1. Norman W. Garrick Lecture 3.2
Basics of Urban Street Networks
Norman W. Garrick Lecture 3.2

2. Impact of Street Network Design
Research shows that street network design can impact
Traffic safety
Choice of Mode
Vehicle Miles Travel
Health outcomes
Character and value of communities

3. versus

4. Risk of Severe Injury or Fatality* Chance of being Severely Injured
Safety Impact
Risk of Severe Injury or Fatality*
versus
Chance of being Severely Injured
30% Higher
Chance of being Killed
50% Higher
*Given that an injury occurred

5. Odds of Dying in a Road Accident based on Intersection Density*
Impact on Safety
Odds of Dying in a Road Accident
based on Intersection Density*
1 in 200
1 in 500
*Given that an injury occurred

6. Percentage of People Walking, Biking or Taking Transit
Impact on Mode Choice
Percentage of People Walking, Biking or Taking Transit

7. Impact on Mode Choice
Percentage of People Walking, Biking or Taking Transit
Effect of Intersection Density for Cul-de-sac Network

8. Impact on Mode Choice
Percentage of People Walking, Biking or Taking Transit
Effect of Intersection Density for Gridded Network

9. Why sprawl may be bad for your health
Their study* looked at 24 medium-sized cities in California, built at different times and with a variety of different street designs.
They then examined self-reported health data from the California Health Interview Survey, which sampled 40,000 to 50,000 adults in 2003, 2005, 2007 and 2009.
Their analysis controlled for socioeconomic status, commute times, the presence of fast-food restaurants and grocery stores and other land uses.
Ultimately, they found that higher intersection densities were significantly linked to reduced rates of obesity at the neighborhood level, and reduced obesity, diabetes, high blood pressure and heart disease at the city level.
*Marshall, Garrick and Piatkowski

10. Cul-de-Fat: How Suburbanization is Contributing to Obesity
Do We Look Fat in These Suburbs?
Just living close to Walmart makes you Fat

11. Features of a Good Urban Street Network
High Density of Intersections
The density can be measured by intersections per square mile or my block size or other related parameters
High Connectivity within Neighborhoods
Good Porosity Between Adjacent Neighborhoods
There should be good connections between neighborhoods. Not all streets should extend beyond neighborhood boundaries but most should. Streets that traverse multiple neighborhoods or even the whole city should be frequent (no more that ½ mile apart).
Great Variety in Streets Types
The street network should have streets that support a variety of land uses and social contexts. As such they should vary from very busy to very quiet, from mostly commercial to mostly residential. In general, the busier streets should be the more commercial and facilitate regional as well as local travel. While the more residential streets should be shorter and facilitate mostly local travel.
No Restrictions on the types of streets that are connected to each other
For example, small neighborhood streets should connect to big regional streets with no restrictions.
One-way streets are an example of restrictions on how streets are connected
The turn ROUTE MODIFICATION is used to describe types of restrictions that are frequently employed
All Streets should be walkable and crossable and multipurpose
All Streets should have building frontage

12. Good Porosity Between Adjacent Neighborhoods
Less Good Example

13. Good Porosity Between Adjacent Neighborhoods
Good Example

14. Factors in Creating Diverse Street Type
Great Variety in Streets Types
Factors in Creating Diverse Street Type
What are the factors contributing to difference between streets types?
Street cross-section design
Continuity of the street in the network
Type of intersection connection in the street network
Street alignment in the street network
Note that these are a combination of
Features of the street itself, and
Features of the street network.
The street design should complement the street network design

15. All the streets are the same in the network
No variation in the street type

17. Prenzlauer Berg – Regional Context

18. Prenzlauer Berg – City Context

19. Prenzlauerberg Berlin

20. The Streets of Prenzlauer Berg
Schoenhauser Allee
The main street
Prenzlauer Allee
The second main street
Pappelallee
A neighborhood shopping street
Raumerstrasse
A neighborhood shopping street
Goehrener Strasse
A residential street

21. Schoenhauser Allee The main street

22. Schoenhauser Allee The main street

23. Schoenhauser Allee The main street

24. Prenzlauer Allee The second main street

25. Pappelallee A neighborhood shopping street

26. Pappelallee A neighborhood shopping street

27. Raumerstrasse A neighborhood shopping street

28. Greigenhagener Strasse similar to Goehrener Strasse A residential street