Fabulous Fendon Road

You wait ages for a post about roundabouts and three come along at once. After looking at the proposals for North Tyneside and the continental roundabout in Islington in recent weeks, have I actually found a Dutch-style roundabout in the UK?

Well, the other week, I took my trusty folding bike to Cambridge to have a look at a scheme I had hoped to visit last year, but lockdown meant I couldn't travel more than locally. 

The scheme is the Fendon Road roundabout which was rebuilt as a UK equivalent of a type of Dutch urban roundabout where walking and cycling is prioritised over traffic. As a reminder, the Dutch guidance looks like this for this type of roundabout (with general and cycle traffic orbiting anti-clockwise);

This is the CROW Design Manual layout. There are quite a few dimensions to think about;

• R1 (radius to edge of circulatory area) = 12.5m to 20m
• R2 (radius to outside of central kerbed island) = 6.5m to 15m
• ra (entry radius) = 12m (with the central kerbed island)
• rb (exit radius) = 15m (with the central kerbed island)
• B (circulatory lane width) = 5m to 6m (depending on R1 and R2)
• b1 (overrun apron) = 1.5m (minimum of 1m)
• b2 (cycle track width) = 2m to 2.5m
• b3 (cycle cross approach) = as large as possible
• L (distance from edge of roundabout to cycle track crossing) = 5m

The various dimensions affecting the carriageway are designed to require the drivers of small to medium-sized motor vehicles to actually slow down and use their steering wheels which means that interactions with people walking and cycling across the arms and other drivers within the junction are controlled. 

If there is collision, then speeds are low and the risk of serious injury is reduced - sustainable safety in action (but it doesn't eliminate safety risks). The overrun apron gives the drivers of larger vehicles a little more space without making it easier for the drivers of smaller vehicles to speed. The absolute key to the design is having one traffic lane in and out on each arm.

The 5m set back of the cycle crossing means there is space for drivers to stop as they leave the roundabout and the crossing is in a location where driver speeds from both sides are low. The landing for the floating zebra crossing gives people walking some space to pause between crossing the cycle track and then the traffic lanes. 

Dimension b3 is worth pointing out because the larger this is, the more time people driving and cycling have to see each other people cyclists cross - it's gives a little more chance for people to react. My thanks to Calum for noticing a nuance which I had missed. Of course, this dimension also makes sure pedestrians get a decent bit of space between the cycle track and carriageway.

You'll notice there isn't a width of the refuges within the crossings specified because these are more about keeping drivers regimented than expecting people walking and cycling to wait - they are given priority after all; but the refuges are rectangular to force lower driver approach speeds. The usual UK approach is to have triangular refuges to make it easier to driver through at speed. It's worth noting that in the UK, that the addition of refuges to zebra and parallel zebra crossings means that they should be treated as two crossings by users.

I'm not going to go into each detail of the Fendon Road scheme, but on the whole, most of the key issues are dealt with in what is actually a pretty challenging site space wise.

The photograph above is the view into the roundabout from the western arm of Queen Edith's Way. On the approach, there is no cycling infrastructure on what is a pretty horrible road to cycle along. To join the layout, one merely moves to the left to join the cycle track. There are no dropped kerbs that would tip a trike user which is great. The four arms of the roundabout are not equally placed around a circle, the junction is skewed so pairs of arms have a small angle between them which makes it really hard to accommodate left turning vehicles.

The general arrangement of the roundabout has a low upstand kerb to the right (as you cycle orbitally clockwise) and a 45° splay kerb to the left (above). The mini-zebra crossings over the cycle track are on low humps with the levels such that there's a gentle slope across the crossing area from footway to carriageway. Some have suggested that drivers should also have to negotiate a humps which I have a little sympathy with, but the levels really work well and the roundabout geometry slows drivers anyway.

The designers have made the zebra crossings for pedestrians nice and wide which helps both with conspicuity and helps smooth the desire lines people take with different routes through the junction (above).

The vehicle entrance and exit points (the 'L' dimension) is 5 metres which meets the requirements for this type of roundabout and the orbital cycle track is properly circular and meets the carriageway nearly at 90°. This means that drivers wishing to turn left off the roundabout have a good view of cycle traffic and people cycling do not have to look behind them (but as a user, you do need to pay attention to what's happening). 

Because the cycle track is circular this does mean that the cycle crossings are not strictly parallel to the zebra crossings and so this doesn't comply with the daft rules on parallel zebra crossings which require a standard 400mm gap. I don't know if Cambridgeshire County Council is applying for a special authorisation for the layout from the Department for Transport (they should for completeness, and DfT should change this rule).

I've reproduced Figure 10.37 from LTN1/20 Cycle Infrastructure Design which does have "properly" parallel zebra crossings, but people just don't flow like that in a compact situation like this. I'd also point out that the figure's dimensions are lost because of the poor quality of the downloadable PDF.

One piece of detail I was a little concerned about was the choice of gully grating. On the one hand, the unit seeks to minimise intrusion into the cycle track and having part of it in the cycle track drains a bit better than an inlet unit which would be within the kerb. The issue is the longitudinal slots which are fairly short, but perhaps just long enough to catch a narrow or small wheel.

The circulatory area of the carriageway is compact to slow drivers down and features a kerbed apron with a stone sett infill. From a maintenance point of view, I do think that this will be a point of future failure because heavy vehicles and setts simply don't mix long term. I think I would have used imprinted asphalt in this situation as it could be formed to give a kerb-like edge and a textured surface to dissuade the drivers of small cars. 

The eastern arm of Queen Edith's Way is similarly poor for cycling beyond the roundabout, but again, there are decent transitions (above). One odd thing about this arm is that there isn't a parallel zebra crossing. There is an existing vehicle access to a house which means there is a cycle track that drivers give way to with a separate zebra crossing a little further out (below).

This is a perfectly legitimate layout, but it's not quite Dutch. But, it it's a practical solution to the problem and remains reasonably consistent with the design principles.

The junction has some really nice planting and as is the UK way, it has sprouted many Belisha beacons (featuring "halo" light up surrounds for maximum conspicuity - above).

The other little thing which made me smile were the bollards with little cycle and turn left traffic signs just to be sure, despite the layout being very legible and obvious to the user. 

The cycle tracks were perhaps a little tight in places, but they are machine-laid and red - something adopted all over Cambridge (and my favourite colour). If I were to be *really* picky, I would love to have seen the footways paved in light grey block paving to soften the the visuals of the scheme and to differentiate from the carriageway, but I can't have it all! 

Here's a short film of me cycling around the roundabout. What you don't see is me concentrating on what drivers are doing, but because the layout is so intuitive, I only need to worry about what's happening immediately near me. It's easy to see drivers leaving the roundabout as I approach the crossing and as I cross I can see what drivers to the left are doing, (reasonable) safe in the knowledge that the geometry is slowing drivers down - you can see the generally good driver behaviour in action and it all just flows.

The designers have worked incredibly hard to get this scheme squeezed in and working for all users - we often hear about "all users", but it's used correctly here. Before I sum up and offer some closing comments, it's worth having a look at this stunning video by Durman Stearn, one of the project's contractors.

You can really see the elegance of the project and how it all fits together from above.

So, is it Dutch? Pretty much and what is more, it shows that behavior can be changed through design. The UK is terrible at designing roundabouts, a subject I keep coming back to. We tend to design them for maximum traffic capacity whereas the Dutch tend to design them for safety and smooth traffic flow (maybe up to 25,000 vehicles a day for this type).

Slowing things down to speed up overall journeys is known across the North Sea as LARGAS which is an acronym (langzamer rijden gaat sneller) translating to mean "drive slower to go faster" (thanks for the translation, Mark Wagenbuur) or in other words, driving more slowly, but more smoothly means you get to your destination in a more reliable time. In the context of this roundabout it also means drivers can see people walking and cycling in good time and by easing off their speed a touch, they barely have to stop too. 

Here's another video from the excellent Ideas with Beers series which looks at the scheme and there's a talk about before this piece the off-street trials which took place in 2013 and which I experienced in October of that year (yes, it took that long between someone testing it and someone building it).

Would I build this type of roundabout in more places? That's a firm "depends". Cambridge was probably the right place for this scheme because of the fact that lots of people cycle in the city and people who drive there should expect people cycling, although the junction doesn't sit within a network of protected cycleways which is a significant disadvantage to a proper shakedown.

Care should always be taken when copying other countries' designs because the rules and design approaches have subtleties. On the one hand, the blogger David Hembrow suggests we should go for designs where cycle traffic gives way and his blog posts on the subject are vital reading for designers and campaigners alike because it is an approach we can easily copy in the UK. On the other hand, many parts of the Netherlands have decided to push on with the version giving cycle traffic priority in all urban situations and the blogger Mark Wagenbuur explores that in his blog post.

Where the cycle priority design has been chosen, this has been because a municipality have designed to give more cycle priority everywhere and to that extent, priority at roundabouts is consistent and something drivers should be able to anticipate. In the UK, we will have to pick the right locations and unless the geometry is controlled as well as the Cambridge example, we will build risky layouts that lull people cycling into a false sense of security.

There is only one team in the UK which has built a Dutch style roundabout and that's the Cambridgeshire team. I hope that in due course we'll get some longer term learning and study information from the scheme and I'd love to be involved in the design of one myself, so long as it is in the right location. I also think we need to build some of the other type because these can be safely rolled out in far more suburban and rural situations. 

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!

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.

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.