Density and Transit
Studying relationships




Portland has one of the nations best public transit systems.

It also continues to densify as it grows and pushes against it's Urban Growth Boundary. One challenge of that growth is knowing which areas may benefit most from the increased density.

Sites where transit access is abundant are naturally suited to growing denser, and many already have, but some may have been overlooked. These sites present an opportunity for higher density residential development. This study investigates if there are sites in Portland where transit is plentiful but housing density is still sparse.



Housing Density

First we want to look at the density of housing in Portland. The 2010 US Census gives us a measure that we can convert to dwelling units per acre. There is a huge variability here, and the map is scaled to highlight the lower end of it.

Housing Density (DU/Acre)
24.5+
21-24.5
17.5-21
14-17.5
10.5-14
7-10.5
3.5-7
0-3.5
Transit Access

Next we want to look at how accessible public transit is to each block. All of Portland's transit stops are mapped and their catchment area is projected over the blocks. The overlapping area is added up and divided by the size of the block to get a score, representing the amount of transit available a short distance from any point on the block. Again, very high variability led us to truncate the scale to better represent important differences.

Transit Access Score
28+
24-28
20-24
16-20
12-16
8-12
4-8
0-4
High transit access, but low density

Finally, the value we are most intersted in, degree of housing under-utilization. For this we simply take the transit access score and divide it by the housing density. This gives higher values to sites with great transit access but very low housing density. Many of these have obvious potential for higher utilization.

Blocks with high transit
but low housing density
42+
36-42
30-36
24-30
18-24
12-18
6-12
0-6