visualizing job accessibility with

1
visualizing job accessibility with
GIS

• linthicum plan512 July 2006

2
who lives where?

• population available from 2000 Census tracts

3
who works where?

• job locations available by tract from 2000 CTPP

4
jobs/housing balance

• jobs to total population by Census tract

5
what does this data explain?

• job housing balance
• distribution
• density

what doesnt it explain?
consideration of costs (travel time) access to
jobs in other districts access to jobs by mode
6
what is job accessibility?

• accessibility number of opportunities within a
  certain distance or travel time(1)

Ai accessibility of zone I Oj opportunities
at zone j dij distance between zones ?
friction factor
A1
(1) Hanson, Susan. The Context of Urban Travel
Concepts and Recent Trends. Geography of Urban
Transportation, Third Edition, Susan Hanson and
Genevieve Giuliano, Editors. New York The
Guilford Press. 2004. pp 4-7
7
how to calculate ?

• the interaction formula
• becomes
• plot/regress ln(I) vs ln(d) to calculate the
  slope ?

All Modes ? -0.404
Auto ? -0.293
Non-Auto ? -0.251
8
job accessibility by all modes
All Modes ? -0.404
9
job accessibility by automobile
Auto ? -0.293
10
job accessibility by non-auto
Non-Auto ? -0.251
11
accessibility analysis shortcomings

• treats everyone in a tract as if they have the
  same mobility
• does not consider temporal variations such as
  peak / non-peak travel
• requires significant amounts of data
• does not distinguish between voluntary and
  necessary travel

12
questions?