indeed gridlock in the area continues to be blamed on the closure of this small stretch of road, particularly by cab drivers.

But even before this section of square was pedestrianised, gridlock still occurred.

Photograph taken from here

Trafalgar Square has always been clogged, even as far back as the 1940s.

If this short stretch of road in front of the National Gallery were to be reopened to motor traffic, perhaps motor traffic in the area might flow more freely for a short period, but after a while the ‘extra’ road space would inevitably fill up again, returning the square to its previously clogged state.

This is the nature of demand for road space in central London; demand for driving in London outstrips the amount of road space available (or that ever could be available), so whatever amount of road space that is provided, large or small, will just get filled.

The problem is that drivers in London don’t see things this way; the congestion they are sitting in must have been ’caused’ by this or that closure; that subtle change to the way the roads are arranged; that extra bit of pavement that’s been created; or, pertinently, that new bit of cycle infrastructure.

2) Every queue of traffic once the Cycle Superhighways have been complete will be credited to them. After all, there were no queues before.

— aviewoflondon (@sw19cam) September 4, 2015

This applies outside London too, of course. The inner ring road in Horsham has recently been subject to roadworks – minor changes to install a better pedestrian crossing – reducing its four or five lane width to just two lanes, in places.

Inevitably, these temporary changes are alleged have ’caused’ gridlock.

This overlooks the fact that roads in the town are regularly congested, even in the absence of roadworks. Again, demand outstrips supply, so people driving on roads in Horsham have in a sense ‘adapted’ themselves to the available supply of road space. We are seeing the temporary effects of some reduction in that supply. I say ‘temporary’ for a couple of reasons.

Firstly, these roadworks are on a road that didn’t even exist until the mid-1990s. It was bulldozed through, demolishing buildings, to bypass an existing two-lane road, and to open up access to a new Sainsbury’s supermarket. So it’s entirely possible to argue that traffic capacity – even with the roadworks – is still greater than it was in 1995. The new, wider road, has just been filled up in much the same way as the old one was; the difference is that this new road is four lanes wide, rather than two lanes wide. The roadworks – which are visible from your car, as you sit, stationary, in congestion, appear to be the proximate cause of your delay, but in reality motor traffic congestion is inevitable in urban areas. The number of people who might want to drive outstrips the amount of space we can give them, or at least should be willing to give them, without destroying the fabric of our towns and cities.

Secondly, people are rational. They will not sit in congestion, day after day, month after month; they will adapt. (Or at least, many will – and that will be enough). They will choose a different time of day to make their journeys by car. They will choose a different route, by car. They may even choose a different mode of transport (heaven forbid). Indeed, to return to the example that opened this post, the reduction of space for motor traffic around Trafalgar Square did not, in fact, create extra congestion on the roads in the surrounding area.

Problematically, this kind of behaviour is not addressed by modelling of road- and junction-changes. For instance, the ‘delay’ forecasts produced by Transport for London for the new Superhighways – which generated alarming headlines – assumed that people’s behaviour was fixed. That they would not change their time of travel, their route, or even their mode of transport.

Short-term increases in congestion caused by lane closures due to roadworks, or permanent reallocation of road space, will inevitably smooth out over time as people adapt, even if at the time it is apparently ‘obvious’ that those changes have created a ‘gridlock’ that would exist anyway.

Utrecht – a city that has been designed for cycling and mass mobility

I remember David Arditti once describing the experience of viewing pictures of Dutch cycling infrastructure, while sitting in a British conference a few years ago, as like seeing scenes beamed back from another planet – such was the difference between the road- and streetscape that we were seeing on the projection screen, and the familiar British roads and streets that we had encountered outside the venue, and indeed in the places where we live.

Much as I am now reasonably familiar with the Dutch city of Utrecht, every visit I make there has the a similar astonishing impression. Despite only being a mere 200 miles or so, as the crow flies, from south east England, the difference in the nature and character of the cycling environment in this city, and the nature and character of cycling in it, is so mind-bogglingly different to towns and cities in south east England, it really is like being on another planet. Indeed, as I write this, I’ve noticed a new piece by Andrew O’Hagan for the LRB which contains descriptions of London cycling so utterly at odds with nature of cycling in Utrecht – as we shall see in the pictures that follow – that the two places really could be on different spheres.

Andrew O’Hagan on London cycling

Anyway.

Perhaps the most striking thing about Utrecht is, of course, the staggering volume of people cycling, especially in rush hour, but also throughout the day. I have observed before how the ‘boom’ in cycling in London is essentially a commuter boom, limited to central London, and to the rush hour; cycling disappears from central London after 9am. This isn’t the situation in Utrecht; cycling is omnipresent, with what seem like continuous flows along the main routes throughout the day.

Typical cycling scene, Nachtegaalstraat, 12:30pm. Children are in school at this time.

This is the case both on the main roads – which naturally have separate cycleways – and also on the streets which form useful routes, but have low motor traffic levels.

11:30am, on the Oudegracht.

At peak times the flow becomes a flood, a dense mass of people on two (or more) wheels.

Cycle flows on (brand new) Vredenburg bridge, 5:15pm

As is clear from these pictures, the other reason why cities like Utrecht feel like another planet is the character of the cycling itself. People who are cycling are dressed just like pedestrians. Helmet-wearing, and hi-viz clothing, are totally absent. As Chris Boardman puts it in this wonderful video –

I’ve spent a couple of days riding around the streets of Utrecht, and I’ve seen tens, if not hundreds, of thousands of bikes, but I haven’t seen a single cyclist. I’ve just seen normal people, in normal clothes, doing normal things, dressed for the destination, not the journey. The bicycle is a simple, fun and inexpensive way to get from A to B.

Indeed, the only hi-viz clothing I saw in five days in the city was worn by police officers, and by the construction workers directing people cycling at the temporary junctions through the construction site by the railway station.

Some people in hi-viz – but these are workers stopping traffic.

Apart from racing cyclists, heading out of the city in lycra of an evening, helmet wearing amongst adults was non-existent; amongst children, a tiny minority of those perched on their parents bicycles had been given a (usually far too large) helmet to wear. Children riding independently, however, were also entirely unhelmeted.

The behaviour of people cycling is also ‘pedestrian’. By that I don’t mean that they travel at walking speed, but that they engage in activities they would be engaging in, if they were walking. Chatting side-by-side; listening to music; eating; carrying objects; talking on phones; travelling along with a dog beside you; and so on.

This behaviour, and this absence of safety equipment, isn’t because of any innate rebelliousness, or lack of concern for safety. People are just responding to the environment they find themselves in. Cycling in the city looks and feels safe – principally because, thanks to the design of the environment, it is safe. Interactions with motor traffic are minimal, or non-existent. On the main roads you are clearly separated from it, as in the photograph above; on side roads, design ensures that the only motor vehicles using these streets will be doing so in order to access properties on it, meaning motor traffic levels are very low. People can relax, everywhere, and that is reflected in how they behave.

Likewise, a good sign of a safe and attractive cycling environment is that children who are old enough to ride a bike do so themselves, rather than being ferried about on their parents’  bikes. Perhaps this wasn’t quite as common here in Utrecht as in a city like Assen, (this may have something to do with slightly longer trips in Utrecht, it being a larger city) but nevertheless young children riding independently was a common sight.

Children were even giving each other backies, on some of the busiest roads in the city.

My impression was also that women formed a distinct majority among people cycling in the city – certainly during the day. Rush hour was more balanced, but it was not unusual for me to arrive at traffic signals and find myself the only male queuing at the lights.

Cycling here is a mode of transport for everyone. Nobody is excluded from cycling. From what I could see ethnic minorities were cycling around just the same as everyone else, on exactly the same types of bikes, in the same way.

For those with mobility problems who can’t ride a conventional bicycle, the city is far, far easier to navigate than a British one – an environment designed for cycling is equally suited to  hand cycles, mobility scooters, assisted trikes, and powered wheelchairs.

Law- and rule-breaking by people cycling is at a very low level, mainly because there are few laws to break, and because the city is set up in favour of people cycling and walking. The environment supports you in where you want to go, in safety and comfort; you don’t have to choose between bending rules and avoiding danger, or avoiding inconvenience, because safety and convenience is built into a ubiquitous network. Where there are rules that people can break, people generally obey them, because the rules makes sense, and because there are reasonable alternatives. (There are, of course, anti-social idiots on bikes, but they are drowned out by the mass of everyday people behaving normally and sensibly).

To give just one example, cycling is banned on a busy shopping street during the day, and from a short period of observation, I would estimate that around 90% did comply with the rules, and dismounted.

People dismounting and walking on Choorstraat.

But this isn’t because Dutch people are any more compliant with rules than Britons; if you are travelling in this direction by bike, there is a parallel route just yards away where cycling is allowed, so naturally people travelling through will use that route instead. The people dismounting on this street are happy to do so because they are only travelling a short distance to shops on it. This contrasts with the typical British situation, where cycling bans are implemented on pedestrianised streets which are very often the only attractive and safe route from A to B. If you want people to obey rules, they have to make sense.

Admittedly this ubiquity of cycling (and of mobility aids on cycling infrastructure) does present some problems. The huge flows can be mildly irritating for people on foot at rush hour; there were some occasions where I had to wait 30 seconds or more to find a suitable gap to cross a cycleway safely, as did others.

Waiting for a gap to cross the cycleway at peak times

To be clear, this is only a problem that exists for a short period of the day, and even at these times natural gaps do present themselves, and the wait is, of course, much shorter than one might expect at signal-controlled crossings of a road carrying around 50,000 people per day (on buses and on cycles). But I did find myself wondering if there are ways of resolving this issue.

Other problems present themselves in the volume of bikes parked on some streets – especially the narrower ones that still serve a through-function. Voorstraat, in particular, is not a brilliant pedestrian environment. A genuinely narrow street has one-way flow for all traffic, including cycles, a protected cycleway running in the opposite direction, and ungenerous pavements. Notably, a supermarket on this street had at least 100 bicycles parked outside it.

Cycle parking on Voorstraat

The pavement on the other side becomes increasingly narrow, with bicycles leant against buildings; buses thunder through on the road, heading towards the centre of the town, combined with access motor traffic. On an earlier trip a few years ago, I saw children cycling on this road, being tailgated by one of these buses.

Cycling on Voorstraat

It’s a far from brilliant cycling or walking environment. But the problems with this street would be much, much worse without the levels of cycling in the city. That supermarket would have cars coming and going, clogging the street. There would be most likely be two-way flow for motor traffic, presenting more danger and difficultly to people walking on the pavements.

Indeed, in general, the minor irritations and inconveniences one experiences on foot are vastly outweighed by the benefits cycling brings. Mass cycling goes hand-in-hand with a highly pedestrian-friendly city. The entire ‘old’ city centre of Utrecht is effectively an autoluwte, or ‘nearly car free’ area.

The area outlined in red measures approximately 2km by 1km, and represents the original fortified city, surrounded by canals. Today, it is a low motor traffic area, dominated by walking and cycling.

You can drive here, either to car parks, or simply to access properties; but from the way the streets are arranged, you won’t be driving through. Motor traffic in this red area is therefore at a very low level, meaning roads that at face value are ‘shared’ with motor traffic aren’t really shared at all.

Typical access road layout in the north of this area. All the streets in the photograph are accessible by motor traffic, but designed not to be through-routes.

It’s very easy to wander from one side of this area to the other without encountering a single traffic light. Indeed, there are only a handful of junctions with traffic lights within the ‘zone’. That means there is little or no delay to journeys on foot or by bike within this area. It’s cycling that allows mobility into and across it, that provides the viable alternative to the car, and that means, consequently, it is such an attractive environment. It is ubiquitous cycling infrastructure, allowing easy, comfortable and painless door-to-door journeys, that actually contributes to ‘placemaking’.

It should be stressed that this is a city of some 340,000 people, not some minor town. Utrecht ranks just outside the top ten English cities in terms of population. Yet it feels extraordinarily calm, peaceful, and civilised. Sitting at a bar of an afternoon, you can see people travelling past spotting each other, waving, saying hello, or stopping for a chat. Transport here brings people together, rather than separating them. We would do well to learn these and other lessons from such a brilliant city.

Stress test

There was a typical August ‘silly season’ story last week – the idea of women-only train carriages, prompted by some comments from a Labour leadership candidate that were seized on and used to generate ‘news’ at a typically quiet time of the year for the media.

Without wishing to re-hash that story, there was an interesting comment on it, in relation to cycling design, from @accidentobizaro –

If we agree solution to drivers harassing cyclists is segregation, why shouldn’t solution to men harassing women on trains be same? #thought

— Andromeda (@accidentobizaro) August 26, 2015

This is a thought-provoking point; it implies that people who are in favour of separating cycling from motor traffic (at least on busier roads) should also be in favour of separating women from men on trains (if women want to be separated).

But I don’t think the analogy quite stands up. ‘Harassment’ is of course one reason why separation of modes makes sense. Walking on footways greatly reduces any harassment you might receive from drivers. So, with an equivalent separation of cycling from driving, harassment from drivers will diminish in the same way.

These people in the Dutch city of Zwolle can’t be harassed or intimidated by the drivers in the background.

But, with train passengers, I suspect most people don’t think women and men should be separated on trains, because the behaviour that is causing the problem should be addressed in the first place. Men should not harass women; if they do, they should be dealt with, rather than providing a separate (and allegedly safe) space for women.

But harassment is not the only reason why separation of the kind shown in the photograph above is provided. Even if we could stop drivers harassing people cycling, separation is still vitally important. We can see why by entering an alternate reality, one where ‘train separation’ is being argued for. But this is an alternate reality designed to resemble the situation on British roads.

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Let us imagine a situation in which a good number of people in train carriages are in the habit of… throwing and catching bricks. Not all, but a sizeable proportion. You could say, it’s what the British do, on trains. (A bizarre situation, but bear with me).

The vast majority of people throwing and catching these bricks are doing so with regard for other people. They’re doing it carefully, and trying their best to ensure their bricks don’t hit other people, be they brick-throwers, or non-brick-throwers.

But of course a tiny minority will throw their bricks recklessly. These are the anti-social minority, who don’t really care about other people, and are just lobbing their bricks, willy-nilly, without thought for others.

Let us imagine Britain has clamped down on this behaviour, over a period of decades. There are stiff penalties for reckless and anti-social brick throwing; repeat offenders are banned from trains.

This policy has been a success for a long time. Dangerous brick-throwing is almost entirely eliminated. The only people throwing bricks on trains are doing so carefully. You will almost certainly never encounter a reckless brick-thrower on a train. Only considerate, thoughtful ones.

Despite this success, let us now suppose that people have lobbied – successfully – for train carriages where you won’t encounter brick-throwers.

Would you choose to carry on sitting in the carriages with brick-throwing, or would you now opt to sit in these new carriages?

We might go further and even imagine that all brick throwing in train carriages will – at some point in the near future – only be carried out by robots, highly advanced robots, who will never make a mistake with their brick-throwing, and will never hit a fellow passenger. You would be perfectly safe to sit in one of these carriages.

Again – would you choose to sit in this brick-throwing carriage? Or would you instead opt for the carriage without brick-throwing?

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The answer to both these questions is surely quite obvious. Faced with a choice between a environment in which potentially dangerous objects are occasionally coming close to you, and an environment in which these hazards are absent, nobody would opt for the former environment – even if those objects are being thrown by human beings who are carefully considering your safety, or by perfect robots.

This is why separating cycling from motor traffic is important. While bad behaviour and harassment by drivers is undoubtedly an issue, the bigger problem is that cycling in motor traffic is de facto needlessly stressful, regardless of how well or badly motor vehicles are being driven around you. The experience of cycling in motor traffic may not strictly correspond to sitting in a train carriage where bricks are occasionally being thrown – benignly, and competently – but the reasons why people might want to avoid such a train carriage correspond closely to the reasons people want to avoid cycling with motor traffic.

It’s the knowledge that you might come to harm; the visceral sensation, rational or irrational, that your safety lies in the hands of other people. It’s the uncertainty and stress of having to negotiate your way through environments where heavy objects are travelling at different speeds, and angles.

These problems might be ameliorated by perfect behaviour, but they will still remain to a large extent, even if motor cars were driven by robots. It’s why we don’t stand close to the platform edge when a train is arriving, even if it might be perfectly safe to do so – the human body instinctively flinches away from heavy objects that are travelling at greater speed, and that have the potential to injure you.

We also want some leeway of our own to engage in less than perfect behaviour. It’s stressful having to maintain constant vigilance, and ‘correct’ technique. We’d like to be able to look around at our surroundings; to pay a little less attention to ensuring that we don’t come to grief. To lower our guard.

The Dutch cycling environment (when it is done right, of course – the Dutch still have problems, and still make mistakes) removes these kinds of stress from everyday trips. It makes ordinary journeys a relaxing and painless experience, free from concern or worry, from door to door.

This mother was happy to let her young child speed off ahead – because the environment is unthreatening.

This is what I enjoy so much about cycling in the Netherlands, wherever I go, be it countryside, suburbs, or city centre – it’s the total relaxation, the complete lack of stress.

The removal of through-traffic from streets that are ‘shared’ makes them equally relaxing.

There are exceptions, of course. What might actually be relatively comfortable environments, by British standards – low speed roads, with quite low traffic levels – leap out jarringly from the smooth, comfortable background experience.

The road in front of Zwolle station. Not remarkable by British standards – perhaps even relatively pleasant – but jarringly uncomfortable.

Nobody was misbehaving, or driving badly, on the road in the picture above, but cycling along it felt so much more unpleasant than the rest of my journey that day. The uncertainty of worrying about parked vehicles potentially moving in and out; whether drivers were going to turn across your path into side roads; whether the cars, buses or lorries behind you were going to get too close, or attempt to overtake inappropriately. The ‘concern load’ was so much higher here, I simply wasn’t able to enjoy myself. But this is pretty much the everyday experience of cycling in urban areas in Britain.

While I can tolerate cycling on these kinds of roads, it’s precisely these raised stress levels that put the vast majority of people off, entirely. This blogpost, from a Dutchman experiencing cycling in London for the first time, captures this problem well –

by Dutch standards you will be overwhelmed with a feeling of thorough unsafety when [cycling] on the roads.

And this is from someone who is used to cycling; a person who cycles every day in the Netherlands.

People like me – reasonably fit, experienced, male, middle-aged – can adapt to these environments, put up with them, and find ways to survive in them. People not cycling already simply won’t cycle in these environments, at all. That’s why cycling levels are so pitifully low in Britain. Mass cycling depends on low-stress environments; streets and roads that invite cycling, and make it as comfortable and enjoyable as possible.

People choose to live on quiet streets – so why is it so hard to close residential streets to through traffic?

An interview with the founder of housebuilder Redrow has been floating around in my drafts as a potential basis for a post for a while. It caught my attention because it touched upon residential streets and how they should be designed – and in particular, how we should address the issue of designing motor traffic out of residential streets (through traffic, that is – motor traffic should still be able to access residential properties).

The Dutch approach to road design – Sustainable Safety – is quite explicit that roads and streets should have a single function, with a principle of Monofunctionality. As Mark Wagenbuur explains, in a joint post on David Hembrow’s site –

To the Dutch the most ideal situation is when roads and streets have only one single purpose. To achieve this mono-functionality a hierarchy of roads was introduced.

• Through Roads for high volumes of fast traffic on longer distances.
• Local Access Roads from which end destinations can be reached.
• Distributor Roads which connect through roads and local access roads.

All Dutch streets and roads have been classified (under a legal obligation) and are or will be re-designed to the Sustainable Safety principles by the road managers. This led to areas where people stay (residential areas and areas for shopping/sporting/theatre etc.) and designated space used for the flow of traffic in order to transport people from A to B. Under the Dutch vision these functions cannot be mixed.

It is this approach that explains why Dutch roads and streets work so well for all users. In particular, access roads are designed to have low levels of motor traffic, meaning they are safe and attractive.

Residential street in Utrecht; motor traffic can access this street, but careful arrangement of one-way flow means it cannot be used as a through route

Strangely enough, it is this detail that is touched upon in the interview with Steve Morgan of Redrow. I’ve highlighted the relevant passage in bold.

House builder Steve Morgan has hit out at housing designed to meet the “urbanist” principles promoted under New Labour’s now defunct Richard Rogers-inspired planning guidance.

In an interview with BD’s sister publication Building, Steve Morgan, the founder of Redrow who rejoined the business in 2009 when it hit difficulties in the credit crunch, said that the housebuilder’s adherence to PPG3-style design was one of the main problems with the firm and hailed the return of the cul-de-sac.

Redrow had been building high-rise flats available at low cost but Morgan has subsequently completely redesigned the firm’s product range around traditional homes with arts & craft movement-inspired detailing, arranged in cul-de-sacs.

Morgan told Building: “We’ve got to start producing the type of housing that people want to live in, not some theoretical designs with ‘permeability’ all over the bloody place, which actually means traffic. Who wants tarmac all over a development? I want cul de sacs, green spaces, safe spaces for children to play in – not permeability, that’s just bullshit jargon.”

PPG3 was introduced under the tenure of deputy prime minister John Prescott and was inspired by the conclusions of Rogers’ Urban Task Force. It recommended higher-density developments to make public transport viable and create street life based around “walkable” neighbourhoods. But house builders said it resulted in building a large number of developments of flats without gardens which became very hard to sell when the credit crunch hit.

Morgan added: “It seemed to take forever to convince planners that PPG3 was history and we had to get on and build traditional housing again. It probably took the best part of three years. They have got the message now. Absolutely nobody’s doing PPG3-type development anymore but it took a while to get that through.

“We had highways engineers quoting the manual for streets and all the rest of it. [I] said, ‘Bollocks, bring the cul de sacs back, bring the type of housing that people want to live in back’.”

This is, I suspect, some fairly self-serving rhetoric from a developer with an interest in building low density (and therefore more expensive) housing, rather than higher density (and therefore more affordable) flats and housing. And it also comes from the perspective of someone who it seems can only imagine people moving around by car; permeability can work (and indeed should work) in residential areas, provided it is permeability of a specific kind, for walking and cycling.

But the passage I’ve highlighted is revealing – it shows that housebuilders are more than aware that the general public don’t want to live on traffic-clogged streets. They want to live on streets where their children can play safely; where there isn’t a huge amount of tarmac required to facilitate the through-flow of motor traffic; where there is green space.

Popular streets to live on are those that are quiet and safe; unpopular ones are those that are noisy, polluted, and dominated by motor traffic.

Not such a good street to live on – a residential street in Leicester dominated by through traffic, despite a parallel main road just a few yards away.

Given all this, it is surprising why proposals to close residential streets to through traffic often meet with such vociferous opposition from the people who live on them, on the grounds that the journeys they will make by car will become marginally longer – perhaps only a few hundred metres or so.

Because, with a free choice, the vast majority of people will choose to live on a street that is (effectively) a cul de sac to motor traffic rather than a through route, even if that means their car journeys are slightly indirect. The benefits of living somewhere nice outweigh the benefits of straight-line car routes.

So what’s going on? How do we explain this discrepancy between the choices people actually make, and the difficulties in ‘converting’ a poorly-designed street into an environment people would choose to live on in the first place?

My guess is that the benefits of a street being closed to through traffic can’t easily be appreciated – residents can only imagine their street as it is now, but with a bit of extra inconvenience for motoring trips, rather than imagining a safer, quieter and more pleasant street, one they easily would have chosen to live on, given a blank slate.

An interesting way of tackling this issue might be come at it from the opposite direction – to conduct a survey of streets that (by accident or design) only serve an access function in a given British town or city. My idea would be to ask the residents on these streets whether they would prefer their street to be opened up as a through route – ‘filtered permeability in reverse’. To ask them whether they would be prepared to trade off the attractiveness of their street for more direct car journeys, but with a (potentially large) increase in motor traffic on their street.

Maybe there aren’t any easy answers though – human beings are fundamentally conservative, and dislike change, even if the benefits can be presented in an attractive and easily understandable way, and even if the benefits come to be appreciated by residents who were initially opposed. I suspect the only concrete way of making progress is councils taking bold decisions, in the form of trial closures of a suitably long duration for the benefits to appear.

Deaths on the road

It goes without saying that the crash of a plane onto the A27 on Saturday was a terrible tragedy, an incident in which at least 11 people died, and many more were seriously injured. Rightly, the crash is being investigated thoroughly, and undoubtedly measures will be taken to greatly lessen the chances of any similar kind of incident ever occurring again.

But what has happened following that crash on Saturday afternoon? On the same day – the 22nd August, shortly afterwards, a motorcyclist died in Manchester, a pedestrian was killed in Solihull, and a driver died on the M1.

On Sunday 23rd August, 3 people died in a car crash in County Down, a motorcyclist died on the A82 near Loch Lomond, a cyclist died in Essex, a motorcyclist died in the Peak District, a driver died in Lincolnshire, a motorcyclist died on the A40 in Cheltenham, and a driver died in the New Forest.

On Monday 24th August, a teenager died in a motorcycle crash in London (with another teenager seriously injured), and a motorcyclist died on Anglesey.

On Tuesday 25th August – two people died in a car crash in Doncaster – with one (and maybe two more) seriously injured, a driver died in Camarthenshire, and a driver died (with another driver seriously injured) on the diversion route from the A27, closed following the Shoreham crash.

The scene of the crash in Doncaster.

This means that in the three and a half days following that dreadful air crash, 18 people have died on the U.K.’s roads, in crashes that, because they occurred in isolation, and because they are so appallingly ordinary, won’t make any headlines, or any lasting impact, beyond a fleeting mention in a local newspaper.

No lessons will be learned; nothing will change. All part of everyday life in Britain.

The 85th percentile as a tool for improving roads and streets

The “85th percentile” speed is a speed at which 85% of traffic will be travelling at, or below, along a street or road (under free flow conditions). It’s typically associated with the setting of speed limits, and (more controversially) often used as an argument against lowering them, or enforcing limits.

In particular, some police forces have been reluctant to enforce 20mph limits that have been introduced on roads that previously had a higher speed limit, without any changes to the design of the road, on the basis that enforcing this lower speed limit will prove to be too much of a drain on their resources – too high a proportion of drivers will be exceeding the new (lower) limit.

I have to admit I have changed my position on this issue over the last few years. Previously, I had been of the opinion that a speed limit is a speed limit, and that it should be enforced, regardless of how many people are breaking it. That any refusal to do so was effectively a ‘cop out’ (excuse the pun) on the part of the police.

But I think the police (or ACPO) are exactly right when they say

Successful 20 mph zones and 20 mph speed limits are generally self‐enforcing, i.e. the existing conditions of the road together with measures such as traffic calming or signing, publicity and information as part of the scheme, lead to a mean traffic speed compliant with the speed limit.

To achieve compliance there should be no expectation on the police to provide additional enforcement beyond their routine activity, unless this has been explicitly agreed.

In other words, the 85th percentile speed (the speed at which 85% of drivers are travelling at, along a road) should correspond much more closely with the posted speed limit through the kinds of measures the police list here – in particular, the design of the road. Research carried out for Manual for Streets shows that the speed at which drivers travel along a road is influenced by its design – principally its width, and forward visibility. If plenty of people are breaking a limit, that probably tells you either the limit is wrong, or the design of the street is wrong. Something has to give.

And this is the reason I am suggesting that the ’85th percentile’ could actually be a force for good – it cuts both ways. While it can be used to reinforce the status quo, it can also tell us that the design of a road is inappropriate for the posted speed limit.

Take, for instance, a situation in which a residential street with a 30mph limit has that limit lowered to a 20mph limit, without any changes to the design of the street, or to the motor traffic network. Let’s then say that the 85th percentile speed of motor traffic on this street, after the introduction of the lower limit, is much more than 20mph – close to 30mph, for instance.

What does this tell us? It tells us that the design of the street isn’t doing its job. While it might be a good idea in the short term to get the police out with speed cameras, a long-term solution should be to change the nature, character (and usage) of the road so that the 85th percentile speed on it is much closer to 20mph.

So the 85th percentile is an effective way of demonstrating when speed limits and road design are out of kilter. Take, for instance, this 20mph limit on Midland Road in London, running between St Pancras and the British Library – just one of many main roads in London that have, in recent years, had their limits lowered from 30 to 20mph without any change to the design of the road.

I don’t know what the (free flow) 85th percentile speed of motor traffic is here, but I’d be willing to bet good money it is way, way over 20 mph – this is a wide road, with three lanes of motor traffic bearing down on Euston Road, in one direction.

Again, we could get the police out here with speed cameras, but really, the discrepancy between the posted limit and the way people are actually behaving on the road tells us that something more serious is wrong here – the messages the road is sending out to drivers don’t correspond to the limit that has been painted on it. Something has to give.

By contrast, in this early-1990s 20mph zone in Horsham – designed to be self-enforcing – it’s pretty much impossible to drive at 20mph (despite it being one-way!).

A combination of speed humps, tight corners, limited forward visibility and surfacing means that the 85th percentile speed is likely to be at (or even below) 20mph, which tells us that the speed limit and the design of the road are in agreement, and there’s little or no need for enforcement.

The same logic can be applied to 30mph roads too. This road in Wageningen, NL, has a 50km/h speed limit – and it’s reasonable to assume that the 85th percentile speed will be at or below that speed, due to the design of the road.

The carriageway is very narrow, with motor vehicles barely passing each other, and has no centre line.

And there are other ways of bringing the 85th percentile speed into line with a 50km/h (or 30mph) limit on these kinds of distributor roads – for instance, pinch points for motor traffic (that don’t affect cycling).

So if the 85th percentile speed on a 30mph road near you is (under free flow conditions) closer to 40mph, that should tell us that action is needed to bring driver behaviour more closely into line with the posted limit, through these kinds of measures. Principally, perhaps, by reclaiming a good deal of the carriageway for cycling, consequently narrowing it down for motor traffic.

I hope this explains why I’ve changed my mind, and why the 85th percentile can be a constructive tool for improving streets for walking and cycling!

Entrenching car dependence with brand new development

A few months ago I commented on the new Waitrose/John Lewis retail site in Horsham, principally in relation to the way the visualisations of the (then yet to be opened) new development ducked the problematic issue of a very busy road severing the site from the town centre, but also on the potential difficulties of getting to the site by bike and on foot.

Now that the site is open, it is quite obvious that, yes, walking and cycling have been completely failed by the planning process. As I hope to explain here, cycling to Waitrose and John Lewis is effectively impossible, except for those who want to cycle (illegally) on footways, or for the tiny minority of people who are prepared to ‘negotiate’ with motor traffic on a dual carriageway carrying 20-25,000 vehicles per day.

To set the scene, here’s a video I’ve made showing the ‘legal’ cycling route to Waitrose.

To repeat some of the points made in the video – this isn’t an ‘out of town’ site, it is just outside the town centre, separated from it by the road I am cycling on. The route shown in the video is the one that will have to be taken by the vast majority of people who live in Horsham if they want to legally cycle to Waitrose – only a small proportion of the town’s population live in the ‘opposing’ direction, and they too will have to cycle on this dual carriageway, as this is the only access for the supermarket.

There is heavy traffic in the video which actually makes the experience of cycling to the store slightly less hostile, principally because of reduced vehicle speeds. At less busy times, moving out into the outside lane (as I do in the video) is much less easy because motor traffic will be travelling at or above 30mph.

The video also shows someone cycling on the footway, from the supermarket. This isn’t legal (and I don’t think it should be – the footways, as currently designed, are too narrow). But it is exceptionally common. People want to cycle to Waitrose, but faced with the choice between a four lane, high speed, high traffic road, and trundling on the pavement, people are unsurprisingly opting for the latter.

Not setting out to to break the law – just being failed by highway engineering

Cycling has been squeezed out on these kinds of roads for decades, and this new development has done nothing to address this root problem. The only silver lining on the cloud here is that, in undoubtedly attracting more ‘ordinary’ people on bikes to find their way along this road to the supermarket, the problem is now increasingly visible and less easy to ignore.

My video also shows the stupidity of planning entirely around motor traffic – from start to end of the video, my trip is only around 300m as the crow flies, but it takes me three minutes to cover this distance, in large part because to even get to the front door by bike (which is where people cycling should be going) I have to go out of my way to a roundabout, and then negotiate my way through two levels of a car park. There is no direct access to the front door by bike.

Some amazing open goals have also been missed here – whether by Waitrose themselves, or by council officers, or both.  Mainly, there are no access points into the site from the surrounding area, only the road I cycle on in the video. This is incredibly frustrating.

Standing in front of the main entrance, it is quite easy to see the main road to the north. The silver car is travelling along this road, and the white building is on the far side. It is a distance of only 80 metres or so from where I am standing.

But there is no walking (or cycling access from here – instead, you have to go take the long way round, the motor traffic route. I’ve marked this obvious (missing) connection on the visualisation of the site – the red line.

This is looking north, across the site, to the road running east-west (left-right). But there is no connection through to the west, either – a housing estate clearly visible, and a passage there to the side of the supermarket, but… fenced off.

This missing connection would run here – again, marked in red.

Again, the absence of this connection means a walk of a few metres is converted into one of several hundred.

Nor is there access at the south-west of the site. The development looms behind the housing here (circled) but again, no direct access, no connection with an existing path running along the river.

The overall impression is of a development that has been plonked down, with no thought or consideration, no attempt to connect it up sympathetically with the surrounding area, by foot or by bike.

The three missing connections described here, in red – with the only existing access (from the major road) marked in blue

Anyone living to the south, west, or north of this site has to go some distance out of their way to get to it. Combined with the hostility of the road you are forced to walk along, or cycle on, this development has entrenched, indeed worsened, car dependence within the town, which is pretty appalling given that this was a blank slate, in 2014.

The final insult – useless bike parking, which is (of course) placed as far away from the entrance as possible

Talking about ‘danger’, again

Some thoughts about ‘danger’ and ‘dangerising’ cycling had been floating around in my head, following recent local discussion about whether talking about ‘danger’ puts people off cycling, and whether we should refrain from talking about it all.

This issue has reappeared today, with some comments from Anna Glowinski in the Evening Standard (that may or may not have been accurately reported).

Speaking as she prepared to race today in a pop-up street velodrome in Broadgate, Glowinski told the Standard: “I think it can be quite damaging to talk about how ‘dangerous’ cycling is. I really don’t think it is that dangerous. The reason I think women are getting hit by lorries is because it’s an assertiveness thing. […]

“I think it’s good that cycle safety is taken seriously and highlighted so it’s high on the political agenda, and people care about road safety and think about how to make certain junctions safer,” Glowinski said. “But constant highlighting of cyclist accidents can be a bit misleading. I get told all the time: ‘You are taking your life in your own hands, you are crazy.’ It’s misleading. It’s putting people off.”

I’ve emphasised in bold the passages that I think exemplify the kinds of objections made by people who think we shouldn’t talk about ‘danger’. We’ve been here before, of course, and others have eloquently covered the same ground.

At face value Glowinski’s comments appear confused – on the one hand she thinks it’s good that safety is on the agenda, and that we are talking about how to make roads safer. But at the same time a ‘constant’ highlighting of these issues is a problem. Is it even possible or sensible to draw a line here? This leads me to believe she may have been selectively quoted, or was pushed for a quote on something she didn’t really consider.

But, more generally, I think an important distinction often gets missed here. It’s vital to stress that when people like me, who are interested in increasing cycling levels substantially in Britain, talk about danger – both in objective terms, and in the way perception of danger is a major barrier to cycling uptake – we are not arguing that cycling is an intrinsically dangerous mode of transport. We aren’t say that cycling itself is dangerous.

Instead, quite specifically, we are arguing that the design of certain roads and streets, and the nature of the motor traffic using them, presents an unacceptably high risk to people cycling on them. Cycling on a quiet residential street, with very low levels of motor traffic, is acceptably safe to anyone, but obviously very different from cycling around the Elephant and Castle, or Hyde Park Corner, or through Kings Cross, places where you have to make your way across multiple lanes of motor traffic travelling at higher speeds than you.

… Or through junctions where you are mixed with a high proportion of HGVs. Or sharing space with motor traffic travelling at the national speed limit on rural A-roads, or trunk roads.

Exposure to this kind of motor traffic is unacceptable. It continues to baffle me why, in a country that (quite rightly) takes Health and Safety very seriously, these risks continue to be tolerated. Certain kinds of step ladders have to be used in the workplace, yet it is apparently fine and dandy for local authorities to build new roads where people cycling are expected to mix with heavy traffic, travelling at speeds of 50 or 60mph, ‘negotiating’ their way into the middle of the road to get around roundabouts.

A new road in West Sussex. Cycle here.

The only way these roads even appear to be ‘safe’ is because next to no-one is using them on a bike. (Despite this, cycle KSIs on these kinds of roads form a considerable percentage of the total, even if the number of trips being made on them by bike is 1-2% of the total.)

The reasons so much of the British road network is dangerous for cycling are established reasons –

• speed differentials while sharing the same road space;
• major differences in mass while sharing the same road space;
• unforgiving road design;
• unpredictable or uncertain layouts;
• layouts that fail to account for human fallibility.

In short, all the attributes that are being designed out of Dutch roads and streets, thanks to Sustainable Safety.

Big differences in speed, mass and momentum means separation is a necessity.

Meanwhile Britain squeezes cycling onto roads that are simply not designed to accommodate it safely – with predictably tragic outcomes.

Does pointing this out really ‘put people off’ cycling? I think that’s a pretty far-fetched assertion. For one thing, we’ve been talking about road safety in general for decades in often quite vivid detail – in particular, car safety – without putting anyone off driving. And we have succeeded in greatly reduced the exposure drivers face while travelling around on roads and streets, by designing more forgiving environments for motoring, that tolerate minor mistakes, and reduce the seriousness of consequences when mistakes occur. (The problem is that cycling has largely been ignored in this process).

The implication of the ‘putting off’ claim, therefore, is that cycling is an especially fragile mode of transport, one that can collapse when people talk about the downsides of it; that exposure to risk and danger, and the perception of it, genuinely is a problem for cycling, compared to other modes of transport.

But even for the ‘putting off’ claim to stand up to scrutiny, there must exist some large cohort of the population that is willing to cycle on roads that have all the kinds of problems described here, yet will choose not do so simply because these problems are being talked about.

Is this really at all probable? Are they somehow blind to the hostility of these roads and the hazards they present, yet simultaneously so danger-sensitive that mere words will stop them cycling on them?¹

The general public might not be particularly au fait with the principles of safe road and street design for cycling, but those principles will correspond closely with what we as human beings can instinctively judge to be unsafe. Faster motor traffic whizzing past us at close proximity feels unsafe. Being surrounded by HGVs feels unsafe. Junctions which present multiple potential conflicts and uncertainty about what other parties might be doing feel unsafe. And so on. These are the reasons most people don’t want to cycle on Britain’s roads.

I think most human beings are pretty good at assessing risk for themselves; they might not get it right all the time, but they can judge that it is safe enough for their children to pedal around in a park, or on a small section of pedestrianised street that rarely carries any motor traffic…

… while at the same time judging that allowing their children to cycle on the road with HGVs at the junction just yards away, in the background of the same photograph, presents an unacceptable level of risk.

This is exactly the point that David Arditti makes in the post I have already linked to –

I think the advocates of cycling need to stop treating the public like idiots who cannot correctly judge what is or is not an unacceptably dangerous activity for them to engage in. I think they can judge.

The public knows that cycling itself isn’t dangerous. That’s why families will wobble around parks, and up and down trails, and in those places they feel comfortable. But they do know that cycling on certain types of road presents a kind of risk – even a feeling of risk – that they simply aren’t prepared to tolerate.

Talking about addressing those risks isn’t going to stop anyone from venturing onto those roads on a bike, who wasn’t already prepared to do so.

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^{1. [I am vaguely aware that statistics suggest there may have been a ‘dip’ in London cycling levels following the six fatalities in quick succession in late 2013; but this is surely attributable to the deaths themselves, rather than the people making the case for changing they way roads are designed to prevent these kinds of deaths from occurring in the future.]↩}

British ‘Simultaneous Green’ junctions, in… 1979?

I’m currently working my way through a DVD set of films from the BFI on cycling in Britain. One of these films is called ‘Free Wheeling’, which you can watch yourself on the BFI site (although it will cost you £1).

The film was produced for the Department for Transport in 1979, and appears to be aimed at councils and local authorities, showing them what can be currently be designed for cycling, based around Local Transport Note 1/78, Ways of Helping Cyclists in Built Up Areas, which we see, and is referred to, several times in the film.

It’s quite eye-opening – there are some things in there that were obviously radical at the time, like contraflow cycling on one way streets (something that, ridiculously, we still struggle to implement with any consistency 36 years later!).

What really caught my eye, however, was this short section on signalised junctions.

To my (untrained) eye, at least, this looks remarkably like, well, a simultaneous green junction – two of them.

In the first section of the clip, we see a man on a bike setting off from a bicycle-specific signal, heading diagonally across a junction, while other people cycling emerge from the road he is heading towards.

Note that there is apparently nothing to stop any of these of people choosing to cycle off into any of the exits they want to use.

And indeed this is precisely what happens – the man and the woman emerging from the junction opposite do head off in different directions, the woman ‘yielding’ to the man in the blue jumper.

As this occurs, the voiceover states

There are many variations [of this type of junction] possible, depending on local circumstances

which funnily enough is exactly what David Hembrow has been saying about ‘simultaneous green’ arrangements for cycling – that they can work at junctions of different sizes and shapes.

The second junction in the clip is even clearer. We see two people arriving at the junction, waiting at the corner on cycle-specific infrastructure, for a green signal to progress across the junction.

Note that this ‘corner’ arrangement is precisely the same as that at ‘simultaneous green’ junctions in the Netherlands.

Positioning on the corner allows people entering and exiting the junction to take the most direct route across it for the destination they want.

As the two cyclists get a green signal, all motor traffic at the junction is held.

As in the previous example, people cycling emerge from the opposite side of the junction – not directly opposite, but from a cycle track at 135° to their own entrance to the junction.

Note, again, that there is nothing to stop people choosing whichever exit they please. All these (conflicting) options are possible.

The final lovely detail is that there is an induction loop to detect people waiting at the junction; something commonplace in the Netherlands, but extraordinarily rare in Britain.

I’d love to know where these two junctions are – my guess, from the rest of the video, is somewhere in Peterborough – and indeed what happened to them, Do they still exist today?

UPDATE

An eagle-eyed Jitensha Oni has spotted that the second junction is indeed in Peterborough, near the railway station. It looks to have been replaced with a large roundabout, albeit with some pretty decent-looking grade-separated cycling provision.

As others have pointed out, these aren’t strictly simultaneous green, as while any exit can be chosen by people cycling, there are only two (opposed) entries to the junction at the same time. Still, I imagine this was pretty radical at the time, and still is now!