Voorrangsplein! Part 3

One of the things that constantly impresses me about Dutch highway engineering is that they are not afraid to experiment and improve.

I was lucky enough to visit the Netherlands again a few weeks ago and my nerdy highlight was a cycle infrastructure safari around Utrecht with Mark Wagenbuur of Bicycle Dutch blog fame and our ride took us through a type of junction which has been intriguing me for ages - the voorrangsplein or "priority square" junction.

This post is actually part three of a series in which I wrote about the junction form back in February and March of 2021 as we were still grappling with Covid and I was wondering when I might venture back across the North Sea. Fortunately I have been able to visit several times since and each trip gives me further insight into the kind thinking that we could easily import into the UK and that includes the voorrangsplein design.

My first two posts looked at the design from first the motor traffic point of view (because it is a motor traffic feature) and then how walking and cycling could be added. My trip to Utrecht allowed me to see a couple of examples in the flesh and Mark provided some additional local knowledge. 

The other little development is I put out a little slideshow of my latest trip which included one of the junctions and that prompted a discussion with a Dutch colleague who pointed me and another UK colleague at the general design guidance for the junction type as featured in the CROW ASVV Recommendations for Traffic Facilities Within Built-Up Areas 2021 which is a much larger piece of design guidance than the CROW Design Manual for Bicycle Traffic which many in the UK will have heard of. I have the 1998 English version, but the current one is only in Dutch and so I've had to do a bit of translating with Google!

I will add my usual health warning that Dutch guidance has no legal standing in the UK, although lots of it will be of interest to a UK audience and many practitioners use it for inspiration and ideas (myself included - more on law and guidance here). Some of the tools, techniques and layouts are not compatible with UK legislation, but in my view we could very easily import the voorrangsplein design.

As we found out in the second post of this series, the layout was first used in Hilversum in 2007 to replace a signalised junction. The design developed from the LARGAS idea - langzaam rijden gaat sneller or driving slowly goes faster.

Since 2007, the junction has become a feature of guidance and the design has popped up all over the Netherlands. In Utrecht, it has been used at a couple of junctions which are part of the Western City Boulevard project which is squeezing out some motor traffic capacity in favour of more space for people and green space on the city's ring road. I made a video of a section of the project from my recent visit in which you'll see a couple of voorrangsplein junctions.

The project still has retained a fair chunk of capacity at the larger junctions and given these are largely the flow constraining features, removing a lane in each direction between them isn't a huge problem from a capacity perspective. Before we take a closer look at one of the Utrecht examples, it's worth taking a slightly deeper dive into some of the features of the junction type. 

The guidance suggests that the design should be used at intersections of distributor roads with access roads, and that the main road can operate with a maximum of 25,000 vehicles a day. As you might recall from the previous posts, the junction is part of a single carriageway layout (locally dualled or with a very large traffic island on the approach) and so 25,000 vehicles a day is a very high flow indeed. 

When the main road is running clear, the guidance also suggests that the main road can feed up to 1,200 vehicles a day in each direction through the junction type (just under 10% of the daily flow). In some situations this might be seen as potential constraint because peak hour flow might be a touch higher, but as I have suggested, 25,000 vehicles is very high for a single carriageway road and we really need to be designing for traffic reduction in my view. 

The junction type is not for high speed roads and indeed, the guidance suggests that it is a useful "gateway" feature for stepping driver speed down. Because of the horizontal deflection it provides on the main road and for the side roads being mainly for access, it's a chance to reinforce a change of environment. Above is a simplified layout I have flipped for the UK and I've annotated some of the key features. The main thing to consider here is that it can be easily seen that drivers are able tackle the junction in stages, dealing with other traffic streams in bite sized chunks - it is an easy junction to drive through!

The lane widths are interesting. The guidance suggests they be in the range of 2.9m to 3.5m. The narrow lanes help keep driver speeds down, but there are options to add overrun areas to accommodate larger vehicles - rammelstrook or rumble strips. I can see some UK network managers shuddering at the narrow and locally dualled sections which might be a problem in the event of a breakdown, but we probably shouldn't design for what is a fairly irregular event.

The junction form is still space hungry, but compared with a signalised junction of a similar capacity, the layout tends to be elongated and provides space for landscaping where being used in retrofit. So, the Utrecht examples are interesting because the overall highway footprint remains, but the elongated nature of the junction and the general road diet means an awful lot more space is released for landscaping as well as walking and cycling space.

Let's take a look at one of the junctions - Marnixlaan with Royaards van Den Hamkade/ Van Egmondkade (above). In the photograph the main road (Marnixlaan) splits either side of the kidney shaped central island. Around this island you can just see a left turn lane and the black car to the left is entering the other left turn lane coming towards us. To the right there is a black car emerging from Royaards van Den Hamkade just out of shot that car has also cleared the cycle track to wait in a pocket before joining the main road.

Above is a photograph where I turned a little more to the right and the cycle track and footway can be clearly seen, both with priority over the main side road. The video below is a pan across the junction from its south east side and then a quick look at how the Royaards van Den Hamkade arm works. It's worth watching a couple of times to see how well things flow for all users.

Royaards van Den Hamkade is part of a route which connects to the city centre and so arguably it is more of a distributor road than an access road, although the route does tend to fizzle out as it meets the city's ring-canal. The Van Egmondkade arm is also more of a distributor road which continues as a route to meet the regional road network. 

The other thing to note is there are two way cycle tracks on both sides of Marnixlaan whereas the guidance shows (but doesn't require) with flow cycle tracks. Of course, walking and cycling is an additional to the basic motor traffic junction and locally, the two way tracks make sense at a network level. 

The photograph above is the the left of the first one which shows an uncontrolled crossing for walking and cycling of the main road which is in accordance with the guidance (but signalised crossings are used elsewhere) and you can just make out that the cycle track coming in from the left is one-way as is the crossing by virtue of the no entry signs. For cycling, this junction is the interface between one-way cycle tracks coming from the southwest and the two side roads and then becoming two-way on both sides of Marnixlaan off to the northeast so save having to cross the main road further on.

The final piece of interest here is the set of traffic signals on each approach to the junction on the main road. I have already said that the junction form is unsignalised, but in this case, the signals are used to hold traffic for a very short time if the junction has started to hit capacity which in theory could be from traffic on the side streets, turning right in the junction or perhaps lots of people cycling across. The photograph above shows the signals on the southwestern approach and you can note the one-way nature of the cycle track.

You can also see the signals here which are just red and green aspects when in use and some traffic loops for drivers and cyclists here. The traffic signals only switch on when needed and are set away from the junction so they don't create any confusion that they are part of the junction.

And there you have it. Hopefully this has helped get under the skin of the voorrangsplein to show lots of little things working together to create a really useful junction design.