Rolling Out Measures of Non-Motorized Accessibility: What Can We Now Say? Kevin J. Krizek University of Colorado www.kevinjkrizek.org
Acknowledgements Mike Iacono Ahmed El-Geneidy Chen-Fu Liao
Outline I ) Why important? II) What measures of accessibility can offer? III) What we did (walking, cycling, transit) IV) What some measures show
Measurement / Evaluation Criteria: Focus on Urban Areas Performance measures (how are we doing?) Captures pressing needs Transportation (being one of them).don t we have such already?
TTI Congestion Index
Why Mobility Matters (to personal life and in the context of transportation planning) It provides: - potential for movement, - ability to get from one place to another - ability to move around Measures: - level-of-service - higher volume-to-capacity ratios Predominant Policy Solutions
Measurement / Evaluation Criteria: Focus on Urban Areas Performance measures (how are we doing?) Captures pressing needs Transportation & Land Use? Synergistically addresses: opportunities demand function behavior
Accessibility: Ease by which destinations can be reached j A im = O j f (C ijm ) A im = accessibility at i by mode m 1. O j = opportunities at j 2. C = measure of travel cost 3. ij m = measure of the ease or attractiveness of travel between i & j Knowing travel times Knowing behaviors
Accessibility opens additional policy prescriptions 1a. Build Infrastructure 1b. Enhance service &/or infrastructure 2a. Intensify land use 2b. Change land use
Source: League of American Bicyclists
Source: League of American Bicyclists
Source: League of American Bicyclists
Source: Don Shoup
Source: Don Shoup
Accessibility opens additional policy prescriptions 1a. Build Infrastructure 1b. Enhance service &/or infrastructure 2a. Intensify land use 2b. Change land use
1995 Jobs Schools Parks Shopping Automobile 2000Transit Jobs Schools Parks Shopping Automobile Bicycling Transit Walking 2005 Jobs Schools Parks Shopping Automobile Bicycling Transit Walking Bicycling Walking
Distance Decay: Walking 40% 30% Work Shopping Restaurant Entertainment Expon. (Work) Expon. (Entertainment) Expon. (Shopping) Expon. (Restaurant) Percent of Trips 20% 10% 0% 0 1 2 3 4 5 6 7 Distance (km)
Distance Decay: Bicycling 50% 40% 30% Work Shopping School Entertainment Trail Expon. (Work) Expon. (Shopping) Expon. (School) Expon. (Entertainment) Expon. (Trail) Percent of Trips 20% 10% 0% 0 5 10 15 20 25 30 35 40 45 Distance (km)
Impedance Functions Distance Time Work Walk y =.486e -1.683x y =.511e -.106x Bike y =.402e -.203x y =.146e -.040x Transit y =.667e -.093x y = e -.1*t_min Shopping W y =.469e -2.106x y =.368e -.094x B y =.343e -.514x y =.434e -.107x T y =.346e -.092x y = e -.1*t_min School W y = e -.1*t_dist y =.524e -.106x B y =.458e -.122x y =.424e -.100x T y =.406e -.116x y = e -.1*t_min Restaurant W y =.388e -1.397x y =.373e -.093x B y = e -.1*t_min T y = e -.1*t_min Recreation W y =.327e -.769x y =.556e -.100x B y =.367e -.375x y =.293e -.071x T y = e -.1*t_min
1995 Restaurant Accessibility by Bicycle
2000 Restaurant Accessibility by Bicycle
2005 Restaurant Accessibility by Bicycle
1995 Retail Accessibility by Walking
2000 Retail Accessibility by Walking
2005 Retail Accessibility by Walking
2000 Restaurant Accessibility by Bicycle 2000 Restaurant Accessibility by Bicycle
2005 Restaurant Accessibility by Bicycle
1995 Retail Accessibility by Transit (bw 4:00 4:15) 1995 Retail Accessibility by Transit
2000 Retail Accessibility by Transit (bw 4:00 4:15) 2000 Retail Accessibility by Transit
2005 Retail Accessibility by Transit (bw 4:00 4:15) 2005 Retail Accessibility by Transit
2000 retail opportunity
2005 retail opportunity
1995 Employment Accessibility by Transit 1995 employ transit
2000 Employment Accessibility by Transit 2000 employ transit
2005 Employment Accessibility by Transit 20055 employ transit
What we now can understand? Robust measures for measuring the performance of urban areas Measures can account for: Mode Destinations Demand Understand performance vis-à-vis array of policy prescriptions
Kevin J. Krizek University of Colorado www.kevinjkrizek.org
Employment (# of employees) Retail (overall annual sales of establishment) Restaurant (same) Public park access (sqm of park) Elementary (MCA test scores)
Questions How many block groups? What does the impedance function mean What is the significance of if/how/when they are measured differently? 6 am to 9pm (in 15 min increments) 60 intervals What was the bicycling cut off? What was the walking cut off? Transit restrictions?
Simplifying Dealing with 120 min bicycle cut off 5 mile walking cut off 1 transit transfer Using some decay functions
1995 Employment Accessibility by Transit (bw 4:00 4:15)
2000 Employment Accessibility by Transit (bw 4:00 4:15)
2005 Employment Accessibility by Transit (bw 4:00 4:15)
a L O T of D A T A Census blocks 42,240 of them Assumptions Transit frequency Cyclist distance Walking distance
Units are in minutes
What destinations? Mode Shopping Neighborhood retail Employment Recreatio n/ Parks Education -University -Primary Entertainme nt (includes bars) Gym/Heal th Club Airport Restaurant Walk Bicycle Transit Auto
Data Sources for Land use Database Metropolitan Council Land use Parcel points and polygons Dunn & Bradstreet Business locations and types (2005) Records for 135,928 Metro area businesses Detailed business data includes: Location Industry classification (NAICS and SICS) Sales Employees
General Destination Categories Shopping Food, Groceries, and Restaurants Fitness and Recreation Entertainment Education Health Care Parks Post Offices Financial Services Other Personal Services Professional Services Airports Transportation Other Based on North American Industrial Classification System codes and land use classification
Example of Specific Destinations Food, Groceries, and Restaurants Supermarkets and Grocery Stores (Retail, 5-digit) Convenience Stores (Retail, 5-digit) Warehouse Clubs and Supercenters (Retail, 5-digit) Specialty Food Stores (Retail, Manufacturing, 6-digit) Full-Service Restaurant (Accommodation & Food Service, 6-digit) Snack and Nonalcoholic Beverage Bars (i.e. coffee shops) (Accommodation & Food Service, 6-digit) Other Food Service (Accommodation & Food Service, 4-digit) Bars/Nightclubs (Accommodation & Food Service, 4-digit) (NAICS industries and level of disaggregation used in parenthesis)
Data Cleaning Fixed Records - Many misspellings & abbreviations - Assign street address to mall businesses Removed Records - 815 P.O. Boxes - 8,377 Not in 7-County Metro Area - 7,000 Bad / Missing Address Data (no zip code, street name, building number, etc.)
Understanding Measures of Accessibility they are: Relative to Mode specific Destination specific
Matching Summary
Detailed Land Use Data
but is Accessibility all about supply? NO! A hypothetical Ideally, accessibility measures should incorporate BOTH supply AND demand.
Estimating Decay Functions Fitting decay curves Modes: Auto, transit, bike, walk Purposes: Work, shopping, school, restaurant, recreation, trail access (bicycling)
Functional Form Types of decay functions Negative power: f(c) = c (-β) Negative exponential: f(c) = e (-βc) Combined: f(c) = c (α) e (-βc) We focus on the negative exponential function Definition of impedance Time vs. network distance
Flexible Forms
Impedance: Distance vs. Time Both have limitations as impedance measures Distance Cannot validate route choice, shortest path Difficult to validate speeds Time Duration data are self-reported, subject to perception error
Data Sources 4 Data sources used for analysis in Twin Cities: Met Council TBI HIS files Met Council transit on-board survey Hennepin County trail use survey Non-Motorized Pilot Project (NMPP) survey
Work Shopping School Distance Time Distance Time Distance Time Walk y =.486e -1.683x y =.511e -.106x y =.469e -2.106x y =.368e -.094x y =.524e -.106x Bike y =.402e -.203x y =.146e -.040x y =.343e -.514x y =.434e -.107x y =.458e -.122x y =.424e -.100x Transit y =.667e -.093x y =.346e -.092x y =.406e -.116x Drive Alone y =.504e -.088x y =.379e -.117x y =.371e -.122x Shared Ride y =.237e -.076x y =.381e -.130x y =.160e -.096x Notes: 1) For impedance functions where distance is the measure of separation, kilometers are the relevant units. Where time is the measure of separation, units are in minutes. 2) The dependent variable (y) measures the fraction of trips covering a given distance. 3) All grayed cells represent impedance functions that could not be estimated due to limited data. 4) Cells shaded blue can be calculated given available data, but have not been needed thus far. 5) Cells shaded red represent the recently acquired health care data. An impedance function can be calculated with these data, but the mode cannot be specified. Restaurant Recreation Trail Access Health Care Distance Time Distance Time Distance Time Distance Time y =.388e -1.397x y =.373e -.093x y =.327e -.769x y =.556e -.100x y =.367e -.375x y =.293e -.071x y =.119e -.333x y =.318e -.119x y =.426e -.140x y =.336e -.103x y =.333e -.093x
Impedance Functions e -0.1*dist_m e -0.1*t_min e -0.1*t_min e -0.1*t_min e -0.1*t_min e -0.1*t_min e -0.1*t_min
How we proceeded New networks GIS street layer; assumptions about speeds New zones Census block level Detailed land use/activity data Parcel-level land use merged with: Establishment level (D & B) business data Contains location, sales, employment, industrial classification
What s unique about measuring access for Transit, Walking, Cycling? Peculiarities: -Scale of analysis -Availability of data Balance: Useful measures w/ policy relevance Robust & reliable science
Accessibility: a HOT topic in policy circles has the potential to radically inform how we think about the structure of metropolitan areas loosely throw around terms and concepts without further refinement, however, run the risk of focusing on a topic w/o much meaning