Estimating Bicycling and Walking for Planning and Project Development: A Guidebook (2014) / Chapter Skim
Currently Skimming:
Pages 139-143
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 139... ...
139 Walk-Accessibility Accessibility is a general concept in travel modeling that typically refers to the ability of people to reach various destinations. It measures both the degree of development activity and the travel time needed to get to those activities.
|
From page 140... ...
140 Trip Attractions were determined through the following equations: Trip Distribution Trip productions and attractions are converted to origindestination trips through a "gravity model", which proportions the number of trips between zone i and zone j to the number of trips produced in zone i, the number of trips attracted to zone j, and inversely proportional to the impedance separating the two zones: ∑= ∗T P A F A F ij i j ij j ij j Where: Tij = trips from zone i to zone j Pi = trips produced in zone i Aj = trips attracted to zone j Fij = impedance function, i to j And: ∗ ∗F = a t eb gt Where: F = impedance t = perceived walk time, minutes a, b, g = calibrated coefficients e = base of natural logarithms (2.71828 .
|
From page 141... ...
141 Impedances The accessibility calculations that underlie the previously described demand model, and the path-finding that underlies the trip assignment model, all are based on travel times and impedances derived from the pedestrian network. Travel (walk)
|
From page 142... ...
142 A path set with minimum perturbation, used by such trip purposes as walking to work, is essentially the minimum path, and typically results in minor variations to jaywalk Default Sidewalk Types for Street Facility Types: Freeway None Arterial Marginal Collector High Local High Alleyway On-Street Other Marginal At intersection crosswalks and mid-block jay walks, basic crosswalk times are based on walking speed (specified separately and typically faster than sidewalk walk speed) , distance based on street width, and step-off conditions.
|
From page 143... ...
143 instead of using intersection crosswalks. A set with maximum perturbation, used by such trip purposes as leisure, will show a high level of variation and can typically result in going entirely around a block or finding another street to walk on.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.