Saturday, 22 February 2020

Chislehurst Crossing Challenge

The Chislehurst War Memorial junction in Bromley, Southeast London is a good example of a layout where traffic control design has just evolved over the years and people on foot have simply been ignored.

Local campaign group, the Ashfield Lane Road Safety Group, has been pushing to have pedestrian signals added to the junction, especially as it's a location crossed by local school children.

The junction is formed by the A222 Bromley Road/ Bromley Lane and the A208 Centre Common Road/ Royal Parade. Despite being A-roads, 3 of the arms are single traffic lane approaches with Bromley Lane being a two-lane approach;

The junction is skew - that is, the arms are not at 90° to each other, they form a shape like the flag of St. Andrew;

You might just notice the red lines on the aerial view above; that's me highlighting the position of the stop lines for traffic on the approaches to the junction. The narrow traffic lanes and fairly tight corners means that when large vehicles are turning, waiting drivers need to be set right back as the drivers of large vehicles need the full width of the road to turn and over quite a distance.

As the network, there's other, smaller roads further away from the junction which look to me that they will have a rat-running problem with some people driving to avoid the junction. The junction itself sits within the north of the pair of Chislehurst Commons which may well explain which the junction has never been enlarged - there's a local act of Parliament giving local management powers to a board of trustees.

Anyway, back to the junction. The method of control is quite simple with two traffic stages running with east-west traffic together and north-south traffic running together. At the end of each stage there will be an all red period to allow right turners to clear the junction before the next one comes in. For people wanting to cross the road, they either have to fine a gap in flowing traffic or to try and cross in the all red period.

So what is the solution for foot traffic? The narrow roads, limited space and the fact the junction is in the common means that it won't be widened and so the solution is to add a third traffic stage which would run an all-round green man.

The image above shows roughly where I'd look to place the pedestrian crossings (red) to keep them on the desire line as far as possible, but away from the corners and turning traffic as well as where tactile paving would be a pain to detail. The blue crossing is an optional diagonal crossing on the shortest diagonal. The staging diagram would be as follows;

The diagonal arm has a 12m crossing distance and the longest side road crossing is Bromley Lane at 9 metres (the eastern arm of the junction in the image above). Crossing distance is important as it informs the time people have to cross and from a traffic signals design point of view there will be pressure to keep delay to motor traffic to a minimum, not only because the politics of all of this stuff, but also because delayed drivers will rat-run more.

There is a compelling argument to look at these issues in an holistic way at the network level (into which we bring cycling for transport), but in the short term, it would be relatively straight-forward to add a pedestrian stage, even if the diagonal were omitted, because it should be a basic level of human decency to provide crossings at signalised junctions.

I hope the local road safety group can push the council to work with Transport for London (the signals authority) to get green men added to this junction and hopefully this post will help explain what needs to happen.

Saturday, 15 February 2020

Parking - Perpendicular, Parallel or Pitched*

Prompted by a tweet by Mike the Navigator, I thought I would muse about the way we design on-street parking.

I guess it's a fairly mundane subject and you'll be pleased to learn that I'm not going to go into the legal process, but suffice to say, this week I'm interested in the design of parking where we mark out bays in the road.

There are three main ways to mark out parking bays (in relation to the kerb);




The choice of layout for the street will often be governed by its width because clearly, perpendicular and echelon take up more of it. 

You will have seen parallel everywhere and as a rule of thumb, 6m long bays will be sufficient for most people to reverse into to park - some people struggle to parallel park of course and so you see them pulling in and then trying to jiggle the car back and forth to hug the kerb! 

Perpendicular parking will certainly be familiar in car parks and for many people, they'll be easier to drive into than a parallel bay, although many will park "nose in" and then reverse back into traffic from a position of very poor visibility such as this example from Bristol. Pulling out from a perpendicular bay requires the driver to look at traffic coming from behind and with vehicle blind spots, vehicles parked behind and in some cases people having limited movement, it can increase risk as people who cycle will attest to.

If one reverses into the space, then leaving it will be from a better position of visibility. Perpendicular parking also means that nobody needs to exit the vehicle into live traffic and if people reverse in, they can load the rear of the vehicle from the footway. In a street context however, there's always the issue of drivers parking with the vehicle overhanging the footway and reversing in does turn exhausts towards people. 

Echelon parking is perhaps even more unusual to see anywhere, but if it is done correctly, it too can offer a safety benefit. The key to a properly designed echelon parking bay is its orientation. With my sketch above, drivers on the side of the street with the bays are forced to drive past the bay they have selected and reverse in. Leaving doesn't quite have as much visibility for the driver as a perpendicular bay, but they will soon get a full view as they emerge which is far better than reversing out.

The problem is of course that on a two-way street, people driving on the other side of the road can easily swing across the road and park nose in. Despite being quite unusual, examples we can find are often the wrong way round such as here in Southend-on-Sea where a huge area given over to echelon parking;

I've done a big of digging around and it's hard to find a UK example of where it's been done properly - there was an example in Islington, London, but looking at Streetview, the layout today has been changed to parallel parking.

As you can see from the old Islington layout above, the layout is being used properly because the angle makes it obvious that one reverses in. I think that the arrangement works best on one-way streets (for general traffic) because drivers have no choice but to reverse into the bays.

There is local guidance in the UK. Manual for Streets has a guide to parking bay layout on Page 111 and designers are encouraged to arrange bays so they are reversed into. So there you have it, we usually see parallel parking on our streets, but in the right context, it's not the only option. 

*OK, I mean echelon

Sunday, 9 February 2020

Who Is Liable

I wrote about risk and liability from the designer's point of view back in 2013, but this week I thought it would be worth revisiting the subject. 

The reason for revisiting is because there are designers out there worrying about using continuous footways and cycle tracks over side streets in case they are sued. The fear comes from a concern that should there be a collision after doing something seen as innovative or unusual, then they are in the firing line.

I do understand their concern because let's be honest, people like to operate in their comfort zones and for a highway engineer, carrying on with a design approach which has decades of use behind it is very comforting. Let's look at four junction layouts (some of you will recognise this graphic);

The two on the left are really familiar and from a driver's point of view, one is invited to assume priority over anyone crossing the side street, despite what the Highway Code recommends that they only ever read when learning to drive. This layout being UK custom and practice means that people walking are told to be subservient through the design.

This approach was never critically reviewed before it was rolled out, it has its roots in history where at some point (which varied across the world), we started building footways (sidewalks) to keep foot traffic up out of the mess and filth of the street or to offer a little protection from carts. Over time, footways became commonplace, but in modern times they have evolved to be the bit that people stick to while walking leaving the relative high power of the motor vehicle to claim the space.

The top right image is also familiar and part of a generally modern idea of trying to give some priority back to walking. The layout may suggest that both people walking and driving could take priority, although it would very much depend on the person and the location. From that point of view, a potentially ambiguous layout and one where where someone making an incorrect assumption means the most vulnerable party in a collision comes off worse.

The bottom right is of a continuous affair which suggests that drivers may be guests, although we'd probably look to provide some tactile paving to assist visually impaired people who require assistance.

Across the North Sea, the layout is old hat and when correctly applied one can stand at a junction like the one above (Amsterdam) and see it work without any significant issues. It's a design that you do find in the UK, sometimes very old layouts, but it's never really taken off as an approach. There are some contemporary examples such as Walton-on-the-Naze (below) which was built before we started talking about continuous treatments as a "thing".

So, if we were nervous about doing something new, does this nervousness come from ourselves not having tried it or because nobody else has ever tried it? Clearly with lots of examples in the UK and elsewhere, being nervous has to be an issue for the individual. What's the way forward then?

At the heart of all of this, I don't actually think this is a radical design approach because if you think about the number of driveways we have in the UK which still look like the footway, then there must be millions of crossings of the footway every day with very little risk. The "new" risks will be applying a fairly unusual design to side streets and in the case of continuous cycle tracks, adding cycle traffic to a conflict point.

The key is to be clear in setting objectives, how we use evidence and how we record our decisions. The next part of this post will be to set out a methodology for developing a design for the unfamiliar using continuous treatments as an example. There are of course other ways to do it and you may pick a different order or other stages.

This is key. As a designer, how confident are you that you have enough knowledge of design, legislation and road safety to be able to adapt your to a new situation? What training and experience do you need to design this "thing" you are interested in?

It is a bit chicken and egg I know, but if you're design response is to revert back to bellmouth junction design then I wonder if you are competent to design that given how things are changing. Be honest with yourself and others. Get some help in and learn from that help. Being involved means that you'll gain experience and understanding.

Setting objectives - What are we trying to achieve? 
Pretty simple really, I think we're trying to provide side road treatments that assist people walking and cycling to continue to move smoothly with interactions with motor vehicles taking place in a managed way.

We are not providing absolute priority because that is only possible with traffic signals and zebra crossings, but we are providing implied priority which should be understood by all users.

Literature and policy review
Are there any studies into the thing you are trying to design? What were the conclusions? How old was the study? For continuous treatments, I found this study commissioned by TfL after a minute of Googling. There's some interesting discussion based on different design layouts. There is more out there if you look a bit harder. Unfortunately we have yet to have any UK guidance

Is there legislation covering the use of continuous treatments? Not specifically because they are not a "thing" defined in law as a zebra crossing is. Well I wrote about my view on the law and continuous treatments here - I am not suggesting citing anything I have written as policy or legislation, but there is a thought process to go through and you need that knowledge of design, legislation and road safety.

Robert Weetman goes into a lot of detail on what we should be looking to achieve in this blog post. Robert, like me, is at pains to point out that it is essentially for the designer to understand the risk, but there is nothing stopping us from reading articles and forming considered opinions.

Who else has done the thing you want to do? What worked and didn't work? Is there data available? If it is an idea from another country, how does the legal system translate to the UK? Does the design rely on administrative rules or does the design explain how to navigate?

For continuous treatments we have lots of UK examples now and in fact, I don't think we even need to look to any other countries. They are established and understandable treatments and you can easily visit them and see how they work. Ask the people who designed them about their experiences too.

What does the data say? Look at casualty data for the existing site and look at the traffic flows (people walking and cycling included). Does motor traffic dominate the junction? Will motor traffic flow need to be reduced? What are your expected walking/ cycling flows and will they outnumber motor traffic flows?

In some ways, not having formal guidance might push us to be more critical of our approach. If there was a table that said with X vehicles and Y pedestrians the approach is safe, then we risk people simply ticking boxes.

Data also extends to using video surveys, site interviews and repeating data gathering for the layout after it's built.

I don't mean chuck out a letter to the neighbours and see if they object. Discuss the proposals with people who might be most affected such as visually impaired people, wheelchair users, local schools and so on. Be prepared to adjust and refine your approach.

I was of the view that we can just push on with a footway across a side street until I was told that some visually impaired people want to know that they are in a location which would have a higher likelihood of encountering a motor vehicle and counting side streets help with navigation.

The solution is blister tactile paving and in fact, not having a radius kerb to cut paving into (because of the continuous design) means a tider job with the tactiles (no little pieces) which means a lower risk of them failing (look above at the example from Walton-on-the-Naze to see what I mean).

Risk assessment
I've also covered risk assessment previously, but it's a useful design tool. The aim of a continuous treatment is to give people walking and cycling a smooth experience across a side street and that is influenced by how each user interprets what they encounter.

For example, running a cycle track across the side street will invite a person cycling to continue because it looks like their space;

The photograph above (Blackfriars Road, London) shows a carriageway level cycle track which invites one to keep cycling through the design, but perhaps it's not as good as my earlier Dutch example.

The principal risk is a person cycling being hit by a driver turning out of the side street and so using a matrix I've talked about before, here is a quick assessment (just for illustration, I have no background data to rely on);

The likelihood is linked to the number of drivers emerging and cycle traffic flows. The consequence is injury, but drivers will be emerging slowly, so an injury is probably in the "medium" area.

So I reckon a medium risk of someone being hit. I've given this assessment because perhaps the side street is quite busy and for a 2-way cycle track, drivers don't always look both ways.

A way to reduce the risk is to reduce the conflict and so we could make the cycle track one-way to remove the problem of drivers not looking in the "unfamiliar" direction. Let's reassess the risk;

The consequence of someone being hit is the same, but getting rid of the unfamiliar direction reduces the likelihood and so using the simple red/ green/ amber approach we are in the green and so we can be reasonably happy.

But wait, we can't make the cycle track one-way, so do we go with design? There is no reason why we cannot because we are judging all sorts of things, but we might decide to adjust the layout of the side road to slow drivers down even more - we could put up a sign explaining a two-way cycle track, but a sign is essentially an administrative control which does help us in the long term.

Along a whole scheme, we might have fewer problem locations and so in the larger scheme of things where we are trying to transform an area we might note the risk, but judge it to be acceptable because because we don't consider the outcome of a collision as one which would result in a serious injury.

Road Safety Audit
Get an independent safety review undertaken, but it needs to be with people who understand the objectives and are competent in that type of design. Having people who do nothing but audit motorway layouts look at this type of layout probably isn't going to help.

The worry at the back of the designer's mind is being sued. You either work for a local authority or a consultant working for a local authority. You will never be working with total authority or autonomy because building stuff on the street has to go through some sort of process and at some point there is an agreement to proceed. In other words, it will never be 100% down to you.

But let's imagine the worst (and this is pretty hypothetical). A person cycling is hit by an emerging driver and hurt. The cyclist takes out a civil claim against you personally. Your defence will be that you are competent in what you are doing and that you've followed a structured design process which has taken into account the things I written about (and probably a great deal more).

It's a good idea to keep records of what you've done, but even if you haven't you will be able to explain the process logically (although writing stuff down is a good idea). You will be able to show how you have mitigated the risks through good design and understanding how your design works.

I really don't think that continuous treatments are innovative, but their design does change how risks might be viewed because they are not custom and practice. The good news is that the more of them that we build, the more that the people using them will become familiar with them. The tiny risk of being sued will be even smaller.

Saturday, 1 February 2020

Vision Zero - A Swedish Introduction

I'm looking across at the mainland again this week towards Sweden and the country's Vision Zero programme.

Sweden is held up as a progressive nation when it comes to dealing with road death, but it wasn't always the case with road death being treated as an everyday occurrence. The change in approach came in 1995 when five young people were killed in a crash on the E4 motorway in Stockholm. The driver of the car they were travelling in ended up crashing it into a lighting column foundation and it was this event which started the country on the road to Vision Zero.

The incident caused Claes Tingvall, the traffic safety director at the Swedish Road Administration, to start thinking about the country's approach to road safety which placed the blame for crashes with victims. Tingvall begun to think about the issue after he was told that the foundation was simply going to be replaced without any thought about preventing a future occurrence.

Tingvall and his team wondered why it was only the road system where victims of crashes were blamed rather than the system as was the case with aviation where risks are systematically designed out. His team proposed designing out what is dangerous. 

He considered three basic points which are the basis of Vision Zero;
  • Life is more important than anything else,
  • We [professionals] are responsible for safety,
  • We [professionals] know what to do.

By 1997, the Swedish Parliament adopted Vision Zero (despite some being against it) as policy. The simple position was that nobody should be killed or seriously injured on the road network and that it was the job of professionals to design safe systems - both vehicles and roads.

Tingvall and his team started to systematically look at what was killing people on Swedish roads and it turned out to be head-on collisions on high-speed single carriageway roads. The traditional solution was to dual the roads and build central reservation barriers, but clearly this is a very expensive undertaking in terms of land and construction, as well as not being needed in many cases from a capacity point of view. Tingvall proposed converting the roads to 2+1 operation.

The 2+1 layout essentially divided the existing roads into three traffic lanes (the high speed roads were already wide). Two lanes would run in one direction with one in the other and the directions would separated by a flexible safety barrier which could absorb energy in the event of a collision.

Every so often, the arrangement would swap to give drivers a chance to overtake slower vehicles. Where left turns (UK right) were needed, then protected turn lanes would be provided within the same alignment, but generally not within the two lane direction (so people didn't have to turn left from a "faster" lane - grade separation is the solution for multi-lane layouts). Here is Tingvall's original 1995 sketch;

Looking back at the idea, it seems to ridiculously simple and a space-efficient solution. Sweden doesn't have a dense motorway network and so many of the roads we're talking about are part of the national road system. They are important for long distance traffic, but where there isn't the need for high capacity. There are some dualled Swedish motorways as well as some operating with the 2+1 layout.

Of course, the 2+1 approach allows regular overtaking of lorries, so there is some capacity gain over a conventional layout where risky overtaking takes place.

There was significant public resistance to a plan to trial a 2+1 system, but against the backdrop of having his job and reputation on the line, Tingvall was allowed to proceed. The trial was taken forward on the E4 north of Gävle which had a high level of fatalities and it was a huge success. The system has now been rolled out all over Sweden with high levels of public support and as driver, it is a safe and easy layout to cope with.

The photograph above is the E65 Malmövägen, near Ystad. There's one lane in each direction at this location, but you can see the barrier and there's a separate right left lane ahead. The central barrier is pretty much always wire rope which has some serious stopping power;

There is controversy with wire rope barrier in that it can kill motorcyclists who come off their bike (and slide along the road surface) and either hit the supporting posts or slide under and into oncoming traffic. Motorcycle groups and safety professionals are somewhat at loggerheads over the issue, but that's a whole discussion in its own right.

In parallel to developments in road design, the Swedish also started to look at vehicles. For many years, vehicle design was being looked at by European governments and in 1996 the Swedish National Road Administration (SNRA), the Federation Internationale de l’Automobile (FIA) and International Testing joined a programme which is famously known as Euro NCAP.

One criticism of the modern Vision Zero approach is that does in some cases rely on road users following the rules which can be challenging where people are determined to break them. The concept has also been criticised for being too focused on protecting drivers from each other and themselves at the expense of people walking and cycling, although to some extent this is possibly because initial work was dealing with head-on collisions.

The other issue is that concentrating on pure numbers of deaths and injuries is that it doesn't necessarily look at risk exposure, especially for those outside of motor vehicles. If you've scared or taken people off the streets, then they aren't going to show up in the data. Risk exposure looks at the likelihood of collisions based on distance or time travelled.

However, modern Vision Zero has evolved in Sweden it is now summarised as follows;

  • Ethics – people should not have to die in traffic; this is the fundamental part of the approach,
  • Responsibility – system designers must realise that people make mistakes,
  • Solutions – finding combinations that work; combinations work better than single solutions.

Some of the typical engineering measures which have developed from Vision Zero in Sweden include;

  • Median barriers to remove head-on collisions,
  • A move to roundabout intersections,
  • Speed limits based on what the human body can withstand in a collision,
  • Traffic calming – crossings, humps, road narrowings, chicanes etc,
  • Speed cameras.

The photograph above is of Strandgatan, Malmö. A local distributor road with a 50km/h (30mph) speed limit. A crossing point for walking and cycling on a wide refuge within a chicane to slow drivers.

Of course, this is not the end of the story. One of the collision factors the Swedes are going after is drink driving. It's a stated ambition that the country wants to introduce alcohol interlocks to stop people being able to drive over the limit. They're not there yet, but a scheme to stop drink driving has been rolled out at the port of Gothenburg.

Sunday, 26 January 2020

A Matter of Priorities

An interesting little quirk of UK cycle track design popped up this week and I thought it might be interesting to look a bit closer.

The subject is shared-use paths being given priority over motor traffic which was being discussed on Twitter earlier in the week in terms of making them as good as possible against the backdrop of a local authority refusing to look at separate walking and cycling space. Thanks to @24bitwarrior for the question and to @walking_boston for the link to an older piece of guidance from Sustrans.

Coincidentally, Adam Tranter tweeted a photo of exactly the thing we were talking about later in the week;

The location is here and if you have a look around the area, the treatment is unique, although it's at one end of a network of shared paths. It reminded me of a similar layout in Crowthorne which you can see here - there are others in the UK and it would be quite nice to compile a list, so feel free to tweet me locations.

The locations take a similar approach where you might have the shared-path (which strictly legally speaking is a cycle track which is shared with people walking) running next to or set back a bit from the carriageway and where it meets a side road, it is "bent out" from the main road as it crosses the side road. Bending out means that drivers can get off the main road before having to stop for cycle traffic.

As you can see from the diagram above, drivers would turn off the main road into an area at least 5 metres deep to give way a second time to cycle traffic. Apart from the design being used in New Town style estates, we know these are historic because the crossing is on a hump commensurate with the regulations at the time. Current regulations don't require a hump, but in the context we're talking about, I think humps remain useful to reinforce priority to cycle traffic and provide a level surface. We also often see red asphalt which lost favour in the UK (so did building cycle tracks of course).

Here's another clue. The photograph above is from "Cycle Friendly Infrastructure", a design guide from CIHT dating back to 1996. This actually has a separate footway, but the concept has been around for years and a study was undertaken by TRL in 2000 looking at this type of layout (with various configurations).

The TRL conclusions essentially fell back on the government's hierarchy of provision which is to make conditions suitable for cycling. 20 years on we know this doesn't work and if you need a cycle track, then surely the carriageway isn't suitable for cycling - this design has been used on distributor type roads which are awful for cycling. 

TRL more sensibly concluded that the traffic volumes in the side road should be low, perhaps under 100 vehicles per hour (which I am assuming is the two-way flow as it isn't clear). They also suggest that good visibility is required for people cycling to see and be seen (with commentary on main road flows) and that space is needed for the bend out layout.

The other issue is the layout of the junction looks like a traditional driver-oriented layout which invites motor traffic priority - the give way markings used in this way are going to be unfamiliar to many drivers.

I would also comment that the main road layout and volume will be an issue. A right turn pocket should be provided so that a right turning driver can pause before making the turn. This means they can see the side road layout and the need to give way to cycle traffic. Without a right turn pocket, people will have to find a gap in oncoming traffic and see the side road layout in one go.

A better approach altogether would be to have the side road as one-way out onto the main road which removes some of the conflict. With an estate, traffic signals can be used to manage conflict where 2-way traffic is required. The layout doesn't really seem to have considered people walking. We should be providing tactile paving which means on a shared-use path, people have to cycle over them which can be uncomfortable and slippery. 

I'm not entirely sure about the priority issue in terms of pedestrians either because strictly speaking, the give way road markings are about vehicle operators giving way to other vehicle operators, so people on foot might be in a grey area. We could in theory make the side road crossing a zebra, but for cycle traffic, we'd need to fudge in a parallel crossing.

Going back to the original question. I think it is going to be difficult to build shared-use paths with decent priority that people cycling can be confident with in terms of drivers giving way with these older layouts. I have less of an issue with shared-use paths in rural places where people walking are going to be a rarity, but in urban areas, they are poor for walking and cycling.

My thinking is we need to make the side road look like a side street, so we'll use our new entrance blocks at either end of the junction approach for a change in level with the carriageway width taken down to 4.8 metres to keep things nice and slow. The shared-use path should be a contrasting colour to the road (I like red) and perhaps flank it with some cobbles or setts to help with visual priority.

The area either side of the cycle track will be a contrasting material to the carriageway and shared-use path - perhaps grey block paviours would work. We can also introduce tactile paving, 800mm deep either side of the area which drivers traverse because visually impaired people need help - set them back a bit from the area being over-run by drivers to keep it looking less like a road.

The image above puts these items together, but clearly, a council which wants to put in shared paths won't want to spend money on junctions. They'll leave it like a traditional junction and people cycling will have to give way.