street networks: traffic safety, travel mode choice and emergency services
DESCRIPTION
Norman Garrick compares street network design from pre-1950 and post-1950, factors that help determine the overall safety of safe pedestrian travel, and explains why it is so obvious that the pandemic of sprawl development is to blame for unsafe, poorly designed, disconnected neighborhoods. Studies prove that Street Network Design has an integral role in providing safe, pedestrian friendly,and highly accessible communities. We must re-think the suburban model in order to reform emergency response.TRANSCRIPT
Davis, CA14 % of people ride to work
Davis, CA
Road Fatality Rate: 1 per 100,000
Road Fatality Rate for All 157 California Cities Over 40,000
number per 100,000 population
0.0
17.3
Road Fatality Rate for All 157 California Cities Over 40,000
number per 100,000 population
Risk of Fatality
(Fatalities as % of Injuries) California Cities of 40,000 to 120,000
Adapted from Stephen Marshall
Pre-1950’s Post-1950’s
Evolution of the Street Network
FHA Technical Bulletin No. 7 (1938)Planning Profitable Neighborhoods
According to the FHA the grid layout was
MonotonousHad Little CharacterUneconomicalPosed Safety Concerns
Street network, safety and sustainability in 24 medium sized California cities
Cities selected to represent a range of traffic safety level
Shape and Configuration
Network Scale
Network Connectivity
Citywide Street NetworkNeighborhood Street Network
Linear Tree GridTributary Radial
Grid
Tree
Adapted from Stephen Marshall, Streets & Patterns
550 Intersections per Square Mile
Network Scale
110 Intersections per Square Mile
Network Scale
45 Intersections per Square Mile
Network Scale
Link-to-Node Ratio = 1.61
Link-to-Node Ratio = 1.13
Link-to-Node Ratio = 1.16
Network Connectivity
Street Network Properties
Street Design Properties
Average Total Number of LanesAverage Outside Shoulder WidthRaised MedianPainted MedianOn-Street ParkingBike LanesRaised Curbs
Travel and Activity Level
Distance from City Center
Income
Mix of Land Use
Variables included in Our Safety and Travel Choice Models
Safety Analysis Based on Geo-coding 230,000 Accident Recordsin 24 California Cities
Safety and Travel Choice Analysis done for 1040 Census Block Groups 24 California Cities
Travel Choice Based on Census Data1040 Census Block Groups, 24 California Cities
versus
versus
SafetyRisk of Severe Injury or Fatality
Chance of being Severely Injured
30% Higher
Chance of being Killed
50% Higher
Odds of Dying in a Road Accident based on Intersection Density
1 in 200
1 in 500
Percentage of People Walking, Biking or Taking Transit
Percentage of People Walking, Biking or Taking TransitEffect of Intersection Density for Cul-de-sac Network
Percentage of People Walking, Biking or Taking TransitEffect of Intersection Density for Gridded Network
Thanks to
US EPA and CNU
28,000
14,000
8,000
15,000
11,000
14,000
11,000
8,346
10,52412,831
8,600
2,461
28,820
7,518
6,774
16,186
10,364
13,154
24,283
5,898
15,547
17,107
Davis: Response Time
14.9 mph
14.2 mph
12.7 mph
Downtown Hartford 1960 to 2000 Parking
City of Hartford 1960 to 2000 Population and Employment
Evolution of Network in California Cities
Norman W. Garrick
Norman W. Garrick
11 X
2 X
Norman W. Garrick
Sustainability Gap
USA
Norway
Daily Miles TraveledFor every man, woman and child
Working on Detroit