a technical guide for conducting pedestrian safety assessments
a technical guide for conducting pedestrian safety assessments
a technical guide for conducting pedestrian safety assessments
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56 A TECHNICAL GUIDE FOR CONDUCTING PEDESTRIAN SAFETY ASSESSMENTS FOR CALIFORNIA CITIES<br />
APPENDIX D<br />
BLOCK RATIO INDEX<br />
BLOCK RATIO INDEX: MEASURING CONNECTIVITY<br />
Jennifer Dill (2004) presents the following measures of street connectivity:<br />
➜ Intersection density<br />
➜ Street density<br />
➜ Average block length<br />
➜ Link/node ratio<br />
➜ Connected node ratio = intersections/ (intersections + cul-de-sacs)<br />
➜ Alpha index = number of actual circuits/ maximum number of circuits<br />
Where a circuit is a finite, closed path starting and ending at a single node<br />
➜ Gamma index = number of links in the network/ maximum possible number of links between nodes<br />
➜ Effective walking area = number of parcels within a one-quarter mile walking distance of a point/ total number of<br />
parcels within a one-quarter mile radius of that point<br />
➜ Pedestrian route directness = route distance/ straight-line distance <strong>for</strong> two selected points<br />
Dill determined that the <strong>pedestrian</strong> route directness (PRD) measure is the best connectivity measure to reflect<br />
minimizing trip distances and route directness. However, it is difficult to use in research and policy. The PRD may be<br />
applied in practice by randomly selecting origin-destination pairs and calculating a sample <strong>for</strong> the subject area.
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