New advice, new principles

• Design quality
• High Density
• Strong urban form
• Mixed Use
• Low car dependence
• Personal security
• Traffic safety

Conflict with traditional principles of designing for traffic & personal safety

Issue 1: Permeable Layout or “traffic bundling”

Sandhurst, Cul-de Sac layout

Pros:

• Low traffic volumes at home
• Low traffic speeds at home
• Perceived personal security

Cons:

• Poor access on foot/cycle
• Encourages car use
• Insular households

Permeability or traffic “bundling”?

Permeable layout

• Spread the traffic load
• Convenient for local movement (short distances)
• Easy to navigate

But...

• Through (rat run) traffic

Grid layout is permeable

Santa Ana, California

Pros:

• Efficient access A to B
• Choice of routes
• Dispersal of traffic
• Legible network
• “Populated streets”

Cons

• Many cross streets
• All streets open as “rat-runs”

Too much permeability

Radburn-style layout

• No clear font and back
• “Escape routes”
• Low privacy
• Poorly used spaces
• No sense of “ownership”

What size of grid?

• Barcelona “Example”
• 100 metre blocks
  
• Portland.Oregon, downtown
• 30 metre blocks

Issue 2: Crossroad safety problems

Pimlico, London

• Grid must be managed
• Priority at crossroads
  
• Must show priority
• “Give way”

or

• Mini Roundabout

Priority at crossroads

Berlin

• Continent:
• Default priority from the side

Modified grid

Rieselfeld, Freiburg

• Grid layout

Strong linear form

Vauban, Freiburg

• Shared space
• But virtually Car-free

Modified Grid solution

Modified permeable layouts:

• Close sections of grid to motor vehicles (see picture)
• Provide bus only “gates”
• “Preferential routing” for buses and/or cycles

Issue 3: Frontage development*

(Anywhere)

• Distributor roads:
• Traffic priority
• Soulless place
• Lack of surveillance

Issue 4: How wide is good?

Wide roads can encourage speed
So narrow streets are advocated

• Speed can be managed in other ways:
  * Optical width
  * Frequent crossings, lights
  * Indirect routes
• Physical measures

Wide streets encourage speed…
but wide streets have more scope…

Oisterwijk, NL

…for all modes

Berlin

• Boulevard catering for
• Footway
• Trees
• Cycleway
• Parking
• Main road traffic
• Bus priority
  (where needed)

and can have more style

Lyon

and landscaping

Perth, WA

Narrow streets

Pros:

• Optical width reduces speed
• Maximum use of land

Cons

• Speeding to avoid oncoming vehicles
• Poor footways
• No “quality margin”

Where can you walk safely?

Cologne
Shared space:

• Parking anarchy?
• People insecure
• Visual mess

Parking determines design?

Tübingen

• I to 1
• Communal
• Public
• On street (in bays)

Parking plus good environment - at a price

Freiburg

• Undercroft,
• Basement

Modern “Home Zone”

UK

• Mews?
• or “service yard”?

Issue 6: Design priority

Chelsea
BEFORE

• Design for vehicle convenience

Chelsea
AFTER

• Design for people

Design for vehicle users

Louth, Lincs

• Large radii
• Sightlines

Design for people

Rieselfeld, Freiburg

• Tight radii
• Continuous footway
• No kerbs
• Low speed 30kph
• Landscaping

Conclusion

How can we resolve these conflicts?

• End litigation culture?
• Designers take more care with layout between buildings
• Planners take responsibility for traffic and parking advice
• Joint training of engineers, planners