"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.
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!!!
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.
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.
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.
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!|
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.
|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!
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!)
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.
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.
|Here is a literal barrier on a cycle route. Take it out along with a|
of sections of the fence and it is useable.
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!
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"