Urban Update 26 Feb 2016 - Why are cars and lorries the starting point for street design still cars and lorries and not people?

Download Urban Update 25 Feb 2016

Why is the starting point for street design still cars and lorries and not people?

Turn to any street design guide and you will find a rich and generous amount of information vehicles, such as how big they are, their rates of deceleration the distances they take to stop, and the path they follow when they turn a corner, and what sort of street design is needed to make them happy.  Look for information of similar depth and detail on children, or elderly people, or people in general, and you will be disappointed.  Unanswered questions include:

  • What are the typical walking speeds of people?
  • How long does it take an elderly person to cross a 7 metre wide street, or the 20 metre wide mouth of a side road built with 15 metre radius kerbs? 
  • How long will it take a wheelchair user? 
  • How long does it take a pedestrian to judge whether there’s a gap in the traffic sufficiently long that it is safe to cross the street? 
  • How often do they make errors – such as looking but not seeing? 
  • What sorts of injuries do pedestrians sustain at what sort of impact speeds? 
  • What noise levels start to make people uncomfortable? 
  • At what level of street noise does conversation become difficult?

There are many more questions that can be asked, and there is plenty of research available that answers them.  But very little of it appears in the guidance documents at national or local levels. 

Local street design guidance is the product of a roads and vehicle based evolutionary tree that that goes at least as far back as the 1930s.  In the UK there have been landmark publications such as theDesign and Layout of Roads in Built up Areas (1946), the Design Manual for Roads and Bridges,Roads in Urban Areas, Traffic in Towns (1963), and Design Bulletin 32. – Residential Roads and Footpaths (1977).   The giveaway is in the words used in titles… “roads”, “traffic”, “residential”, “urban”.  Words such as “children”, “blind people”, “elderly people”,” men” and “women” are absent.   Certainly the guides and standards have evolved, and certainly the authors over the years have been concerned about deaths and injuries.  But the overriding focus has been design for traffic and vehicles, with people, landscape, and all other issues fitted in around the edges.

It is time to break this evolutionary chain, and produce street design guides with people genuinely at their heart.  There should be detailed, researched based data on human needs and capabilities.  Above all else, the visions and guidance must be carried through into specifications and technical design.  Without this, the aspirations for people focussed streets and settlements will appear only on paper.

 

Roads to places - Integrating green and grey infrastructure for highways design

TDAG Workshop report - Nottingham 17th February

The 8C’s Design Guidance is being developed by a consortium of councils, (6 originally: Derby and Derbyshire, Leicester and Leicestershire, Nottingham and Nottinghamshire)   To improve the content on trees and landscaping, a workshop was organised by the Trees and Design Action Group, with support from the UDG, and attended by over 60 practitioners.

Most people instinctively appreciate trees.  There is evidence that our brains are hard-wired to respond natural green environments, and in towns and cities there is no finer example than healthy, established trees.  However it was quite clear from the meeting that trees are regarded as a “bit of a problem”.  They cost money to introduce and maintain, and cash strapped highway engineers get concerned about disruption to utilities, breaking up of footways, and leaf litter.  There needs to be a good amount of thought in designing them into a street too, and it is so easy to eliminate them from a design, by cost cutting or sheer laziness. 

The event spent a lot of time on the practicalities.  There’s no point in drawing green blobs on masterplans if there is no way to provide the necessary conditions in which trees will thrive.  The result will be dead trees, and disappointed residents.

Tree roots need air and water so that they can exchange carbon dioxide and oxygen with the atmosphere.  Compacted or waterlogged soils will lead to stunted growth or death.  Latest techniques for street tree were outlined:

  • Continuous trenches – most cost effective
  • Load bearing systems

o   Raft systems

o   Crate systems

o   Structural soil (ie stone/soil mix)

It is important to choose the right tree for the right location.   Big trees are great, but many small trees are also of value – and it is value that can be estimated using programmes such as i-tree.

There needs to be room for trees and this links with parking design and the work pioneered in “Space to Park” which is probably the UK’s leading best practice guidance.   The residents’ post-occupancy studies on new development that underpinned the Space to Park (undertaken by Bob White whilst he was at Kent County Council) found that residents don’t like narrow streets, get seriously stressed about parking issues, and would rather park their car in front of their house where they can keep an eye on it.  On-street parking minimises land take, minimises run-off by eliminating unnecessary areas of hard surfacing, and the extra street width can be used to plant trees and other landscape features such as rain gardens.  The demand for parking in turn is influenced by the location of the development and the quality of the walking and cycling routes, and public transport.  It is not surprising that one of the main messages from the meeting was for integrated design and integrated infrastructure

Commuted sums, turned out to be the elephant in the room.  Local authorities were reported to be asking £800, £1500 even £2500 for each tree.  This tree tax can have grave consequences on the quality of the development. 

Trees are a benefit – not a problem!   They shouldn’t be taxed.

“Trees in Hard Landscapes” is currently the leading guidance on the subject and can be freely downloaded on:

http://www.tdag.org.uk/trees-in-hard-landscapes.html