Tuesday 7 May 2013


"All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, the fresh-water system, and public health, what have the Romans ever done for us?"*

London to Colchester was an important route for the Romans and
so they built the A12 and several retail parks along the way.
Let's cut straight to it, we know that the Romans were a dab hand at building roads in order to service, expand and control their Empire, and yes, they often built them straight (or straightish!). They were moving people and goods and saw the value of keeping it simple and serving the Empire's desire for efficient transport links. (warning, this post contains photos of shared-use cycle tracks which I know are not the best examples of infrastructure!)

The Romans didn't let hills and swamps get in their way, they pushed on through by digging or piling. Their main roads were paved; concrete was being used and they were built to last. Look across the UK, and their old routes remain on maps - "Roman Road".

So, what did the Romans do for us? They built their roads on the desire line, a concept which is very important when using leg power and is just as important today for those walking or cycling, but all too often ignored for the convenience of motor traffic.

Look at the packed down soil - people want to walk here.
This is a desire line in action and such a no brainer, you don't even
need to be an engineer to understand - hell, even a politician could

understand this one!!!
Put simply a desire line is where people want to go. It could be the line between home and work, or it could be very localised - you often see it in grass verges where pedestrians carve out a route in the mud showing where they want to walk. 

We engineers have made an industry of trying to stop people taking the direct route; OK, not all engineers, the politicians are also complicit and don't get me going on architects, planners and urban designers! It has taken decades to get here with guardrail, footbridges with switchback ramps, barriers on cycle routes, pedestrian crossings in strange places and dingy subways which nobody wants to use.

If you are walking and cycling, you are expending some effort to do so and being taken off the route you wish to follow is annoying for many, but it can be tiring for some users; and if it is that circuitous, then people will be put off from using the route completely (have you seen the dual carriageways in Birmingham?). Some will just find their own way through, even if it means taking a dangerous route (subjectively and actually in many cases).

Desire lines are not just about directness (although very important), they are also routes which people prefer to use even if the route is just a little longer that the direct desire line. Different users will have different needs and perceptions, but essentially, our aim should be to cater for direct desire lines and in doing so, they need to be safe (actually and subjectively), easy to use and intuitive.

The desire line for pedestrians is straight over to the street beyond,
but in the name of vehicle capacity pedestrians get half way across
this dual carriageway and are then sent to the right just beyond
where that chap is walking to cross the second half. You can often
see some people crossing to the left of the guard rail and dashing
right across on the desire line (on a Transport for London route).
Where busy road junctions are concerned, pedestrian and cycle facilities are almost add-ons. These junctions are designed to stuff as many motor vehicles through as possible and to hell with those not on four wheels.

This photo shows the classic "right handed stagger" at a large dual carriageway cross roads which is designed to maximise traffic capacity. Pedestrians cross the first half of the road and then have to turn right off the desire line to cross the second half. 

In the image, the crossing shown is at the stop line of the main road which means that the green man is displayed when the traffic stops. The traffic has to stop anyway because there are right turn filters and cross traffic flows running and provides no inconvenience to traffic. The second crossing is out of shot, but just to the right of the chap walking in the guard-railed central reservation (known as a sheep pen by engineers). 

This crossing is set well away from the junction so that when pedestrians get a green man, traffic coming out of the junction has stacking space away from the junction. The pedestrian phase would come in at the same time as the right turning filters (so no conflict) and then cross traffic which will be turning towards the crossing relatively slowly. Of course, pedestrians are kept waiting until the signals are ready for them and so often, they will just dash across in a gap in traffic flow, despite best efforts to guardrail the junction to within 25mm of its life.

This layout is a little more modern, but still prioritises traffic flow on 
the TfL trunk road over pedestrians and cyclists who want to cross
in one stage.
Here is another right hand stagger (Toucan this time), but in the side road. There is another one across the main road which is in the top right. 

Again, this is designed for traffic capacity as pedestrians/ cycles only get a green on each half at a time. The central reservation is quite narrow and so the stagger is meant to stop people going across in one go by mistake. There is no guardrail and so it has been accepted that some people won't bother with the formal crossing on the far side and will cross in traffic gaps on the desire line, although cycles will struggle with the kerbs! This is a very new layout for the junction and replaces a much worse layout (for pedestrians and cyclists) which was partially signalised meaning that many of the crossing points did not have green men/ cycles. 

The new layout also has the pedestrian/ cycle signals running on green when the right phase of traffic is held and so if you adjust you approach speed as a cycle user, you don't actually need to press the button. This layout would of course be better with a straight through single stage crossing, but being on a trunk road, TfL has decided to go with traffic capacity. This is a difficult one for me as I think it should be straight though, but I do understand the capacity argument - a classic decision and in this location, taking away traffic capacity would create a huge political and driver backlash - I think TfL has had to play the game here and has created a fair layout. Possibly in time, there might be another iteration where the balance goes more towards the non-motorised users.

It is not all about traffic signals. This photo shows a very simple change to meet the desire line. The red line shows where people were originally meant to walk - right into the access to the car park. Following conversion of the footway to a shared-use cycle track (which is not bad and much better than the 50mph dual carriageway!), this side of the crossing was widened so that people could cross on the yellow line.

This layout is better in a very subtle way. Previously, those crossing were hidden by the wall and advert sign (which is on private land). Drivers turning left off the trunk road could not see people crossing. This new layout allows people to see and be seen when crossing and puts them right on their desire line. Pedestrians and cycle users are not given priority because traffic turning left in would effectively have to stop on the edge of the high speed trunk road to give way which is very risky.

Actually, we could easily improve the layout further. When travelling in the opposite direction to the arrow, you need to check behind you for traffic turning left into the side road, which is not a perfect situation, especially when cycling. 

We could physically stop the left turns in, as the side road can be accessed from its other end with a little local diversion. We also need to allow people to leave the side road as deliveries and refuse vehicles cannot turn round in the side road and it is too far to reverse.

This alternative layout does not give 100% priority to pedestrians and cyclists, but in this case the side road is quiet and so the desire line is pretty much catered for. This example expands the idea of a desire line from being simply an issue of directness to an issue of priority, comfort and indeed subjective safety as well.

TfL needs to get it's tarmac lorry out!
In this photo we have a two-stage straight through Toucan crossing using near-sided signals - in other words, the red/ green man/ bike is on the yellow push button unit. 

This crossing is near a large roundabout with multiple dual carriageway approaches and with a fly-over for through traffic (TfL route again). It takes a shared-use cycle track over a pair of 2-lane slip roads and as the crossing isn't far off the desire line for the walking/ cycling route generally, people naturally use it. Cycling on the roundabout is the most direct and fun for nutters or at 6am on a Sunday, but these crossings cater for most people.

The central reservation is wide enough for people to intuitively realise that it is a two-stage crossing and the near sided signals mean that people are not being confused by seeing a green man in the distance intended for the other crossing (called "see through" and is an issue for far sided signals). 

Apart from having tatty surfaces, the one improvement I would make is to link the push buttons between both crossings so that you only need to push once. The traffic signal controller could take walking speed between the crossings into account and if all is well in terms of traffic approach speed/ flow (which is a safety consideration for all users), then the green signal could come in as someone arrives to cross the second side. Alternatively, detectors could "see" the demand and do the same - I have suggested this to TfL, but I think it has gone onto their "too hard" pile.

Pedestrians cross a convoluted network of dropped kerbs and
staggers and without green men to help them. Still, they can always
use the footbridge in the distance, so long as they can use stairs as
there are no ramps! Image from Google.
Here we have the junction of the A12 and Barley Lane which does very little for pedestrian desire lines and nothing at all for cycles. It is a fairly typical layout for a junction on an Outer-London TfL Trunk Road and similar layouts can be seen on the A10 and A205. The layout was designed at a time when throughput of traffic was the only consideration and so we have ended up severing communities in the process. We do sometimes provide subways on these main routes, but they can be quiet and lonely places, so people do not use them.

Oxford Circus. Image from Waterman Aspen. I am convinced that 
the buff anti-skid surfacing every where was only put in to make 
photos look good - it is not needed and is failing because of all the
vehicles turning on it in the junction!
This is Oxford Circus, which is the ultimate in traditional UK crossing facilities for pedestrians at junctions (other countries have had them for years and there were several in the UK before this one). Known as an 'X' crossing or a "Scramble" crossing, when the green man comes into play, pedestrians can cross in all directions and diagonally - you can see it in action here

The arrangement essentially got built because of domination of the space by pedestrians and so the footways were widened on the corners to give more waiting space and the diagonal crossings put in. This was to the detriment of traffic capacity, but tough - the pedestrians are most important mode here as it is the confluence of Oxford Street and Regent Street, both very important shopping streets in the West End. The area is also heavily used by buses and so some of the pedestrian green times are tight (assisted by pedestrian countdown) which helps mitigate traffic flows, although at Christmas, it is quicker to walk than ride on a bus in the area!

Oxford Street at Christmas - the buses are heading
towards Oxford Circus (very slowly!)
Back to desire lines! The green lines show the crossings roughly in line with the direction of the footways. They have the usual dropped kerbs, push buttons and tactile paving. The purple lines are also crossings with push buttons, but no dropped kerbs and therefore no tactile paving. 

The designers could not make the layout work with dropped kerbs on the diagonal crossings as blind/ partially-sighted people would be confused with complex tactile paving layouts. I understand that after extensive consultation with access groups, the now (fairly) famous layout was agreed.

So, how should we be designing for the desire lines of pedestrians and cycle users in the 21st Century? Well, for new street layouts, whether as part of a development or as part of a project to change existing streets, these desire lines need to be looked at first, with access or passage for traffic looked at second and then being designed around the pedestrians and cycle users.

Idea for a bus stop bypass on CS2 which maintains a desire line for
cycle users which is actually and subjectively safe. But, pedestrians
may be impacted when crossing the cycle track to get to and from
the bus stop.
Proposed schemes such as the extension to Cycle Superhighway 2 and the Mayor's Cycling Vision look to reallocate road space to protected cycle routes which follow desire lines for commuter routes.

We also have the Mayor's Quietways idea which seek to use quieter back streets for cycling which is fine to a point if the routes are direct and useful. Other bloggers such as Cyclists in the City have done a good job at debating the idea, but I think that the process should start with looking at the desire lines first.

This sign (and the 6 foot fence) is aimed at stopping pedestrians
from crossing the A127 
just outside Basildon. I wonder if the
question of why people want to cross there was ever thought about?
Image from Google.
It might be as simple as mapping existing walking and cycling routes, adding schools, shops and railway stations and then looking to join them up with direct routes where walking and cycling can be prioritised over traffic either completely or protected physically. It may mean engaging with existing and perhaps more importantly, potential users, to see what it would take for them to switch to walking and cycling. I think that care is needed to make sure that Quietways do not become a proxy for banishing cycle users to back streets so that main roads can be left (or even made more) unattractive for utility use so that traffic flow is prioritised - we need to watch out for this being sneaked in.

Here is a literal barrier on a cycle route. Take it out along with a
of sections of the fence and it is useable.
When planning routes, there will be barriers, but I think it is worth assuming they can be overcome in the first instance (i.e. stick to the desire line) and then spending more time looking at them in detail later. Barriers might be physical such as roads or rivers, may involve private land owners, acquiring land or political will where one might assume that a scheme will not get support. 

Local authorities can acquire land, build things, use legal powers, negotiate with land owners and use influence with planning applications. They also own parks and open spaces which can often provide more direct routes than the highway network. Organisations such as Sustrans are very experienced in helping to bring the right people together - their Connect 2 project has helped overcome many barriers on walking and cycling routes.

Sorry, had to put this image up again from the BBC News website.
This trial of a Dutch-style roundabout by TRL for TfL will allow
pedestrians and cyclists to negotiate roundabouts in a way which
may be off the absolute desire line, but will feel safe and therefore
acceptable to use, even if it takes a few seconds longer to cross.
No waiting for the green man/ cycle here!
I do think that things in this country have started to change as many people fall out of love with the car for various reasons. 

Harnessing the desire line and indeed the desire to move around in a safe and congestion-free environment must be part of the answer to civilising our urban spaces?

So, what did the Romans do for us? Well, perhaps they got the concept of constructing to desire lines into the brains of the ancient Britons, it is just that we have used it for traffic in the last 100 years rather than for people.

* From Monty Python's "The Life of Brian"

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