0
Street Netw orks,
  Road Safety & Sustainability
             W  esley M arshall, P.E.
            Norm W Garrick, PhD
   ...
Ro ad S afe ty …
   in the Unite d S tate s
20


15


10

                                   Fatalities per million VMT
 5


 0
     192    193    194    195    196  ...
Fatalities: 8
VMT: 2 million miles
Fatalities per million VMT = 4

Population: 50,000
Fatalities per 100k pop. = 16

     ...
3,00
                                                                          24 x




                                  ...
Average VMT (per capita per day)
Road Safety in the U.S.


30                                                                          60,000




         ...
Road Fatalities per 100,000 Population by Country
      United States




                        (Source: Organisation fo...
International Road Safety




Why is the U.S. falling behind
the rest of the world when it
   comes to safety in the
   tr...
Road Safety

When it comes to trying
to make our roads safer…

                      The focus tends to be
               ...
California City Study

      24 medium-sized
      California cities

                 Cities selected to
                ...
CALIFORNIA CITY COMPARISON
                              Less Safe         Safer
                                Cities   ...
Why are these places
so different in terms of
   safety outcomes?
CALIFORNIA CITY COMPARISON
                     Less Safe             Safer
                       Cities              Cit...
Davis              Intersection   Vehicle Mode     % Fatal or
                     Density         Share       Severe Cras...
Me as uring S tre e t Ne two rks
How Do We Characterize Street Networks?
  Connected
          Dense      Link to Node Ratio
              Intersection Den...
Characterizing Street Networks

There are 3 fundamental items of interest
in characterizing a street network…


       i. ...
HIGH CONNECTIVITY ≠ A DENS E NETWORK
Intersection Density
     144            144            144

            Link to Node Ratio

     1.61           1.13     ...
S implifying S tre e t
     Patte rns
Neighborhood Micro Network           Citywide Macroscopic Network


                                                      ...
Carlsbad, California
NETWORK COMPARISON
                                           Tree
                      Linear                           ...
Cras h Data
Re s ults
STREET NETWORK COMPARISON
                           Safer          Less Safe
                                            ...
ROAD SAFETY COMPARISON
                           Safer        Less Safe
                                                 ...
SAFER CITIES – NETWORK DENSITY

 Network
  Density
Comparison

 1 Sq. Mile
 Grid Size                9x9             12x12...
S tatis tic al Analys is
Statistical Analysis
What do we want to know?



      How are street network
       measures associated
        (correlat...
Statistical Analysis
Built crash prediction models using
a generalized linear regression

Response Variables:

  Model 1: ...
Crash Model Results
                                                         Model 1         Model 2 Model 2 Model 3 Model...
FULL NETWORK CRASH MODELS                       Total Crashes   Severe Crashes   Total Fatal Crashes
                     ...
CITYWIDE MACRO CRASH MODELS                     Total Crashes   Severe Crashes   Total Fatal Crashes
                     ...
LT     TT     RT     GT



Intersection Density             90     140    130    160
Link to Node Ratio               1.09...
MODE CHOICE
                   LT       TT      RT     GT




% Walking          2.9%    3.5%    1.9%    2.9%
% Biking    ...
TT


MODE CHOICE MODEL                          Transit Mode          Pedestrian           Biking Mode           Automobil...
TG


 MODE
strian     CHOICE MODEL
            Biking Mode Automobile                    Transit Mode
                    ...
GG

  MODE CHOICE MODEL
strian  Biking Mode Automobile                        Transit Mode          Pedestrian           B...
VMT

                     LT   TT   RT   GT



VMT in Block Group
per capita per day   66   28   27   51




             ...
Effect on VMT?

                                                                   24 x




                              ...
Ro ad S afe ty & Mo de
               Cho ic e

       Gettingof which will requires
          All  things right help
    ...
Marshall - CNU Street Network Presentation
Marshall - CNU Street Network Presentation
Marshall - CNU Street Network Presentation
Marshall - CNU Street Network Presentation
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Transcript of "Marshall - CNU Street Network Presentation"

  1. 1. Street Netw orks, Road Safety & Sustainability W esley M arshall, P.E. Norm W Garrick, PhD an . Center for Transportation & Urban Planning University of Connecticut Sustainable Transportation Networks Congress for the NewUrbanism XVII June 13, 2009 Denver, Colorado
  2. 2. Ro ad S afe ty … in the Unite d S tate s
  3. 3. 20 15 10 Fatalities per million VMT 5 0 192 193 194 195 196 197 198 199 200 5 5 5 5 5 5 5 5 5
  4. 4. Fatalities: 8 VMT: 2 million miles Fatalities per million VMT = 4 Population: 50,000 Fatalities per 100k pop. = 16 Fatalities: 8 VMT: 1 million miles Fatalities per million VMT = 8 Population: 100,000 Population per 100k pop. = 8
  5. 5. 3,00 24 x ) 0 ns io i ll (b T VM 2,000 20 15 10 1,000 Fatalities per million VMT 5 Population 2.5 x 00 0 192 193 194 195 196 197 198 199 200 5 5 5 5 5 5 5 5 5
  6. 6. Average VMT (per capita per day)
  7. 7. Road Safety in the U.S. 30 60,000 ) ns Fatalities per 100,000 population io Total No. of Fatalities i ll 25 (b T VM 20 40,00 0 Fatalities per million VMT 15 10 20,00 0 5 Population 0 0 192 193 194 195 196 197 198 199 200 5 5 5 5 5 5 5 5 5
  8. 8. Road Fatalities per 100,000 Population by Country United States (Source: Organisation for Economic Co-operation and Development, OECD)
  9. 9. International Road Safety Why is the U.S. falling behind the rest of the world when it comes to safety in the transportation system? (Source: Organisation for Economic Co-operation and Development, OECD)
  10. 10. Road Safety When it comes to trying to make our roads safer… The focus tends to be on finding the most problematic locations http://imgs.sfgate.com/c/pictures/2007/01/03/ba_octavia28_009_rad.jpg and fixing them www.streetsblog.org
  11. 11. California City Study 24 medium-sized California cities Cities selected to represent a range of traffic safety levels Geographically diverse with locally generated traffic
  12. 12. CALIFORNIA CITY COMPARISON Less Safe Safer Cities Cities Population 59,845 65,719 (average) Road Fatalities 771 257 3.0 (total over 11 years) 5.8 sk = 1.9 e Ri per city per year Fatalities per Re lativ 100,000 pop. 9.8 3.3 (per year) Non-Highway Road Fatalities 676 200 3.4 (total over 11 years) sk = 1.5 e Ri per city per year 5.1 Non-HW Fatalities Re lativ per 100,000 pop. 8.6 2.5 (per year)
  13. 13. Why are these places so different in terms of safety outcomes?
  14. 14. CALIFORNIA CITY COMPARISON Less Safe Safer Cities Cities Population Density 2,673 per sq. mi. 5,736 per sq. mi. Mode Share Driving 95.8% 84.1% Walking 1.7% 5.4% Biking 0.7% 4.1% Transit 1.7% 6.6% Avg. Year of Incorporation 1932 1895
  15. 15. Davis Intersection Vehicle Mode % Fatal or Density Share Severe Crashes Pre 1940 211 / sq. mi 40.6% 1.6% 1940s 122 58.9% 3.9% 1950s 169 63.0% 2.6% 1960s 172 64.7% 2.3% 1970s 132 81.3% 3.0% 1980s+ 111 85.9% 3.0% 1940 1950 2000 1990 1980 1970 1960
  16. 16. Me as uring S tre e t Ne two rks
  17. 17. How Do We Characterize Street Networks? Connected Dense Link to Node Ratio Intersection Density Gridded Road Density Hierarchical Block Size Patterns
  18. 18. Characterizing Street Networks There are 3 fundamental items of interest in characterizing a street network… i. Street Connectivity ii. Street Network Density iii. Street Patterns
  19. 19. HIGH CONNECTIVITY ≠ A DENS E NETWORK
  20. 20. Intersection Density 144 144 144 Link to Node Ratio 1.61 1.13 1.16 HIGH CONNECTIVITY ≠ A DENS E NETWORK
  21. 21. S implifying S tre e t Patte rns
  22. 22. Neighborhood Micro Network Citywide Macroscopic Network Tree Linear Grid Tributary Radial Tree Grid Adapted from Stephen Marshall, Streets & Patterns
  23. 23. Carlsbad, California
  24. 24. NETWORK COMPARISON Tree Linear Grid Tributary Radial Tree Avg. Year of Development 1966 1965 1974 1966 Grid Avg. Year of Development 1950 Pre 1940 Pre 1940
  25. 25. Cras h Data
  26. 26. Re s ults
  27. 27. STREET NETWORK COMPARISON Safer Less Safe Difference Cities Cities Intersection 106 per sq. mi. 63 per sq. mi. -40.6% Density Dead End 32 per sq. mi. 23 per sq mi. -28.1% Density % Dead Ends 23.2% 26.7% Macro 7.5 per sq. mi. 4.9 per sq. mi. -34.7% Node Density % Major Nodes 7.1% 7.8% Connectivity Measures Link to Node Ratio 1.34 1.29 -3.7% Connected Node Ratio 0.76 0.73 -4.0%
  28. 28. ROAD SAFETY COMPARISON Safer Less Safe Difference Cities Cities Fatal Crashes 3.3 per year 9.8 per year 197.0% per 100,000 pop. Severe Crashes 16.4 per year 18.4 per year 12.2% per 100,000 pop. Severity Risk 1.9% 68.4% (% Fatal or Severe) 3.2% Macro Road Fatal or Severe per 100k pop. 16.4 per year 17.4 per year 6.1% Severity Risk (% Fatal or Severe) 1.9% 3.2% 68.4% Micro Road Fatal or Severe per 100k pop. 2.7 per year 4.6 per year 70.4% Severity Risk (% Fatal or Severe) 1.5% 3.1% 58.8%
  29. 29. SAFER CITIES – NETWORK DENSITY Network Density Comparison 1 Sq. Mile Grid Size 9x9 12x12 15x15 Block Length 660’ 480’ 375’ Intersection Density 81 144 225 < 81 81-144 144-225 225+ Risk of Injury 41.0% 38.5% 39.1% 37.7% (non-highway) Risk of Severe Inj. 3.3% 1.9% 1.8% 1.5% (non-highway) Risk of Fatality 0.5% 0.3% 0.2% 0.2% (non-highway)
  30. 30. S tatis tic al Analys is
  31. 31. Statistical Analysis What do we want to know? How are street network measures associated (correlated) with road safety outcomes?
  32. 32. Statistical Analysis Built crash prediction models using a generalized linear regression Response Variables: Model 1: Total No. of Crashes Model 2: Total No. of Severe Injury Crashes Model 3: Total No. of Fatal Crashes
  33. 33. Crash Model Results Model 1 Model 2 Model 2 Model 3 Model 3 Model 4 Model 1 Severe Injury Severe Any Injury Fatal & Fatal Crashes Total Crashes Crashes Total Crashes Fatal Crashes Variables Variables Crashes Injury Crashes Street NetworkNetwork Measures Street Street Pattern Pattern Type (categorical) Street Type (categorical) Intersection Density Intersection Density Macro-Intermediate Intersection Density Macro-Intermediate Intersection Density Dead End Node Density Dead End Node Density Link to Node Ratio Link to Node Ratio Curvilinear (0, 1) Macro Road Characteristics Street Level Data Avg. # of Lanes Avg. # of Lanes Avg. Width of Outside Shoulder Avg. Width of Outside Shoulder Raised Median Median (0, 1) Raised (0, 1) Painted Painted Median (0, 1) Median (0, 1) % of Macro Road Length Length with On-Street Parking % of Macro Road with On-Street Parking % of Macro Road Length Length with Bike Lanes % of Macro Road with Bike Lanes % of Macro Road Length Length with Curbs % of Macro Road with Curbs Exposure Exposure VMT VMT Proxy for Activity Proxy for Activity Miscellaneous Miscellaneous Distance from City Center Distance from City Center Avg. Income Avg. Income Adjacent Limited Access Highway Mixed Land Uses = Significant with Positive Association (More Crashes) = Significant with Negative Association (Fewer Crashes) = Not Significant
  34. 34. FULL NETWORK CRASH MODELS Total Crashes Severe Crashes Total Fatal Crashes (Model 1) (Model 2) (Model 3) % Change % Change % Change Intersection Density 81 14.15% 20.05% 53.75% 144 (reference value) - - - 225 -15.64% -20.94% -42.48% 324 -31.48% -40.67% -70.74% Link to Node Ratio 1.1 -14.29% -12.20% -28.21% 1.25 (reference value) - - - 1.4 16.67% 13.90% 39.29% 1.55 36.13% 29.73% 94.02% Total No. of Lanes on Macro Roads 2 (reference value) - - - 4 65.17% 33.96% 34.15% 6 172.81% 79.46% 79.95% Distance from City Center (miles) 0 41.48% 23.71% -12.86% 1 18.95% 11.23% -6.65% 2 (reference value) - - - 3 -15.93% -10.09% 7.12% 4 -29.32% -19.17% 14.75% % of Macro Road Length with On-Street Parking 0% (reference value) - - - 50% 18.26% 19.49% - 100% 39.86% 42.79% - % of Macro Road Length with Bike Lanes 0% (reference value) - - - 50% - - -14.29% 100% - - -26.53%
  35. 35. CITYWIDE MACRO CRASH MODELS Total Crashes Severe Crashes Total Fatal Crashes (Model 4) (Model 5) (Model 6) % Change % Change % Change Intersection Density 81 7.85% 13.43% 39.52% 144 (reference value) - - - 225 -9.26% -14.96% -34.83% 324 -19.43% -30.23% -61.38% Link to Node Ratio 1.1 - - -24.30% 1.25 (reference value) - - - 1.4 - - 32.10% 1.55 - - 74.50% Total No. of Lanes on Macro Roads 2 -45.82% -30.54% -23.08% 4 (reference value) - - - 6 84.56% 43.96% 30.01% Distance from City Center (miles) 0 51.26% 35.28% -12.88% 1 22.99% 16.31% -6.66% 2 (reference value) - - - 3 -18.69% -14.02% 7.14% 4 -33.89% -26.08% 14.78% % of Macro Road Length with On-Street Parking 0% -18.12% -15.10% 19.93% 50% (reference value) - - - 100% 22.13% 17.78% -16.62% % of Macro Road Length with Bike Lanes 0% - - 20.42% 50% (reference value) - - -
  36. 36. LT TT RT GT Intersection Density 90 140 130 160 Link to Node Ratio 1.09 1.15 1.18 1.24 Expected Total Crashes 290 202 275 213 Expected Severe Injury Crashes 5.5 3.8 4.1 5.2 Expected Fatal Crashes 1.2 0.9 1.1 1.0 (Non-HW Crashes) LG TG RG GG Intersection Density - 225 289 265 Link to Node Ratio - 1.34 1.37 1.40 Expected Total Crashes - 191 211 209 Expected Severe Injury Crashes - 3.1 3.3 3.1 Expected Fatal Crashes - 0.8 0.6 0.7
  37. 37. MODE CHOICE LT TT RT GT % Walking 2.9% 3.5% 1.9% 2.9% % Biking 1.6% 2.5% 0.9% 1.7% % Public Transit 3.3% 4.3% 2.1% 2.9% % Driving 92.2% 89.7% 95.1% 92.5% LG TG RG GG % Walking N/A 4.8% 4.0% 9.5% % Biking N/A 3.3% 4.2% 4.6% % Public Transit N/A 4.3% 10.2% 10.9% % Driving N/A 87.6% 81.6% 75.0%
  38. 38. TT MODE CHOICE MODEL Transit Mode Pedestrian Biking Mode Automobile Share Mode Share Share Mode Share (all other variables (all other variables (all other variables (all other variables held at mean) held at mean) held at mean) held at mean) Variables BASELINE BY STREET PATTERN TYPE 3.66% 2.28% 1.71% 92.35% Intersection Density 81 3.81% 1.94% 1.29% 92.96% 144 3.65% 2.30% 1.74% 92.31% 225 3.44% 2.85% 2.56% 91.15% 324 3.18% 3.69% 4.06% 89.07% Link to Node Ratio 1.1 3.42% 2.40% 1.74% 92.44% 1.25 4.17% 2.05% 1.65% 92.13% 1.4 5.06% 1.75% 1.55% 91.63% 1.55 6.14% 1.50% 1.46% 90.91% Total No. of Lanes on Macro Roads 2 4.48% 2.34% 1.72% 91.46% 4 2.80% 2.19% 1.68% 93.32% 6 1.74% 2.05% 1.63% 94.58% Distance from City Center (miles) 0 3.30% 4.03% 3.18% 89.49% 1 3.48% 3.06% 2.36% 91.11% 2 3.65% 2.31% 1.74% 92.30% 3 3.82% 1.74% 1.27% 93.17% 4 3.98% 1.31% 0.93% 93.78%
  39. 39. TG MODE strian CHOICE MODEL Biking Mode Automobile Transit Mode Transit Mode Pedestrian Pedestrian Biking Mode Biking Mode Automobile Automobile Share Share Mode Share Share Share Mode Share Mode Share Share Share Mode Share Mode Share variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) Variables 28% BASELINE BY STREET PATTERN 92.35% 1.71% TYPE 3.66% 4.18% 2.28% 3.93% 1.71% 3.39% 92.35% 88.51% Intersection Density 94% 81 1.29% 92.96% 3.81% 5.94% 1.94% 4.69% 1.29% 2.72% 92.96% 86.64% 30% 1441.74% 92.31% 3.65% 5.10% 2.30% 4.35% 1.74% 3.00% 92.31% 87.55% 85% 2252.56% 91.15% 3.44% 4.19% 2.85% 3.93% 2.56% 3.38% 91.15% 88.50% 69% 3244.06% 89.07% 3.18% 3.27% 3.69% 3.47% 4.06% 3.91% 89.07% 89.35% Link to Node Ratio 40% 1.11.74% 92.44% 3.42% 2.58% 2.40% 2.87% 1.74% 1.59% 92.44% 92.95% 05% 1.65% 1.25 92.13% 4.17% 3.49% 2.05% 3.50% 1.65% 2.55% 92.13% 90.46% 75% 1.41.55% 91.63% 5.06% 4.67% 1.75% 4.22% 1.55% 4.05% 91.63% 87.06% 50% 1.46% 1.55 90.91% 6.14% 6.16% 1.50% 5.01% 1.46% 6.32% 90.91% 82.52% Total No. of Lanes on Macro Roads 34% 2 1.72% 91.46% 4.48% 7.15% 2.34% 6.38% 1.72% 3.80% 91.46% 82.66% 19% 4 1.68% 93.32% 2.80% 2.10% 2.19% 2.10% 1.68% 2.85% 93.32% 92.95% 05% 6 1.63% 94.58% 1.74% 0.57% 2.05% 0.64% 1.63% 1.97% 94.58% 96.82% Distance from City Center (miles) 03% 0 3.18% 89.49% 3.30% 3.88% 4.03% 5.47% 3.18% 4.86% 89.49% 85.79% 06% 1 2.36% 91.11% 3.48% 4.12% 3.06% 4.19% 2.36% 3.63% 91.11% 88.06% 31% 2 1.74% 92.30% 3.65% 4.35% 2.31% 3.18% 1.74% 2.69% 92.30% 89.77% 74% 3 1.27% 93.17% 3.82% 4.57% 1.74% 2.41% 1.27% 1.99% 93.17% 91.04% 31% 4 0.93% 93.78% 3.98% 4.78% 1.31% 1.81% 0.93% 1.46% 93.78% 91.95%
  40. 40. GG MODE CHOICE MODEL strian Biking Mode Automobile Transit Mode Pedestrian Biking Mode Automobile Share Share Mode Share Share Mode Share Share Mode Share variables (all other variables (all other variables (all other variables (all other variables (all other variables (all other variables mean) held at mean) held at mean) held at mean) held at mean) held at mean) held at mean) Variables 3% BASELINE BY STREET PATTERN88.51% 3.39% TYPE 9.00% 3.66% 8.79% 2.28% 4.09% 1.71% 78.13% 92.35% Intersection Density 9% 812.72% 86.64% 8.93% 3.81% 5.08% 1.94% 2.84% 1.29% 83.15% 92.96% 5% 3.00% 144 87.55% 8.98% 3.65% 6.14% 2.30% 3.23% 1.74% 81.65% 92.31% 3% 3.38% 225 88.50% 9.01% 3.44% 7.81% 2.85% 3.79% 2.56% 79.39% 91.15% 7% 3.91% 324 89.35% 8.96% 3.18% 10.40% 3.69% 4.56% 4.06% 76.08% 89.07% Link to Node Ratio 7% 1.59% 1.1 92.95% 8.40% 3.42% 9.93% 2.40% 3.21% 1.74% 78.47% 92.44% 0% 2.55% 1.25 90.46% 8.69% 4.17% 9.35% 2.05% 3.62% 1.65% 78.34% 92.13% 2% 4.05% 1.4 87.06% 8.99% 5.06% 8.80% 1.75% 4.08% 1.55% 78.13% 91.63% 1% 6.32% 1.55 82.52% 9.29% 6.14% 8.28% 1.50% 4.59% 1.46% 77.85% 90.91% Total No. of Lanes on Macro Roads 8% 2 3.80% 82.66% 8.28% 4.48% 8.57% 2.34% 3.45% 1.72% 79.70% 91.46% 0% 4 2.85% 92.95% 10.16% 2.80% 9.09% 2.19% 5.27% 1.68% 75.48% 93.32% 4% 6 1.97% 96.82% 12.26% 1.74% 9.48% 2.05% 7.93% 1.63% 70.33% 94.58% Distance from City Center (miles) 7% 0 4.86% 85.79% 8.39% 3.30% 11.10% 4.03% 5.28% 3.18% 75.23% 89.49% 9% 1 3.63% 88.06% 9.04% 3.48% 8.62% 3.06% 4.00% 2.36% 78.33% 91.11% 8% 2 2.69% 89.77% 9.65% 3.65% 6.62% 2.31% 3.00% 1.74% 80.72% 92.30% 1% 3 1.99% 91.04% 10.22% 3.82% 5.05% 1.74% 2.23% 1.27% 82.50% 93.17% 1% 4 1.46% 91.95% 10.75% 3.98% 3.82% 1.31% 1.65% 0.93% 83.78% 93.78%
  41. 41. VMT LT TT RT GT VMT in Block Group per capita per day 66 28 27 51 LG TG RG GG VMT in Block Group per capita per day - 21 23 24
  42. 42. Effect on VMT? 24 x ) ns io i ll (b T VM 8 x Population 2.5 x 192 193 194 195 196 197 198 199 200 5 5 5 5 5 5 5 5 5
  43. 43. Ro ad S afe ty & Mo de Cho ic e Gettingof which will requires All things right help a more comprehensive Redefining the Problem inform our efforts toward creating: approach that considers: Street Network Density & S afe r Street Design reStreet Connectivity Mo Co S us tainable s ig n e s mmunity De Plac Alternative Modes Street Patterns
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