Saturday, 4 December 2021

Permission To Cross

Prompted by a question from Leo Murray, I have somewhat fallen down a little bit of a rabbit hole on the relationship between people asking for help to cross the street and how local authorities ration access to crossings.

Leo's (excellent) question was;

"How many pedestrians need to be crossing a main road at a location before a crossing is advised? I’ve been reading the Local Transport Note on pedestrian crossings but it does not give a number."

The question in itself suggests a run-in with a local authority policy which is so old, anyone working there probably doesn't know its origin and thus it has reached groupthink. It is so old, that it has never been recommended as a method throughout my entire postgraduate career (1995 onwards) and I had to go back to relearn it because I was so rusty!

The question alludes to a long defunct way of assessing whether a pedestrian crossing is warranted (bear with me), based on the relationship between traffic flow and pedestrian flow. This is known as the PV² rule and it was developed as a measure of the degree of conflict between people walking and driving to aid decisions on whether controlled crossings should be provided.

The technique requires continuous surveys to be undertaken with pedestrian and traffic flows. Pedestrian crossing flows are taken within 50 metres of either side of the proposed crossing site (which should try and pick an "average" crossing position if it is not clear) and both traffic and pedestrian flows in both directions added. The counts of pedestrians within 50 metres assumes that a crossing will see people within 50 metres migrating to it. 

Taking the pedestrian flow, P and multiplying it by the square of the vehicle flow, V, gives PV², which will be a large number and is expressed as 10(dividing the PV² value by 100,000,000 - 8 zeroes).


The PV² thresholds shown graphically

Where PV² is less that 1x108, then a crossing isn't warranted, where PV² is between 1x108 and 2x108, then a controlled crossing should be considered. Where PV² is more than 2x108, then we're looking at split controlled crossings. If we are considering a dual carriageway, then we would have to look at each carriageway separately, although that's going to make things even more complicated. 

The graph I have reproduced above comes from "Re-Examination of PV² Criteria for Developing Pedestrian Crossing Warrants", by Jain and Rastogi, 2016. It shows the type of crossings to be considered with the two thresholds, but with some nuances to pinpoint where zebra crossings might be appropriate which is essentially high levels of pedestrians and medium volumes of vehicles.

Interestingly, this graph is referenced in a few documents (mainly local authorities and reviews being done for them), giving a 1987 reference which I believe to be TA52/87 "Design Considerations for Pelican and Zebra Crossings". However, the graph actually combines two graphs in an older document, TA10/80, also titled "Design Considerations for Pelican and Zebra Crossings", below (apologies for the quality).


It's a bit tricky to understand all of this, so let's have some worked examples.


In the table above, I have shows hourly traffic and pedestrian flows for a 12-hour period. I have then found the four highest PV² values and taken their average in the penultimate line at the bottom of the table. Just below that, I have divided by 1x108, (100,000,000) to give the assessment score. In this example, we have 0.05x108 which means the site doesn't qualify for a crossing. You'll have to trust me, but the traffic flows (based on an urban area) are fairly modest and the pedestrian flows quite low. Let's run another example.


I have done the same again with different flows and this gives an assessment score of 1.41x108 which means we should be considering a controlled crossing as we are between the two thresholds and from the graph, probably a pelican (pedex now). In this example, we've a busier road with distinct peaks which could be a fairly busy distributor road and maybe even an urban A-road. We've also quite a lot more people crossing. Let's look at another.


This time, we have an assessment score of over score of 2x108 which means we should be looking at a split crossing, probably a pelican (pedex now). This is definitely an urban A-road, but it's far busier for more of the day than the previous example and we've more people crossing. One issue with the graph is that notwithstanding the score, you need at least 50 to 60 people crossing to hit the lines.

I want to show you two more tables. In the table below, I have taken the lowest traffic flows of the the three examples above and the highest pedestrian flow. The assessment score suggests no crossing is needed on the basis there is little crossing conflict with traffic.


The final table below does the opposite. Here we have the busiest road and lowest number of people crossing. Again, the assessment score suggests that no crossing is needed.


I wonder if you have worked out the pattern here yet? Let's work backwards. Given that very roughly speaking 2,000 vehicles per hour at peak is the upper threshold of an urban A-road (maybe a touch higher or lower, depending on the site), then we can reverse the PV² calculation to see how many pedestrians we need crossing to hit that 1x108 lower threshold. So, 100,000,000 divided by 2,000, divided by 2,000 again gives us 25 pedestrians crossing to hit the threshold, although 25 pedestrians doesn't really hit the curve on the graph either.


People crossing a dual carriageway on the desire line.
The lower PV² threshold won't be reached here.

If we are surveying a site with very high traffic flows, but few people crossing, does this take into account that the very reason so few people are crossing is because there is so much traffic? It has taken me a while to work through to this point, but this is one of the fundamental flaws with PV² because it immediately ignores suppressed demand and it requires a sweet spot of traffic flow and pedestrians. 

If you go back to the tables, lower flows of pedestrians or traffic skew the result. In other words, a quieter road means people don't need help crossing or a busy road can mean stopping drivers to let a few people an hour cross isn't warranted. It's a system of rationing the opportunity to cross based on current conditions and the numbers of people currently willing to cross. TA10/80 suggests that PV² is fine for most situations, but sometimes there are special cases;
  • Where a road divides a substantial community.
  • Adjacent to community centres and homes for the elderly, infirm or blind [this is the language as used in the document].
  • Adjacent to hospitals or clinics.
  • Busy shopping areas.
  • Outside school entrances.
  • Where the number of heavy vehicles exceeds 300 per hour during the 4 busy hours.
TA52/97 also adds bus lanes, intermittent pedestrian flows (e.g. railway stations) and "other local considerations".

Let's go back to the history lesson. At the start, I mentioned 1995. As well as it being the year I graduated, it was the year that two Local Transport Notes were published - LTN1/95 The Assessment of Pedestrian Crossings and LTN2/95 The Design of Pedestrian Crossings. The former superseded TA52/87 and the whole concept of PV² was withdrawn from official advice. LTN1/95 uses a much more detailed framework approach based on the local conditions (the special cases in the earlier documents) and the users who are crossing and who might wish to cross and so is therefore a subjective, but structured approach. Plus of course, traffic volumes (and driver speed) and pedestrian flows are useful pieces of data which can help inform a design strategy.

LTN1/95 continued to be the official guidance until 2019 when it was incorporated (along with LTN 2/95) into Chapter 6 of the Traffic Signs Manual. LTN 1/95 and 2/95 were then withdrawn. Unfortunately, Chapter 6 doesn't include the full detail of LTN1/95, including a proposed crossing assessment record sheet, although nothing stops practitioners using it or something similar.

So, since at least 1980 we have moved from a pseudoscientific method of assessment through to a structured assessment process to a perhaps simplified assessment process. Why does PV² matter then? Well, go and search the term "PV2 crossing" with your favourite search engine and wonder at just how many local authorities are still using it to assess requests for new crossings - it's startling.

Some local authorities use a modified version where they might add a weighting because of local conditions or lower the threshold. In many cases, the local authority talk about LTN1/95 (even in very recent policy documents) and then continue to use PV² as if a couple of decades of it being withdrawn don't matter. Some won't look at anything unless it meets the PV² criteria, despite the early guidance actually setting out special cases.

PV² isn't just old fashioned, it is discriminatory. If the site being assessed doesn't have dropped kerbs, then it's going to be hard to count people using mobility scooters or wheelchairs who cannot cross there now. It ignores older people who need more time to cross and who cannot judge vehicle speed very well, it also ignores visually-impaired people who tend to prefer controlled crossings, people travelling with children who will move more slowly, older children (who still cannot judge vehicle speed) and all those who aren't crossing because it's intimidating. Like much in traffic engineering, we end up counting those who turn up and they are either the fit and the brave or those who really don't have much of a choice and brave it anyway.

Using PV² in today is very much a system of rationing and even where used with weighting and structured assessments, it is a way for local authority staff to weed out requests and indeed to put people off from requesting crossings in the first place. I am not really blaming the staff because resources are tight and things have to be prioritised. Of course, there might be an officer who doesn't want to hold up drivers for which PV² is a handy tool and there are still dinosaurs out there. In the main it's a system of triage designed to protect councillors who make resource decisions, rather than actually admitting that people need help to cross the road at a particular site.

Pushchair crossing a dropped kerb with tactile paving.

If you help one group to cross the road, you
make it easier for everyone to cross.

One thing we should also consider. Pedestrian crossings are (like many features of the street) driver infrastructure and so if we remove (or significantly reduce) the source of danger for people on foot (i.e. traffic), then we don't need formal crossings and limited resources can be targeted at main roads where people very much do need help crossing. This is another piece of traffic engineering lore which has its roots in the 1980s and yet persists into the 2020s.

One thing I haven't found yet and that is where PV² actually came from in the first place. Jain and Rastogi's paper suggest the thresholds "were formulated using empirical data based on peak flows of 1980s", but that assertion is not referenced and in any case, neither TA10/80 or TA52/87 give any hints. TA10/80 replaces in part Departmental Circular Roads 19/74 which might have shed some light (but I have not tracked this down as yet), although it does pop up in Hansard.

My bet would be that this goes back to a time where UK traffic engineering started to import ideas from the USA. In the web based Manual on Uniform Traffic Control Devices (MUTCD), the "pedestrian four-hour volume" is used to justify a signalised crossing. Here, less than 107 pedestrians per hour doesn't warrant a crossing. It's not PV² of course, but it does rather seem to ignore the fact that people might not be willing or able to cross now.

This post has been fascinating to to research, although in truth, I may have been able to dig deeper if I had time to do more than internet research (but hey, I have a day job). If you think I have got something wrong (yes, maybe my maths) or if you have any other insight, I'd love to hear from you. I should thank Simon Hartshorne of National Highways for providing me with copies of TA10/10, TA52/87 and some other background documents which have helped me piece together 40 years of history.

Saturday, 27 November 2021

Rediscovering Sketching

As an engineer, I need to be able to communicate ideas and concepts to other people and one of the most powerful tools I have at my disposal is drawing.

There are obviously many mediums through which we can draw, but I tend to use CAD (computer aided design) or hand drawn sketches. For this blog, Microsoft Paint was originally my go to package for quick little diagrams, but once you had committed yourself, editing became tricky. I use the industry-standard AutoCAD for work, but it is incredibly expensive and certainly out of reach for the enthusiast and indeed small business. Luckily, I found NanoCAD a few years back which has a free version that I tend to use for most of my drawings for this blog as well as it being my tool of choice for freelance work I undertake as City Infinity.


Visualisation of a walking & cycling underpass.

While AutoCAD and the professional versions of NanoCAD (plus lots of other competitors) are very powerful and come with all sorts of clever modules, for sketches of junctions and layouts something basic is fine. The professional software is so sophisticated that from a highway engineering point of view, 3D models can be built of schemes and lots of changes made where the impacts and clashes can be tested - this is the world of Building Information Modelling (BIM) which is pretty much as much a mystery to me as basic CAD was for the designers who used to ink acetate sheets.

What is very useful about CAD is the electronic models we create are based on a coordinate system and so are very much recreate a little piece of the world in our computers which can be manipulated, measures and experimented with way before we thing about sticking a shovel in the ground.

My other medium is a pencil and paper with some ink and colour following on. At school, I studied craft design and technology (CDT) spread over two GCSEs covering Design & Communication and Design & Realisation. The first was very much about getting ideas across and the second were transforming those ideas into something tangible. Maybe the two themes have stuck with me. Drawing and sketching had been in my background for years, but with CAD, it was often a skill that wasn't topped up.

More recently, I have been in a position where I am (amongst other things) responsible for generating options and ideas to solve problems rather than having to do all of the clever (and sometimes laborious) task of converting thoughts into proper drawings that can be used to build things. Having said that, because I have been immersed in the practicalities of building things for years, I think I am reasonably accurate (and a scale rule helps in this regard).

I'm going to spend the rest of this post showing you a few sketches and describing what is going on and how the solutions would work. I have removed any local references, but if you realise where these are, I won't be responding to any questions on location! Sketching is a good way of getting ideas across without having to spend hours drawing it up accurately, although that assumes the sketcher has an idea that things will fit!


The problem being solved here was how to collect and connect eastbound cycle traffic to an existing two-way cycle track on the southern side of a street where the two-way cycle track also met a side street. Westbound cycle traffic from the existing cycle track met the side street and turned left from that. 

The idea here was to pick up eastbound cycle traffic with a one-way parallel signalised crossing which would run with an existing signalised pedestrian crossing and so give access to the existing 2-way cycle track. To reduce conflicts at the side road, I thought that making it a left out would help. In this situation, we'd often see cycle traffic being pushed onto a section of shared-use path to access a toucan crossing, but doing it this way means that we can use cycle detection for the parallel crossing and if we're careful, the angled crossing means we should be able to accommodate non-standard or adapted cycles.


Swapping between with-flow and two-way cycling is an issue that is always coming and and so making the swap within signalised junctions or at signalised crossings is a useful way of making the transition in a relatively safe way and as I mention above, we can use detection. The sketch above is pretty wild because it's where a dual carriageway becomes a single carriageway. Not only that, the single carriageway goes over a bridge which hasn't space for any protected infrastructure (pedestrians have a parallel footbridge on the south side).

The problem here was how to end a potential two-way cycle track at the bridge while giving people some sort of protection while crossing, because the prospect of a bridge rebuild was a very remote proposition. The two-way to one-way was dealt with using a parallel crossing as this would give people walking a route to the footbridge too. On the north side, eastbound cycle traffic gets an early start to get people ahead of traffic and hopefully into somewhere safer on the other side (a cycle gate). Eastbound cycle traffic would have a cycle gate to cross the bridge and then a jug-handle arrangement to line them up with the crossing. A complex bit of head-scratching when you really want a new bridge!


Above is a simpler sketch. This was used to explain to the team how we could work up a standard detail for a continuous junction treatment using entrance kerbs and blister paving at the threshold of where visually impaired people might experience traffic crossing. The team involved have now proposed an increasingly large number of this for many clients!


Above is an interesting one. The site is quite a busy signalised T-junction with a small side road off to the southeast (at the bottom of the sketch). There are cycle tracks in the area, but provision at the junction is n't that great. The strategy here was to simplify things (which is always a good thing to do where possible) by making the end of the little side street for cycle traffic only. 

The main T-junction gets a half-Cyclops junction on the western side (top of screen), but in order to maximise connectivity and to accommodate how people would behave at the side street, the southern cycle crossing point (to the left on the image) is actually two-way. In reality, we tried to develop this further, but some of the swept paths for larger vehicles became very challenging and so we'd probably have to reduce traffic lanes on the main road on which the jury remains out.


Above is a sketch I used to explain the implications of different ways of retrofitting cycle tracks in cross section. 1A is an existing situation, 1B is the same, but with a utility pit. 2 shows a carriageway level cycle track with 3 showing the problem that utility pits create. 4 in a stepped cycle track where we might be able to lower the covers to a utility pit and 5 is a footway level cycle track with a demarcation block where we can't adjust the covers to a utility pit. I was trying to explain that even if we tried to go with one strategy, we might need to adapt to local conditions. 

In the UK, we seem very reluctant to go for complete street rebuilds because this puts the overall cost up and therefore reduces the benefit to cost ratio which, unfortunately, weighs heavily with funders. Retrofitting, therefore becomes our default position.


Above is a series of options for picking out cycling space within a much larger pedestrianised area. Top left is basically do nothing and not worry about it too much and bottom right is push a stepped cycle track through the space. The others are somewhere between the two. There is no universally right or wrong answer and solutions will vary with place. This sketch was there to be provocative to get a discussion between engineers and landscape architects going.


The sketch about is almost meaningless without street names, but it was essentially an exercise in trying to unravel driving and cycling networks. The black lines are driving movements and the green are for cycles. Where the lines are close, this means cycle tracks. You can also see a couple of streets being filtered for cycle access or streets left which would be quiet enough for two-way cycling. Having a look at the network and developing a network design strategy is something we don't do enough, but trying to simplify things pays dividends when we move to junction design strategies.


Above is a pretty simple sketch showing a footway (orange), a carriagway-level cycle track protected by 0.5m bolt down kerb units and car parking spaces floated out (complete with me messing up the bay markings). I used this sketch to show how a fairly simple retrofit could be set out.


Finally for this week's post, above is a sketch of a cycle track running through a cross roads. The original layout prioritised east-west traffic, despite the north-south movement being busier and so as a result, there's a history of collisions. A scheme to add a two-way cycle track through the junction served to complicate things. I would have preferred to have made the two side roads one-way for general traffic away from the junction to reduce the complexity, but narrowing them to provide buffer space from the cycle track should slow things down.

The general traffic priorities are switched because the side roads are quieter, but we wanted to prioritise cycling so I added a parallel crossing because in the local context, it is probably more appropriate than adding signals, plus crossing design guidance is more flexible with zebra crossings being near side streets than signals (although I have taken some liberties). 

So there you go. I have rediscovered sketching and I'm increasingly enjoying getting by pencil, pens and paper out to play around with some ideas and to generate discussion. It's certainly something I'd encourage designers to try to do a little more, because even though it might not be as pretty as a CAD plan, I think there is something more human about it which helps to get ideas across.

I shall leave you this week with the revelation that this, my 473rd post also brings me neatly to my 9th anniversary of writing this blog which I couldn't comprehend would happen as I pressed publish back this time in 2012!

Saturday, 20 November 2021

Go With The (Contra)Flow

I had cause to dust down some of the older guidance and research on contraflow cycling in one-way streets this week and I think it's useful to throw it open to a wider audience.

The earliest reference I have for contraflow cycling is in the Bicycle Planning Book (1978, Mike Hudson) which has a drawing showing a mandatory cycle lane being used as a contraflow (below).

A diagram showing a street where general traffic (including cycles) can travel one way, but only cycles can travel the other. The contraflow for cycles is a while line with matching signs.

The layout uses a "plug" in the end of the street where cycle traffic can enter, but general traffic cannot. The plug is a traffic island where cycles pass left (there's a blue mandatory cycling sign) and general traffic has a no entry. At the other end cycle traffic gives way to the other main road.

Photo of a junction plug. There is a traffic island which allows cycling to the left wit no entry signs to the right.

Above is an example of a plug which leads to a contraflow mandatory cycle lane and below a street with an oncoming mandatory cycle lane.

One way street with an oncoming contraflow cycle lane.

Many "plugged" junctions you see look quite old fashioned in terms of space an accessibility. This is mainly down to the older traffic sign rules which did not permit a cycle exemption to the no-entry which meant the island with a cycle bypass was the only legitimate way to introduced such an arrangement. If you've some decent space, a plug is quite useful to stop drivers leaving the side road from cutting there corner where cyclists might be entering.

Another photo of a plugged junction.

The photograph is another example of a plugged junction, although in this case the road beyond is actually two-way for all traffic and is so known as a "false" one-way. At a higher level, we've been able to do things like this a long time. Traffic Advisory Leaflet 8/86 (which I cannot find a copy of) was a case study of a plugged junction in Meymott Street, Southwark. This is now just a piece of history as the junction has been fairly recently changed to a "no entry except cycles" arrangement.

Traffic Advisory Leaflet 1/89, Making Way for Cyclists, includes a diagram of a mandatory contraflow cycle lane (below) with some accompanying commentary. Interestingly, the contraflow one-way sign is referenced as "WBM 653.1". This is a variation of diagram 653 which was the reference of a contraflow bus lane at the time. WBM means "Worboys series B - Metric" with Worboys being the commission with standardised UK traffic signs. In other words, it wasn't a standard sign and would have to have had a traffic authority make an application to the DfT for a Special Authorisation to use it. In other words, more work to provide for cycling.

Diagram of a contraflow cycle lane in a one way street.

It's often hard to find early guidance (at least online), but in 1996, Cycle Friendly Infrastructure was published by the Bicycle Association with the Cyclists Touring Club (now Cycling UK), the Institution of Highways & Transportation (now CIHT) and the Department for Transport. There was an guide from IHT in 1984, but I've so far not found a copy. The sketch below is of a plugged junction and the text which accompanies it says;

A sketch of a plugged junction

11.4.1 Advantages and disadvantages. Cyclists can be seriously disadvantaged by one-way streets. They Introduce additional distance, delay and often hazards at intersections where weaving and non-standard road positioning is required. Vehicle speeds also tend to increase. Arrangements that permit cyclists to use streets in both directions can redress this situation and give cyclists a positive advantage over other traffic. The need for contra-flow arrangements will sometimes be apparent from cyclists disregarding one-way orders. 

The safety record of contra-flow lanes and other arrangements is generally good as there is good intervisibility between cyclists and oncoming vehicles (Werele 1992). A conclusion of the European Greening Urban Transport project, based on the experience of many towns and cities, is that in almost every case it is possible to exempt cyclists from one-way street regulations.

A Dutch street with a no entry expect cycles sign

Contraflow cycling in a Dutch Street

11.4.2 Contra-flow cycle lanes. A contra-flow cycle lane should ideally be at least 2m wide, but where road widths are restricted it can be a minimum of 1.5m. A mandatory lane is marked by a solid white line (1049) with signs (960.1). Waiting and loading restrictions on the contra-flow side are needed. If this is not possible, parking /loading bays should be marked and width should be allowed for car doors opening. 

A coloured surface is desirable. The with-flow lane may be as little a 2.5m wide depending on factors such as traffic volume, speeds and goods vehicles. In circumstances where oncoming vehicles may occasionally need to encroach on the cycle lane to pass parked vehicles, an advisory contra-flow lane may be used.

The first paragraph of the text is key because where we want to enable people to cycle, we should be making every street possible accessible and so a combination of one-way loops for general traffic and two-way for cycling can both remove through traffic to make streets quiet enough for people to just cycle in the carriageway, but not to the disadvantage to maximum cycle access. (The text is essentially what TAL 1/89 was saying).

A German street with a no entry except cycles signs

Contraflow cycling on a German street

In 1998, the Transport Research Laboratory (now TRL) undertook some research into contraflow cycling provision in its Report 358, Further developments in the design of contra-flow cycling schemes. The research looked at several existing sites which had varying conditions and through the use of video analysis and interviews with cyclists sought to try and put some numbers into what works. The executive summary says;

Contra-flow cycle schemes have been operating satisfactorily in the UK for many years. Most of these involve a mandatory contra-flow cycle lane and segregation at the entrance and exit. However, the number of contra-flow schemes installed has been quite limited, particularly when compared with certain other European countries. This appears to be due to the difficulties of implementing conventional contra-flow schemes, and a largely unfounded belief that contra-flow cycling is dangerous.

Some of the sites used the "no motor vehicles" restriction at one end of the contraflow systems which is slightly odd, but I think these situations didn't have enough space for plugs. I'm not quite sure on the prevailing legalities of the time, although the report does talk about Special Authorisations. It probably doesn't matter too much as some of the locations are so narrow, drivers can only travel one-way anyway.

The conclusions from the research are manifold and so it's worth having a read yourself, but for me, the following are most eye catching;

  • Many cyclists travelled illegally against the one-ways prior to the schemes being implemented and after that, cycle traffic grew.
  • There was no evidence of cyclists being put into significant danger by drivers.
  • Motor traffic flows and speeds were generally low, but excessive speed was a concern of cyclists (subjective safety in other words).
  • Even under the illegal behaviour scenario, there were no casualties amongst cyclists for 15 years before schemes were implemented and none recorded after.
  • Cyclists generally felt safe and this was in all types of situations of narrow carriageways, all sorts of kerbside activity, high numbers of pedestrians and with low and high cycling flows.
From a policy point of view, the general suggestion is essentially roll it out everywhere, including places which gives cyclists an alternative to hostile gyratories and roundabouts. In terms of numbers, TRL suggested;
  • Traffic speeds over 30mph or flows over 1,000 vehicles a day will generally need segregation.
  • Low traffic speeds and flow make this approach good from a cost, aesthetic and practicality points of view.
  • It works in narrow streets (or effectively narrow streets - i.e. space taken by car parking). Even short sections of 2.5m wide work fine.
  • Cyclists and drivers are looking towards each other and although driver speed might need managing, this is a good safety feature.
  • Drivers coming out of side streets and not realising there is two-way cycling is the greatest safety risk.
  • Parking and loading can be an issue and might need managing.
  • Cyclists preferred clear signage and road markings.
There is also a Traffic Advisory Leaflet which summarises this research; TAL6/98 Contraflow Cycling. The TAL refines the advice a little and gives more nuance (and much more advice). Some key options are;
  • Mandatory cycle lanes are needed if protected space is needed for cyclists at all times and where parking and loading is banned and where drivers won't be encroaching into the lane.
  • No cycle lane is needed if 85th percentile (driver) speeds are under 25mph and vehicle flows are under 1,000 per day; or the street forms part of a 20mph zone.
  • Advisory cycle lanes are needed if either 85th percentile (driver) speeds are under 25mph or vehicle flows are under 1,000 per day
We then fast forward to 2016 where we have the Traffic Signs Regulations & General Directions 2016 which finally do away with the general need for plugs because we now get a "no entry, except cycles" exemption (below) which is much more in line with many other European countries.

A one way street with a no entry sign with an "except cycles" sub plate

Of course, the "no entry, except cycles" isn't going to be appropriate everywhere, but it is a useful tool.

Finally, in 2020, Local Transport Note 1/20 Cycle Infrastructure Design was published by the DfT and Section 6.4 talks about contraflow cycle lanes. This is slightly confusing because the advice on contraflow cycling without lanes is elsewhere and maybe contraflow cycling as a subject could have been kept together. The key paragraph for contraflow cycle lanes is;

6.4.23 Contraflow cycle lanes should normally be mandatory, although an advisory lane may be considered where the speed limit is 20mph and the motor traffic flow is 1,000 PCU per day or less. The entrance to the street for cyclists in the contraflow direction should always be protected by an island to give protection against turning vehicles (see Figure 6.25) where traffic speed and flow is higher.

For situations without lanes, Section 7.3 covers it and suggests;

7.3.4 Permitting contraflow cycling in one way streets and using point closures to close certain streets to motor vehicle through traffic will generally provide a more direct route for cyclists and should always be considered. On quiet low speed streets, there may be no need for a cycle lane (see Figure 7.4 and Section 6.4), enabling cyclists to use narrow streets in both directions. Where there is good visibility cyclists and on-coming drivers should be able to negotiate passage safely. Contraflow cycling should be signed in accordance with the advice in the Traffic Signs Manual.

The Scottish Government's 2021 Cycling By Design document also covers contraflow cycling, but it seems more cautious than LTN1/20 and gets a bit more prescriptive on general traffic lane widths and not really anything about not having cycle lanes. for example, the guidance suggests a general clear traffic lane width of 3.0m to 3.2m. Once you introduce a cycle lane (say 1.5m to 2.m), the implication is going to be that in many situations, car parking is going to have to be cleared out. 

A narrow street with contraflow cycling and no lanes, just traffic signs.

A narrow street with car parking on both
sides with contraflow cycling

In my view, both sets of guidance miss the TRL research nuance (LTN1/20 in terms of structure, but most especially the Scottish guidance) and inexperienced designers will miss some of the site specific issues. This risks situations where the guidance will be used to "show" that contraflow cycling cannot be used in a situation were the alternatives are those situations TRL are saying they can avoid. The other point to make here is there will be plenty of streets in the same town or city where such discussions are had which still allow two-way driving!

The Welsh Active Travel Act Guidance, 2021, also covers contraflow cycling and has nice data sheets in Appendix G which sets out criteria, dimensions, flows and useful tips for segregated contraflow cycle lanes and unsegregated contraflow cycling. For my mind, this might be a little more helpful for inexperienced designers.

For me, I think the general approach for streets which are not gyratories or dual carriageways should be to have 2-way cycling by default. If there are situations where there are speed and/ or volume issues, then start adding the engineering which could be filtering (which is probably the right approach in many cases) and then cycle lanes or tracks which might need parking and loading dealing with.

One of the best approaches I have seen is in the London Borough of Lambeth. The council commissioned research to look at its one way streets to see how they could most practically made 2-way for cycling. Based on a series of attributes, the consultants proposed five categories of street;
  • Group 1 – No formal cycle lane required.
  • Group 2 – Segregated contraflow cycle lane advisable.
  • Group 3 – Mandatory contraflow cycle lane advisable.
  • Group 4 – Advisory contraflow cycle lane advisable.
  • Group 5 – Two-way cycling not advisable.
The idea was to take this output and use it for a programme of upgrades to enable 2-way cycling as much as possible. Interestingly, the list of Group 5 streets were just three. Two were extremely narrow and one would have had an "unacceptable" loss of car parking to make it work. The really narrow one, Randall Row, could actually be pedestrianised in my view!

The lesson from Lambeth and other places which have seriously looked at this issue is having a logical and systematic approach is a good one and even if all one-way streets cannot be made 2-way for cycling immediately, there are probably very few situations which cannot and maybe they are the ones needed more detailed consideration. In any case, the technique has been with us for over 40 years and so is nothing new and shouldn't be contentious.

Saturday, 13 November 2021

A Tale of Two Zebras

This week, I headed out on my bike again on a longer ride to blow the cobwebs today and as is often the case, I go out with a destination in mind. This time, I had a couple of zebra crossings I wanted to have a look at.

First is over in St John's Wood High Street in the City of Westminster, just to the west of Regent's Park. The reason I wanted to look at the zebra crossing here is because Westminster City Council decided that we need zebra crossings which look like stepping stones, thus copying others which have been installed in other countries.

A photo of the zebra crossing from a driver's point of view where the white stripes have shaded grey markings next to them to look like floating boxes.

Here is the crossing just south of the junction with Wellington Place (above), which was installed in early 2019. As you can see, the white stripes of the crossing have grey blocks around them to create the effect - except at that distance, about 15 metres, the effect doesn't quite work. No, you need to be right on it to actually see it.

Same crossing, but photograph taken from the driver's point of view almost at the crossing.

The photograph above was taken at about 5 metres from the crossing which is where one can see the effect which is, more or less, a series of 5 coloured blocks which kind of look like they are in the carriageway and you have to be in the centre of the carriageway to see it! From a pedestrian point of view (below), there are no boxes, just stripes which don't quite look right.

The crossing viewed from the footway.

So why was the crossing done this way? As best as I can work out, the crossing itself was installed to allay a local resident/ school safety concern and Westminster City Council said; 

"said the design had "been proven" to make roads safer, with one similar crossing in New Delhi, India, leading to average speeds dropping from 31mph (50kph) to 19mph (30kph)."

Cllr Tim Mitchell, the local cabinet member was reported as saying;

“Our 3D zebra crossing could be the future of road safety across the country and once again Westminster City Council is at the forefront in innovation in bringing this type of crossing to the UK.  

“Far from being simply a brilliant innovation that makes the ordinary look eye-grabbing and modern – the 3D effect helps drivers to see the crossing easier.”

The claims about New Delhi have been reported locally as having come from the local police, but in a more detailed news report, the claims are a little different. Speeds from people driving smaller cars reduced by a minimum of 1.6% whereas HGV drivers slowed by a maximum of 20.3% because they sit higher up where the effect is more obvious. I have had a search and I haven't found any academic or official paper behind the claims, but of course I would be interested to read anything.

The St. John's Wood crossing was apparently a 12-month trial, but I can't find anything published by the Westminster which has added another two of the same type. What can't be ascertained is if the 3D effect is impacting on driver speeds because as a new installation, there is no base data with a standard crossing. In any case, the road markings associated with zebra crossings are prescribed and this 3D effect could be argued as unlawful. 

The other problem with the crossing is the tactile paving. Zebra crossings should have red blisters in an 'L' shape. Here we have light grey without the stem of the 'L' which is how some visually impaired users orientate themselves. With the footway being light grey, the tactile paving doesn't show up well. The crossing is in a conservation area which does have a relaxation on colour in the guidance, but the tactile paving should at least provide a contrast to the paving.

Here's a quick video of the crossing;


Frankly, it's a gimmick which doesn't seem to have much science behind it. If you want people to drive more slowly over a zebra crossing, then build it on a road hump.

The other zebra crossing I had a look at is 8.3 kilometres to the southeast at the edge of Whitechapel at the junction of Cable Street and Sutton Street on London's C3 Cycleway (formerly CS3). C3 is a 2-way cycle track which runs on the northern side of this section of Cable Street. In fact, the layout predates CS3 as you can see on Google Streetview in June 2008;

A Google Streetview image of the junction with a green cycle track in June 2008

As you can see above, cycle traffic had to give way everywhere and the urban realm is bleak and pinned in by guardrail. Under Johnson's Mayoralty, the existing cycle route was painted blue and some layouts were tweaked including this junction as you can see on Google Streetview in August 2014 where the layout is simplified, the cycle track is placed on a road hump, but cycle traffic still gives way;

Same junction with some changes and a blue cycle track in August 2014.

Changes to the junction were proposed in early 2018 and by the Autumn of 2020, priority was given to people walking and cycling across Sutton Street. As you can see in the photograph below, C3 now has a parallel zebra crossing over Sutton Street and it is drivers who now give way as they turn right into and left out of Sutton Street.

A parallel zebra crossing over Sutton Street. To the left, the blue cycleway crossed with pedestrians to the left.

Both the cycle and pedestrian parts of the crossing are nice and wide with the geometry for drivers being nice and tight.

Another view of the crossing.

As has become the fashion, the space used to set turning drivers off the crossing is filled with some incidental rain gardens to give a completely transport little bit of urban realm. Personally, I don't like the blue surface colour, but the scheme matches what was there before. I prefer the gentle red of Old Bethnal Green Road elsewhere in Tower Hamlets.

Another view of the crossing showing little rain gardens either side.

The other thing I would change is the kerbs running across the cycleway. This section of C3 has quite a lot of them and many have failed. The transition between a cycle track and a carriageway should be asphalt to asphalt. That aside, it is so much better and is the standard that this type of junction should be.

I'll leave you this week with a little video of this crossing;



Saturday, 6 November 2021

WRAT Run

Walking is both ubiquitous and hidden - a mode that most people use, even it's just a little bit and we've walking networks everywhere (at least in urban areas), but at the same time it's forgotten at the margins.

How can we raise the mode's profile in an increasingly crowded public discourse? Well I think that using some of the audit tools available to us is a very good place to start because unless we can measure something, it's hard to articulate how something could or should be improved.

People walking in the pedestrianised part of Winchester City cenre.

Walking is something we just do and take for granted.
(Winchester City Centre)

In England, walking accounts for 5% of the distance people travel, but it accounts for nearly a third of trips and so we are talking about it being firmly about local trips. The Pandemic has reduced the number of overall trips people make, but walking locally has remained high and important for all of the good reasons of it being cheap, easy for most people, low carbon and good for overall health. When I refer to walking, I need to be clear that this includes people using wheelchairs or mobility scooters and pushing prams and buggies.

Walking as a mode is a devolved matter in national policy terms and ultimately, the management and improvement of walking networks rest with highway authorities, although district, parish, town and community councils have limited local powers. This fragmentation means that local custom and practice has evolved, walking will have different local political priorities and getting consistency challenging.

Auditing is a way of using a consistent approach to measure the quality of the walking environment. There are lots of systems and approaches out there such as;
There are also other tools which look at wider issues, but include walking such as;
Personally, I like the Healthy Streets and Place Standard tools and some authorities have variations. However, for user-friendly and quick assessments which anyone can pick up and just use, I'll go to the WRAT every time.

WRAT has its origins in the Wales Active Travel Act Guidance and is used to help develop active travel network maps for the country. There are a range of tools which professionals can use to undertake audits and then to use them to help shape delivery programmes and priorities. However, I am going to concentrate on the WRAT which is a spreadsheet-based system. 

The original Welsh spreadsheet is here, and it has also essentially been co-opted by the Department for Transport in the English Local Cycling & Walking Infrastructure Plans Guidance, here.


Extract from the DfT version of WRAT

The spreadsheet is split into five themes which won't be a surprise to many of you, because they are the same five themes for good cycling design;
  • Attractiveness
  • Comfort
  • Directness
  • Safety
  • Coherence
Under each of the themes, there are items which can be scored. Attractiveness deals with the maintenance condition, fear of crime, traffic noise and pollution, plus anything else which might be appropriate to the location. Comfort is about having level footways without trips, a good width for the situation, a lack of footway parking (or at least a decent width left), plus an "other" line.

Directness is about desire lines being cater for in terms of footway routes and crossings, ease of crossing the road, sufficient green man time and an "other" catch-all. Safety is around traffic volumes and speed with good visibility. Coherence looks at having appropriate dropped kerbs and tactile paving.


A desire line over an urban dual carriageway. This is
where people want to cross and even though it is so
hostile, people are prepared to cross because it is direct
and far preferable to other options.
(Romford town centre).

In terms of assessment, the spreadsheet is used to score each street or section of street (as you see fit) as a 2 (green), 1 (amber), 0 (red). The Wales WRAT has space to record critical issues and to give a revised score to suggested improvements. The DfT version is simpler with space for comments and suggested actions. There are a total of 20 things to assess which means a maximum score of 40 points. In the Welsh experience, sites which score at 70% or better (28 points) is taken as suitable to include in local network maps with other sites needing work and this was taken on board by the DfT version.


You might want to chop long streets into sections
and assess large junction separately. It's up to you which
makes the WRAT a really accessible tool.

For someone undertaking an audit in their community (and especially if you are not a professional), the DfT version is simpler. If you are using WRAT as a campaigner you can of course make suggestions for improvement, but it's not your job to redesign a street for the highway authority - people are paid to do that after all!

What is nice about the WRAT is it's scalability. You can use it for your own street, you can chop up a long street into sections, or you could concentrate on a junction if you wanted to. I have used it for quick assessments where I've done a rough and ready review of an area (such as a business park) on a street by street basis using Google Streetview to give a starting point to more detailed conversations and work.

One thing which is missing is a summary sheet and so what I like to do is have a WRAT sheet for each street or section running in my workbook which scoring summarised and linked to a summary page. Here's an example of what one can do, in which I have used the Welsh 70% threshold for "green" and 60% for "amber",


There are limitations to WRAT. It won't give you the granularity that some of the more sophisticated approaches and of course it doesn't cover the wider things we need to cover in street design and management. However, it doesn't matter because it is aimed at developing network assessments quickly and we can come back and look at things later.

So, it might be helpful for a little bit of a worked example and so I have picked a nice controversial street to score - Exhibition Road in London.


Exhibition Road. A so-called "shared space" scheme.

I am going to have a look at the section between the junction with Kensington Gore and the junction with Cromwell Road. I'll take this as one complete assessment rather than breaking it down because of brevity, but within about 30 minutes using Google Streetview, a bit of my own experience and a local authority report, I have scored the street at 26/40 (65%). With my summary table idea, this would an "amber" score and one could plot this on a map if the wider area is being looked at.
  • My summary scores are;
  • Attractiveness - 5/8
  • Comfort - 10/12
  • Directness - 8/12
  • Safety - 3/6
  • Coherence - 0/2
You might not have access to traffic flow or speed information and so you'll have to come to a view in many cases (or maybe do a bit of survey work yourself. From the scores, you can also see how things tend to be weighted towards comfort and directness. Everyone will have a view, but it's a tool to compare like with like.

In terms of comments on what could be improved, it would be to significantly reduce motor traffic on the street, provide much clearer tactile paving at formal crossing points and a bit of speed reduction work. Addressing these to items would maybe get the score up to 32 (80%) and maybe reflect the southern end of the street which is filtered from through traffic (below).


If you want to look at my example in detail, then you can download a PDF here. Of course, you are allowed to disagree with my assessment! Anyway, have a look at a the tool and have a go yourself.