Saturday, 19 June 2021

The Curious Case of the Dutch-ish Roundabout of Drayton Park

I've scolded people for calling things Dutch or Dutch-style when they really aren't. I'll preemptively scold myself for mentioning Dutch-ish in the title of this post, because it's not really about a Dutch-ish roundabout.

To be fair to the London Borough of Islington, it has stayed well away from the Dutchification rhetoric and has developed and constructed a perfectly reasonable "continental-style" junction. In other words, a roundabout with compact and tight geometry which requires drivers to slow down in order to go around it. It just so happens that they've popped parallel zebra crossings on each of the arms which hints at the Dutch urban roundabout approach (and I'll explain the differences in a bit).

The roundabout is at the junction of Drayton Park and Benwell Road, the latter of which has been filtered to keep through traffic on main roads such as the parallel A1 Holloway Road. The junction forms part of Cycleway 38 which is under construction between Finsbury Park in the north and Highbury Fields in the south. It also links to an existing cycle crossing of the A1 Hollway Road between Fieldway Crescent and Madras Place and so creates some useful cycling connections.


Above is a general arrangement drawing from the London Borough of Islington which shows cycle tracks around the roundabout with the parallel zebra crossings. Benwell Road is about 340 metres long with the Arsenal football stadium at its northern end. With the current filtering scheme, the roundabout provides an easy way to access the stadium by cycle from Highbury Fields.


The scheme was originally agreed in October 2019 and was completed in the last few weeks. There has been some overlap with experimental filters in the wider area and so traffic levels and patterns are probably different to what they might have otherwise had been. The above image shows the  "before" layout to the north of the junction looking south with the "after" in the photograph below;


In terms of the components, let's start with the arrangement for general traffic. There are three arms and each one has one lane in and one lane out of the roundabout. The directions are separated with triangular splitter islands. The circulatory area comprises a general running lane, an overrun area constructed from block paving and a raised circular island (below).


What isn't east to see is that the carriageway of the circulatory area falls out to the edge to create an adverse camber, a feature which helps to act as a driver speed-reducing device which you can just work out by the tilt of the vans in the photograph above (it also makes drainage design easy). There isn't any turn left or chevron signs on the roundabout, probably to keep clutter down and because the layout is so very obvious. I think I would like to see some large planting or other landscaping on the island to reduce the views drivers have across the junction which would also help with speed reduction.

It's a very nice example of a compact or continental roundabout, an example of which is given on Figure 10.45 of LTN 1/20; and in low traffic and low speed situations, many people would feel entirely comfortable cycling with traffic. However, notwithstanding local filtering changes, Drayton Park at least is still going to be fairly busy feeding the side streets and so the roundabout usefully protects most people.


There is an orbital carriageway level cycle track around the roundabout which is separated from the carriageway by skinny traffic islands, roughly 600mm wide. For a Dutch urban roundabout, the cycle track would generally have a 5 metre buffer which you can read about here and people would be joining the crossings at 90° rather than having to turn through 90° as they cross. 

Right turns for cycle traffic require the use of the parallel zebra crossings which can be both awkward in terms of having to check nearly behind you and having a very tight turning space because of the skinny island (below). 

You'll see in the film linked to at the end of this post that I was taking a pretty curved path across the cycle side of the crossings to reduce the tight turn at the start and end of the crossing. This is going to be quite awkward for people using non-standard or adapted cycles. I would have liked to have seen the planting and cycle track swapped on this arm so that there was more turning space and so people cycling don't need to look behind them.


The left turns (or ahead for the southbound Drayton Park movement) are "free" and fully protected from traffic (below) which means no loss of momentum. If someone is about to cross the zebra crossing, then speed can easily be adjusted.


The slowing of traffic through the roundabout and the slowing of right turning cycle traffic does lower the collision risk and with the parallel zebra crossings, drivers should be expecting to stop anyway. There is space for drivers to stop before the crossing (below) and I doubt blocking back will be much of an issue because the crossing points are set back.


To the north of the junction, there are one-way cycle tracks currently being constructed which will extend protection to Martineau Road (and another access into Arsenal) and then northbound (uphill) protection a little further.


So, is the roundabout good? Largely yes, but even though lots is squeezed in, I would have preferred wider buffers with the carriageway so right turns were gentler - in some cases, the planting and the cycle track could have been swapped. The junction could have been left as a T-junction with a squarish cycle track layout and parallel crossings, but I think the use of the compact roundabout is clever because it's pretty good at getting driver speeds down and that does make a difference. I'll leave you this week with a little film of the junction with a passing note to this is my 450th blog post!


Saturday, 12 June 2021

Old Bethnal Green Road: Filtered Permeability Goes Large

Last summer, I had a mooch around the Tower Hamlets - Hackney border looking at some neighbourhood schemes. Well, this week I am back for another look at the Old Bethnal Road project which has been recently completed.

I've seen this scheme on Twitter a fair bit, but as ever, I like to make my own visits to see things in the flesh as well as to get a sense of how something "feels" which is very important as a designer.

The Old Bethnal Green Road scheme is part of a much wider "Liveable Streets" project developed by the London Borough of Tower Hamlets. At it's simplest, the project is just a piece of modal filtering, but it fits within a wider jigsaw of pushing through traffic back onto main roads. 

As usual, there is controversy with some people unhappy that they can no longer drive through and have to use the local A-road network. Anyone posting praise for the scheme on Twitter is immediately challenged or sometimes abused. We should acknowledge that roads like the A107 Cambridge Heath Road and the A1209 Bethnal Green Road have issues of congestion and air quality, but we should also recognise that they are better designed and managed for longer distance traffic. 

We should also recognise that we need to change our streets and that endless debate never gets us started. We're always told that whichever scheme is promoted is the wrong one, it's the wrong street, there's something else going on which is more important and so on. Tower Hamlets has decided to start making strategic changes which have emerged from a great deal of local engagement and co-design.

The scheme itself runs between Mansford Street and Clarkson Street, and essentially allows Middleton Green to extend into the street at the eastern end of the scheme which is a large filter between Clarkson Street and Temple Street.


The photograph above shows the layout by Middleton Green. The carriageway has been replaced by a pair of one-way cycle tracks and a central open space with trees and seating. 


The choice of a pair of cycle tracks is slightly curious and so we need to look at the network to see why. The western end of the scheme makes Old Bethnal Green Road one-way eastbound and contiguous with Temple Street which is one-way north. In both cases, cycling is allowed in two directions and at the point where Old Bethnal Green Road becomes Temple Street, cycle traffic is protected with a cycle track. Above is the view on Temple Street looking south.


The photograph above is looking east along Old Bethnal Green Road with Temple Street to the left and the eastbound cycle track ahead. The sketch below shows the general layout with the cycle tracks hatched in.


Of course, there could have been a single two-way cycle track which I have sketched below. This would have maximised the space contiguous with Middleton Green and maybe would have been an easier route to keep clear for emergency access, but as it stands, the layout does flow well for east - west cycle movements.


There could also have been a scheme without cycle tracks, but having something marked clearly does help with legibility. The cycle tracks are at footway level which might be an issue for some visually impaired people, although I would tend to say that this is a pedestrianised area through which people are allowed to cycle and materials have been used to guide people cycling into an appropriate place, although the give way triangles at the western end are overkill (below)


There is one problem with the layout, however. There is no way for people to cycle west and then turn north into Temple Street. My two-way cycle track option would make that a simple right turn onto the northbound general traffic route for Temple Street, but the scheme as built hasn't made any provision. I've added in green what should have been included in the current scheme (below).


As well as the hard landscaping, new planting has been added with trees and rain gardens (below). It is a completely changed place.


To the west of the new open space, the westbound cycle track is buffered with planting where there is space (below). 


Eventually, the cycle track runs next to the oncoming general lane. At Manford Street (below), drivers emerging from the side roads can turn left or right as the general traffic running lane switches to westbound with a mandatory contraflow cycle lane for eastbound cycle traffic which is part of the local system to remove through traffic (below). The end of the westbound cycle track does drop to carriageway level with jolt and that needs sorting out.


Aside from my concern about the absence of the right turn for cycles from Old Bethnal Green Road into Temple Street, the project is otherwise excellent. You don't need to take my word for it, in the 20 minutes or so I spent nosing around, there were a couple of people sat on the chairs in the public space while people cycled through every few minutes (below).


Securing the space could have been achieved with a line of bollards at each end, and at the eastern end, there is such a line to prevent anyone from driving through, other than emergency vehicles. However, I think with any scheme to remove through traffic from an area, there needs to be something "given back" through how the new space is managed. 

There will be some people in the area aggrieved by the fact that they need to drive a bit further (depending on their journey) which will be seen as a loss. The provision of new open space may not be immediately something they see as a gain personally, but in time the space as an anchor for a quiet neighbourhood might reduce the feeling of loss and they might even change their minds.


Despite the cycle tracks, this is not a cycling scheme, but people in the area now have a decent east-west option over Hackney Road and Bethnal Green Road. There's also the Oaklands Secondary school to the western end of the scheme which now a little easier to cycle to. I'll leave you this week with a short film of the scheme.


Saturday, 5 June 2021

In Search Of The Diagonal Divider

The "Diagonal Divider" is a relatively rare beast, but if you search carefully enough, you can find some interesting examples. Thanks to a little bit of crowdsourcing on Twitter, I've managed to collect a few more examples for my collection which I recently visited by cycle.

OK, many people won't have a clue what I am on about (settle down), so let's start with a little more information. A diagonal divider is a type of modal filter which uses the space within a crossroads to create a pair of opposing bends for motor traffic. For those that don't know, a modal filter is a point or section of street through which different classes of traffic are filtered out. This usually means motor traffic, but filters can be designed to permit certain classes such as emergency services vehicles.

Diagonal dividers are methods of filtering which can be see all over the world and they are a feature found in the excellent NACTO Global Street Design Guide from which I reproduce this nice little graphic;


As you can see, the general approach is to use one of the diagonals to "break" the general traffic grid while still leaving things completely permeable for walking and cycling.

Of course, with NACTO being a US organisation this might give a little insight on the use of diagonal dividers given how many cities have streets set out on grids. There's an interesting graphic in the 1981 Federal Highway Administration report "Improving The Residential Street Environment" (Figure 3);


The report was written by Daniel T. Smith Jr and Donald Appleyard, the latter of which some readers will know as being a giant in liveable street design and research in the 1960s and 1970s - it's a similar diagram to that in his more famous (and hard to get hold of) work "Livable Streets". In this case, Smith & Appleyard call the features "diagonal diverters". As is often the case, we are looking at something which has decades-old thinking behind it.

Building streets on grids is a really space efficient layout and it's thinking which can be found in the contemporary UK "Manual for Streets" where there was interest in the efficient use of space with layouts and junction design stemming from it. 

Permeable streets are fantastic for walking and cycling, but they can suffer from rat-running, high driver speeds (where roads are straight) and collision risk at the crossroads. Smith & Appleyard use diagonal dividers in three layouts in Improving The Residential Street Environment (below).


My favourite of the three layouts is Figure 12: Return Loops, where drivers end up back on the street they accessed the area from. Anyway, let's head back to the UK (well London at least).


Above is the junction of Barclay Road and Mornington Road, Waltham Forest. The photograph is taken from the east side of the junction, looking west. I'm standing on Barclay Road and general traffic is one-way going away from me and turning right. On the left is Mornington Road and general traffic comes from the left and turns left into the distance. There is a lockable bollard in the centre for emergency access. A different angle of the diagonal divider is shown below.


Cycle traffic is permitted in all directions which means that there is a local network which completely permeable, whereas drivers have to take a longer route, but have full access to each location. The arrangement gives an opportunity to add planting to the street.


Two kilometres west is the junction of Capworth Street and Vicarage Road (above) which is has less landscaping. Again, the streets are one-way for general traffic and 2-way for cycling. Although there is less landscaping on the divider itself, the council has taken the opportunity to add some near the bend where car parking isn't permitted (below).


The use of diagonal dividers is often associated with developing a network of one-way streets for general traffic. This works well with dividers because in general, vehicles need more space when turning (because of the way steering geometry works) and dividers squeeze space on what becomes a pair of tight bends. Of course, if the streets are quiet, then the risk of vehicles needing to pass each other is reduced to a point where it doesn't have to be an issue and so below is the junction of Skipworth Road and Primrose Square in Hackney;


The give way markings are not because of the tight bend, but as a way of trying to prioritise cycle traffic running left - right on the photograph above (north - south through the junction) which is part of a local cycle route. I'm in two minds about the give ways because they don't guarantee that drivers will slow down and look.


The photograph above is the junction of Ronalds Road and Avron Road, Islington. This layout has both streets being 2-way for all traffic, although there is a wider traffic control strategy at play which means that the streets are only of use for people driving with business in the area. This filter as a twin just down the road at the junction of Ronalds Road and Horsell Road (below);


This filter has a much wider access point which allows some general traffic (coming towards us and then turning left) as part of local changes to traffic management as for the construction of Cycleway 38, although this is different to the original proposals because of other filtering works in the area. The layout does also give more emergency access to the area, but it will require camera enforcement to ensure compliance.


Camera enforcement is becoming more widespread in London such as a the junction of Frampton Park Road and Loddiges Road in Hackney which had a makeover with public realm and planting improvements a couple of years ago, but more recently has had lockable bollards removed in favour of camera enforcement. 

Personally, I think cameras should be used in very special circumstances, but I think the bollards were being continually removed so I can understand the change. In the long term, motor traffic levels need to come down and so this should hopefully allow filters to be redesigned to be full motor traffic closures because emergency vehicles won't be held up on main roads.

For me, one of the main advantages to using diagonal dividers is that the local traffic can access the area without having to resort to three-point turns or reversing movements. This is especially important where refuse or servicing takes place because reversing vehicles adds safety risk to other highway users. They are also good driver speed-reducing devices and they can reduce conflicts at existing crossroads.

The main disadvantage is that where point filters create almost zero motorised traffic either side which is great for giving space back to the community (especially children) dividers don't generally give such space and they still have traffic passing by which is less conducive to street activity near the filter. While there will be opportunities for planting and landscaping, they just don't release public space in the same way.


Above is the junction of Worship Street and Curtain Road which is on the Hackney/ City of London border. The public realm works give the impression of a nice public square, but in reality, the streets on both sides of the filter are busy. The City of London side runs one-way for general traffic between Appold Street and Worship Street to such a level (including buses), cycling requires protection in the contraflow direction by traffic islands on each side to stop drivers cutting the corner;


The Hackney side of the divider is two-way for general traffic, a fair bit of which is providing servicing in the local area. The bollards of the divider are timber and with air gaps up just under 1 metre, they are simply unhelpfully arranged for cycling permeability. As a concept, I would be wary about selling dividers as a way to create public space unless the junction being treated was very large and substantial space was being released.

One of the issues I saw with some of the examples was that walking hasn't been properly considered, but this is also an issue with many junctions generally. In order to make our divided crossroads fully accessible, we need four pairs of dropped kerbs to accommodate all of the desire lines. 

Usually, we only tend to provide dropped kerbs across the side roads of a crossroads which is pretty motorcentric thinking anyway because we don't move past the desire lines of drivers. It is one of the issues that experimental schemes have not always addressed in terms of either not having all of the dropped kerbs needed, or the use of planters which have blocked existing dropped kerbs.


Dropped kerbs provided to accommodate all desire lines (yellow)

Diagonal dividers are a great component to have in our low traffic toolbox because they allow general access traffic to move around a neighbourhood in loops while keeping maximum cycling permeability if done correctly (and we are trying to make cycling easier than driving). But care is needed around whether to have 2-way general traffic, the carriageway width at the tight bends created, cycle safety through the features in terms of interaction with general traffic and that pedestrians are properly supported in walking through.

Sunday, 30 May 2021

What Is A Dutch Style Roundabout?

Look, I don't want to be that guy, but when I see a UK cycling scheme trumpeting a "Dutch-style" roundabout, it's going to get my attention and I'm going to give it a closer look.

North Tyneside Council is currently consulting on a raft of cycling schemes which are being delivered over the next couple of years using funding from the UK Government's Active Travel Fund (ATF) and the Transforming Cities Fund (TCF). The former is essentially part of the response to Covid where 2020/21's fund was more about pop-up and interim active travel works with 2021/22 being about making things permanent or extending them. The latter closed to applications in 2018 and is about investing in public and sustainable transport in city regions. Both funds are for England only.

The principal problems with the funding are that they are part of the long stop-start tradition with bidding that has made delivering cycling (and walking) infrastructure difficult to plan for. Inevitably, local authorities don;t have certainly in building their own capacity and so lots of projects are delivered using consultants' help (and there I declare a general interest), rather than being able to deliver the core themselves.

I thought it important to set some context here because the fact is that North Tyneside is actually trying to create a better cycling network which is head and shoulders above many English authorities. The council says that it has £1.6m ATF funding and £7m TCF funding, although the ATF money is time-limited to March 2022 (another Government-imposed deadline). Have a look at the plans yourselves and I would encourage locals to respond. For this post, I am going to concentrate on the aspect that caught my eye.

The roundabout in question is on the A191 Rake Lane and forms a junction with Billy Mill Lane and Brookland Terrace (In the consultation it is called the Rake Lane Roundabout). The A191 and Billy Mill Lane are large single carriageways with little frontage development (there are parallel streets operating like service roads). This roundabout is part way along wider plans for the A191 corridor between the New York Road roundabout in the west and the Preston Road North roundabout to the east. 

The general treatment for the A191 is to reduce the speed limit to 40mph west of the Rake Lane Roundabout (New York Way) and then provide cycle lanes on the carriageway with wand or orca protection. To the east of the roundabout the speed limit is already 30mph, but the same lanes with wands/ orcas are proposed (there is already an eastbound advisory cycle lane). The cycle lanes pass in front of bus stops and there are also long gaps in the protection at junctions.

There are also parallel zebra crossings proposed (generally where refuges are removed) and a couple provide access to the North Tyneside General Hospital which is a good place to serve. Unfortunately, the westbound cycle lane gives up at the hospital entrance (below).


From the plans at least, the cycle lanes appear to be advisory which is immediately an issue because drivers are allowed in them from time to time - this is in direct conflict with putting in the light protection. These should be mandatory lanes. But it's academic because the A191 looks pretty much terrifying for most people and I really can't see how paint and a few wands or orcas will make people fee safe. This is especially true of New York Way which will have a 40mph speed limit (below).


New York Way is about 10m (maybe a touch narrower). If the minimum cycle lane width of 2m is provided (6.4.2 in LTN1/20), that leaves traffic lanes of 3m which are not appropriate on a 40mph road like this. I suspect these lanes will be 1.5m which will feel very exposed. The road also has little frontage access and so I wonder who will be using it, especially as the light protection ends at the west end.


Figure 4.1 from LTN1/20 (above) is useful in this context. For a 40mph limit with cycle lanes, we get a pink box which states;

"Provision suitable for few people and will exclude most potential users and/ or have safety concerns"

Light segregation gets us into the amber area which states;

"Provision not suitable for all people and will exclude some potential users and/ or have safety concerns"

For my mind, the distance between wands/ orcas on the plans isn't particularly dense and I simply cannot see how most people would be reassured. I wouldn't cycle on New York Way full stop.

For the eastern side of the corridor, we can use the same figure to look at what happens with a 30mph limit. For light segregation at all traffic flows we are into the green, but again, I would still have concerns about the level of protection provided. This is an A-road corridor with a character that is not built up and urban; it is suburban fringe and this shouts cycle tracks to me. Some sections have the service road which could be properly filtered as a kind of cycle street too.

OK, that's a fair bit to talk about before getting to the roundabout design, but the wider network context needed to be considered. The roundabout itself is is very large at around 75 metres diameter (it's a bit oval) to the carriageway edge of the circulatory area. There are two wide traffic lanes around it and each of the 4 entry roads are single carriageways which splay out to 2-lane entries. The exits are single lane, but very wide and the arrangement means that drivers are able to drive quickly into and out of the roundabout. 

The roundabout dates back from the end of the 1960's/ early 1970's. Looking at Old Maps you can see Billy Mill Lane being widened and straightened on the 1966/69 OS map and by the 1971/77 OS map, the roundabout exists. You can look around to see housing development in the general area from the early 1950s through to the 1970s - a growing suburbia with road building - it seems nothing changes.

For the cycling scheme, there are two proposals for the roundabout. I'll look at Option 2 first;


This option has mandatory cycle lanes on the two Rake Lane approaches and the Billy Mill Lane approach (which of course makes more sense that the advisory lanes on the wider plans). Brookland Terrace has advisory lanes. In all cases, the cycle lanes end at the roundabout entrances.

Each arm receives parallel zebra crossings. Brookland Terrance is single stage and the others are 2-stage given the wide islands which makes sense. The centre of the circulatory area is hatched, although the single traffic lane is still wide. The existing kerb lines appear to be retained, but the cycle lanes entering the roundabout and some other hatching means there are single traffic lane entrances and exits.

For people cycling through the junction, they can either stay on the road to mix with traffic or somehow get to the shared-use areas at the zebra crossings (I assume by a dropped kerb which is accessed sideways) and navigate via 2-way cycle tracks. Because of the shared-use areas by the crossings, there is lots of tactile paving to contend with.

2-way cycle tracks in the context of a very large roundabout actually makes some sense. For example, turning right from Billy Mill Lane means you can cycle anti-clockwise around the junction via 4 parallel crossings at a distance of about 120 metres. If you did the same in a clockwise fashion, this would be much twice the distance using 3 crossings. 

Essentially the design adds cycle tracks to the existing footways around the junction and adds parallel zebra crossings. But, it is classic dual provision for the "confident" and "cautious" cyclists when we should be designing for all (or at least 95% of people). The fact that people have to use cycle lanes (even with light protection) is probably still the reason that most people won't use the new infrastructure.

Option 1 is the headline grabbing "Dutch Style" roundabout which I'll look at in a minute, but first the arrangement;


With this option, the main cycling principle is a one-way orbital cycle track (clockwise) which is created from the outer part of the circulatory area of the roundabout, separated by "flexible surface islands" according to the plan. I don't know what this means, but I assume some sort of bolt-down product.

All of the arms have 2-stage parallel zebra crossings and single traffic lane entries and exits. This is good because people cycling (and walking) only have to deal with one traffic lane at a time and drivers don;t have to worry about what is happening on the other crossing as much as they would with a single stage crossing. This is a good design principle.

The triangular "splitter" islands for each arm have been narrrowed a little and they will extend into what was the outer part of the circulatory area to create a narrower traffic lane on the roundabout and protection for people cycling. Pushing general traffic towards the centre is better than the other design of pushing it to the outer edge simply because it tightens the turn drivers have to make, but it is still about a 70m diameter give or take which really isn't going to slow drivers that much.


Looking closer at the layout (Brookland Terrace and the eastern arm of Rake Lane in this case), we can see how new splitter islands have been added which provide buffer for cycle traffic from general traffic on the entry and exit points as well as giving decent pedestrian islands between the cycle tracks and traffic lane crossings. One point to mention here is that parallel zebra crossings should have the zebra stripes and elephant feet (for the cycle size) 400mm apart. This is a stupid rule in the Traffic Signs Regulations & General Directions 2016 which technically stops us curving the cycle part of the crossing. The zebra strips are also wrong as they need to be complete rectangular blocks, but I'll put that down to a drafting error.

The problem with this layout, however, are threefold. First, people cycling and wanting to cross the parallel zebra will need to almost look behind them (more than 90° in any case) for drivers leaving the roundabout which I have shown with green arrows (above) for cyclists and purple arrows for drivers. The crossing of traffic joining the roundabout is not a particular issue because speeds will be lower. 

Second is that drivers will be able to enter the roundabout at speed as shown by the orange arrow. If they can see a gap in traffic, this means the entry speeds are high and with the alignment the exit speeds will be high. As you can see, there is a set back of the cycle crossing from the edge of the roundabout which can fit a car, but it's not enough stopping space at any real speed and so creates shunt risk from traffic on the roundabout.

This is the nub. On the whole, Dutch roundabouts which include people walking and cycling are compact. In the CROW Design Manual for Bicycle Traffic, an urban roundabout would have a diameter of between 25 metres and 40 metres (across the circulatory area) to ensure driver speeds are kept low. With a diameter of maybe 70 metres for the "Dutch Style" roundabout, there is no way that the size is remotely Dutch and in fact, the island at 55m diameter would easily contain most of a Dutch roundabout!


The traffic entries to the roundabout should be perpendicular to the circulatory area and the cycle track should be orbital (and preferably one way) with a Dutch urban roundabout; there isn't a flaring as such, just a radius between the entry lane and circulatory area (above). This means that drivers have to actually use their steering wheels to enter and exit and cyclists cross perpendicularly reducing the need to try and look behind oneself. With the Rake Lane scheme, the cycle track is not orbital, it is more like the rural option which I'll show you in a minute.

The cycle crossing is set back 5 metres which isn't an issue on a compact roundabout as drivers are moving slowly with shunt risk reduced. The crossings are single traffic lanes at a time with a refuge between the two crossings.


The photograph above is the Frederik Hendrikbuurt Roundabout in Amsterdam. It's unusual as it has a tram line running through the centre where everyone gets held by a red traffic signal, but apart from that it operates as an urban Dutch roundabout. you can see the orbital cycle track, the set back to give drivers a stopping place (and space to enter the roundabout - things being broken down by task).


We could also look at the Dutch rural roundabout where people cycling (and walking - it would be a shared-use path) give way to traffic. In this case, there is still tight geometry for traffic, but the crossing points are set much further back to give drivers more space in which to stop if someone crossing misjudges the gap. There is the same perpendicular approach for drivers; no triangular splitter islands making it easier to enter and exit. There is less need to make the cycle track one way and in many cases, there are only cycle tracks around part of the roundabout in any case.


The cycle track is not orbital, it follows the general junction shape which means that cyclists have to slow down and then turn before crossing (above). This does lead to energy losses for the cyclist, but the geometry stops people just continuing across the road as they would do with the parallel zebras of the urban example. 


You'll also see the carriageway drain to the outside which creates an adverse camber (above) which slows drivers down along with an overrun area for large vehicles which keeps space tight for smaller vehicles avoiding the overrun. This will often be the same in urban areas, it's just easier to see in rural examples.

One piece of information I don't have is the traffic flow through the roundabout. The Dutch designs allow for up to 25,000 PCU (passenger car units) a day for single lane entry. The Dutch do use multiple lane entries, but despite there being examples which include cycling, they are much less safe and should be avoided. For UK roundabouts, the geometry which allows higher entry and exit speeds mean we can push more traffic through.

So, does it matter that this scheme is being headlined as a Dutch-style roundabout? In my view, yes. "Style" is doing some very heavy lifting. In fact the only facet of the design which is Dutch is the parallel crossings with single lane entries/ exits configuration, however, without all of the other details it can never be Dutch-style. In fact the only Dutch-style roundabout is in Cambridge which has cycle priority, but also the safety features required to be called Dutch-style.

So what would I do? Well, Given the context, I don't think I would be proposing an urban Dutch design, I would go for the rural example simply because this location is not in an urban location. Assuming I wasn't allowed to dig up the central island because of cost or the trees there, I wouldn't be calling my layout Dutch-style, but I would redesign the approaches to provide rectangular splitter islands (maybe 3 or 4 metres wide) to get the perpendicular approaches for drivers. 

The crossing points would be set back at least 10 metres from the circulatory area, but I would keep the idea of pushing traffic to the inside of the circulatory area with as narrow a traffic lanes as I could get away with, but which is still compatible with HGVs. I think I would also make the cycle track 2-way because with traffic priority, it would be much safer than a 2-way track and zebra. Having it 2-way also helps is provide a 2-way cycle track on New York Way, rather than the scary lightly protected lanes.

Above is a quick sketch to the same scale to show what I mean. To the east is New York Way where I've provided a 3.5m shared-use path with a 2 metre buffer from traffic. The crossing point is set 12 metres from the edge of the circulatory area and traffic is pushed to the inside. you'll note the perpendicular approach which helps slows driver speed into and out of the roundabout. There are lots of options for the other arms. If walking and cycling numbers are expected to reach any significant numbers, then we can provide separate space, but the 2-way nature of the layout allows people to choose the quickest option for them.

My sketch is not "Dutch-style", but it does follow sustainable safety principles where we control traffic speeds and where we don't expect people to cross more than one traffic lane at a time. I think the layout better fits the local road hierarchy and while I understand the desire to provide walking and cycling priority, I am not convinced it is the safest option in the local circumstances.

Saturday, 22 May 2021

The Five Principles

Earlier this week I gave a talk to Cyclox about what I thought made good cycle routes. The talk covered the five principles for cycling infrastructure with a round up on Low Traffic Neighbourhoods.

Now, I have covered LTNs many times in this blog and so this week I thought it might be interesting to talk about the five principles. I am a fan of the details, but a little step back to look at principles is always a good idea as it helps us understand how things fit together. This post is essentially the long-hand version of the slides I used in my talk which you can watch here.

The five principles crop up in all sorts of UK cycling planning and design policy and guidance - even in the most dire of the genre! It is no surprise that they pop up in the new English design guidance, LTN1/20 Cycle Infrastructure Design, and they are covered in some detail in Chapter 4. It's also worth stating that in fact they equally apply to planning and designing for walking. The reason for this is that these principles major on the human experience of self-propelled travel.


I was probably vaguely aware of them in recent years, but it wasn't until I got myself of a copy of the Dutch "Design Manual for Bicycle Traffic" (often called the CROW manual - above) that I really started to understand how this all fits together. It also pushed me to imagine network level design being as important (possibly more important) than route design. In other words, a problem issue on a cycle route may be more easily addressed by looking at what is happening at the network level - something I talked about in by post about Lea Bridge Road in Waltham Forest where separate walking, motoring and cycling networks have been considered (below), it's just that they are on the same route for Lea Bridge Road itself.


The five principles are as follows;
  • Coherence (Dutch use Cohesion)
  • Directness
  • Safety
  • Comfort
  • Attractiveness
The CROW manual states;

In general it holds that if the minimum level cannot (or can no longer) be met for one (or more) of the five main requirements, then the infrastructure will need to be modified.

This is where we discuss what a compromise might look like, but first, we need to have a look at the five principles. The CROW Manual uses them first to define what a main cycling network should be (maybe over a 300m - 500m grid in urban areas), but as we will see, they can apply at both the macro and micro level.

LTN1/20 reminds us that accessibility should also flow through the five principles. Whilst that is absolutely true and a good thing to point out, accessibility should be implicit and integral to planning and design.

Coherence - the cycling infrastructure forms a coherent whole and links all origins and destinations.
People travel because they have certain needs to satisfy. It's obvious when you think about it, but so much cycling provision in the UK has been developed in such a way as to tuck cycling out of the way as a problem to be managed, rather than a mode to be embraced.

People need to get to work, go shopping, drop the kids off at school (or get to school themselves), get to a GP appointment or provide care assistance to others. They also want to travel for leisure or entertainment or maybe they just want to get out in the fresh air. Those reasons for travelling therefore make it an absolute requirement to be able to get from home to all of these destinations, or to link trips together. This means that we are going to have to make many roads and streets useful for cycling.


However, the cycling network is going to be different to the motoring network and the class of road or street shouldn't really matter, we need to be providing a seamless experience. 

Grove Road in Stratford (above) takes cycle traffic from the side road onto a main road. The side road has people cycling on the carriageway and the main road has a cycle track. The transition is pretty seamless because it forms a coherent route. People can cycle from quieter side streets onto a main road which features the places people want to get to. 

This includes integration with other transport modes, because people sometimes need to use more that one mode for longer trips. The S-Train in Copenhagen (below) has cycle carriages to help suburban dwellers to cycle to their local station and then around the city. The Dutch have integrated their rail system with cycle hire which allows people to conduct their destination business before dropping the cycle back at the station.


Gaps in a network reduce coherence. In a situation where cycling is well-developed, it's not a huge problem, but where small numbers of routes are relied on, then gaps can be fundamental fails in provision. One of the implications is that barriers need to be tackled such as crossing large highways, railways and watercourses.

This extends to planned and unplanned events. A well-developed network is far more resilient than a single route because it gives options.


Above is a closure for utility works on the CS2 route in Central London. There is little parallel or network provision in the area and such a closure both ruins coherence, might discourage people from cycling in the future and some people simply cannot dismount and use the footway.

Directness - the cycling infrastructure always offers the cyclist as direct a route as possible (detours kept to a minimum).
Cycling (and walking) is about people getting around under their own steam. Sometimes people have a little assistance and sometimes they need more assistance, but they are moving around their worlds at a human scale which is an entirely different proposition to travelling by motor vehicle.


Directness is about minimising the distance or time people need to travel and so can apply at both the macro and micro levels. Cycling absolutely needs to be quicker (in time rather than absolute point speed) than the car for it to be competitive and the way we design streets fundamentally affects this. 

Judd Street in Camden (above) is filtered at Euston Road which provides a direct access across to Midland Road and a pair of cycle tracks. The estate behind the filter is pretty quiet with motor traffic having to take routes on main roads. so the local cycling network is direct in the general area and specifically through the junction.


Contrast this with the A12 Colchester Road in Romford where walking and cycling share tight space and have to use a staggered toucan crossing. There is no wider network and so people are forced through an indirect route through this junction in both space and time. Of course, it's entirely possible that a slightly longer route avoiding a large junction might be longer in distance, but shorter in time. It's also worth remembering that traffic signals are a product of motorisation.

There is guidance on what is an acceptable diversion which might range from 10% to 25% extra distance compared with driving, but I would caution the application of this because it's easy to end up designing routes which are slower cycling than driving.

Attractiveness - the cycling infrastructure has been designed and fitted in with its surroundings in such a way that it is appealing or attractive.
This is probably the most subjective and difficult to define of the principles, but it is still very important. Take a look at Adinda-Flemmich-Straße, Freiburg im Breisgau, Germany (below). This is a street in the Vauban neighbourhood which is famously low traffic.


I would suggest that most people looking at this street would say it is attractive, but working out why might be a little more subjective. However, the attractiveness has been designed in from the start. The low traffic nature of the street is obvious and the designation as a "home zone" can pretty much be ignored. 

There are some nice materials on the street which don't dominate the scene. There is also lush planting which is nice to look at as well as changing the visual nature of the street to the few drivers needing access. The street is also given a sense of enclosure by the scale of buildings to give pleasing proportionality to the street. It's a place to cycle, but it is not cycling infrastructure as such, but the surroundings are appealing.


A smooth asphalt surface is attractive (above). I don't mean the colour, I mean the fact that there is no vibration imparted to the rider as they move (although colour can be part of the puzzle which makes something attractive through the "look and feel" of a place). Vibration is an assault on the senses and it detracts from the sights and sounds of the immediate world.

Attractiveness extends to having legible junctions which allows someone to make decisions before the decision point so that their experience is flowing. As soon as things become disjointed or confusing, navigation starts to become an irritation. It's also worth noting that attractiveness extends to the end of the journey. Can one cycle up (or into) the destination to park or does one have to search for a place to park which wastes valuable time?


Attractiveness is about escaping monotony. Cycling somewhere which has life (and can be lively), where there are things to look at be it the landscape or architecture. Personally, there are some post-industrial areas in my part of London which are interesting, if not aesthetically attractive. Marine Parade in Great Yarmouth (above) has a wonderful cycle track which has plenty of interest which draws one's mind away from thinking about the mechanics of cycling into what's going on in the immediate environment.

Safety - The cycling infrastructure guarantees the road safety and health of cyclists and other road users.
Safety is both objective with collision risk, designing out interactions with fast or heavy traffic and it is subjective in terms of how safe something feels both day and night (also called social safety).


Cedar Road in Romford (above) was filtered as an experiment. It runs parallel to the A12 and was used as a rat run by people trying to avoid traffic signals on the main road. At the time of the experiment, there were 1,920 vehicles a day using the street which dropped to 403 after filtering.

The street has parking on both sides and from a cycling point of view, having to face off with drivers who's attention was on beating the A12 was subjectively unsafe. In addition, having fewer vehicle interactions has improved the objective safety. The street now feels perfectly safe to cycle along without any protection and pollution exposure is far less than it would be cycling along the side of the A12. 


Safety is also about the details and not providing layouts which create risk to people cycling. The photo above is a cycle track at Main Road in Romford where a forgiving kerb has been provided which won't throw someone off if it is clipped and it won't catch pedals either.

Junctions are the highest risk in a traffic system because it's where different modes interact or end up in conflict. Good design helps us ensure that junctions are legible so that everyone understands the behaviours expected of them when passing through.


The roundabout on Provincialeweg, Vogelwaarde, Netherlands (above) has been designed to make crossing by cycle (and foot) simple and safe. The crossing point is set back on a decent width and rectangular island, crossing is in two parts and people only cross one traffic lane at a time. The roundabout is designed to promote low entry and exit speeds, so drivers have a bit more time to see people crossing. It's a safe design.


Let's compare it with this this roundabout on Buckden Road in Cambridgeshire. The crossing point is close to the roundabout. The crossing island is triangular and narrow at one end to help create a flare at the roundabout which promotes high entry and exit speeds. The crossing is in two parts, but it's over two lanes on the vehicle entry side and over a wide lane on the exit. This is an unsafe design; even if there are no collisions being recorded with people walking and cycling involved, it *feels* unsafe in use.

Comfort - the cycling infrastructure ensures that cyclists experience minimal nuisance.
Having to interact with motor traffic is a nuisance for people cycling. To be fair, the same could be said of people cycling from the perspective of someone driving. I don't mean that cyclists are a nuisance, it's just that in some situations, giving people their own clear space makes life far comfortable for everyone.


Gaasperpark, Amsterdam is the street which runs past Gaasperplas Station (above). It's somewhere which is away from traffic and where people walking and cycling have clear space. Out of shot, there is a drop off point, but there is no interaction. It's a comfortable place to walk and cycle with no traffic nuisance.


Having to mix with traffic is tiring. One has to be on constant alert and in many cases, this ends up having to try and think what a driver might be doing. This is not a comfortable experience and so minimising interactions with traffic either with cycle tracks or by building low traffic places is key. 

Exhibition Road in Kensington & Chelsea (above) comes from the opposite school of thought which essentially throws everyone together and expects the need to interact to be the controlling features. Unfortunately this is nonsense. Exhibition Road is one of London's "Quietway Links" (whatever that really means). In fact, in 2018, the street carried 8,757 vehicles per 12-hours (daytime) during the week and 7,316 at the weekend.

Despite the posted speed limit being 20mph, the 85th percentile speed in 2018 was 27mph. Looking at Figure 4.1 in LTN1/20, Exhibition Road is well into the area where some sort of protection for people cycling is required (or the traffic needs to be significantly reduced. The CROW manual in Table 5.3 is even more stringent - this street should have cycle tracks.

One useful snippet from the CROW Manual is that every stop someone cycling has to make means they need to use the effort equivalent to cycling between 75m and 100m to get going again. Go and count the average number times you have to stop on a shared path route with side streets and signals - that's your comfort being wiped out a stop at a time! You can also throw in minimising turns (on main cycle routes) because not only does that slow people down requiring energy to get going again, the chances of getting lost increase.


Storgatan, Malmö is within a central area of the city where motor traffic is either filtered out or heavily controlled. There are shops and other destinations that people cycling will want to visit and in doing so, a "cycling mind map" can be formed. Getting lost is uncomfortable and so good wayfinding is essential and this could be both using signs and streets which provide legible routes.

Smooth all-weather surfaces (which properly drain) enable everyone who wants to cycle to be able to do so all year round and they are therefore comfortable to use. Cobbles, unbound surfaces and hand-laid surfacing are not comfortable to ride over. 

The Five Principles – the balance
The quotation from the CROW manual at the start talked about the minimum requirements and these will be found in more detailed guidance. However, I think it's worth looking at the balance of the requirements in the round and it's worth acknowledging that some may be more important in some circumstances and compromises are not always a significant issues.


Gunnels Wood Road in Stevenage (above) is part of the towns famous and now rather worn separate network. It is objectively safe, although maybe subjectively unsafe at night. It is comfortable with smooth surfaces and gentle gradients. The problem is, though, that the network is not especially direct or coherent because apart from it taking ages to get anywhere (or at least it feels like that) and cycling is banned in the town centre. It's an attractive network to a certain extent, but it is so boring to cycle around.

Trying to deal with the balance or the compromise is the stock in trade for planners and engineers. This is pushed by space, time and very often politics. If we drop the bar for one or more of the five principles too much, we create gaps in the network, maybe not physically, but in how they feel in use.


A short section of reduced comfort and attractiveness might be acceptable if it remains safe, direct and coherent. The reduction in comfort might be a bit of a narrowing or even a section of shared path. However, constant compromise will start to become tiring and off-putting to use. If people can understand and see the end of the compromise, then it's going to be more acceptable. CS2 on Royal Mint Street (above) had building works over it for months, but the cycle track was kept open. It wasn't an attractive layout and the space was pinched a bit, but the extent of the compromise was both obvious in spatial terms and that people realised it was only for a finite length of time.

How above a layout which creates a slightly longer cycling route to avoid a large junction which reduces directness, but in being away from traffic and complication, the other principles are enhanced.


Sacrificing safety will discourage people. If we are dealing with a route then compromised safety will create a weak link with no work around (whether that's through design or a short term issues such as street works). People walking should not have to be drawn into compromises. If something has to give, it should be space for motors and then cycling space (subject to the other considerations). 

Bradford Street (above), had a pop-up protected cycle lane built last year as an emergency response to Covid where people leaving public transport needed alternatives. It's a pretty good scheme, but the bus stops are a compromise which impact on bus passengers. This is recognised by the City and it is hoped to be upgraded to a more permanent layout.

If there is something which doesn’t work at the local level, the solution is at the network level. In my talk, I mentioned some of the narrower streets radiating from the centre of Oxford. It may be that there are solutions where some roads are for general traffic and others are heavily filtered to prioritise cycling and bus access. Delivered alongside a network of Low Traffic Neighbourhoods, the City could help to do something about the 60% of trips which are driven into the City.

Conclusion - the acid test
In concluding my talk, I suggested five things which might be indicators that a cycle route is doing well and which are perhaps harder to capture than in numbers alone;
  • People of all ages cycling.
  • People using non-standard and adapted cycles.
  • People cycling side by side having a chat.
  • Mistakes by all road users are forgiven.
  • Children being children in perfect safety!
Looking at the photo of the kid cycling along the Embankment cycleway in Central London immediately tells you that the five principles have been well-considered. The route is coherent as it's obvious where it goes, the junctions are pretty good and it helps people get from A to B. This section is a direct line from the edge of the East End to the City and then Westminster.

The kid is objectively safe and he feels subjectively safe enough to be able to pop a wheelie. The surface is machine-laid, traffic is physically separated and the path is wide - it is comfortable. It's also an attractive route because there are famous sites to see including the popularly known "Big Ben" clock tower before the route swings to Parliament Square.