Access to Quality Transit credit? Prove it!

By Adrian Charest, PE, LEED AP BD+C

RSMeans from The Gordian Group

Access to Quality Transit credit?  Prove it!

The intent behind USGBC’s Access to Quality Transit is to encourage development in areas that are connected by public transportation systems to reduce car usage…but do people want to live in areas that are highly connected to public transportation?  In other words, could the effect that multiple modes of transportation have on where people live be displayed?  Using a geographic information system and publicly available data, this article explores these questions and gets to, “Yes”.

The public transportation network in Boston is expansive and goes far beyond the city limits.  The system is comprised of four modes of transportation; subways, commuter rails, buses, and ferries, each with entry points consisting of stations, stops, or docks.  The systems operate independently from one another, but are complementary in that together they provide greater access to larger areas of the City.

The area around the entry points needs to be determined in order to develop answers to the posed questions.  Working with each system separately, a 1-mile buffer zone was created and merged together around each of the entry points for each respective system creating images as displayed in Figure 1 below.

Figure 1

                    Subway                                                                                                                  Commuter Rail  

                                                                          

Bus                                                                                                                             Ferry

Overlaying these buffers with the Year 2000 U.S. Census Data provides an understanding of each system’s influence on attracting people.  Using the buffers’ areas and the population captured by them enabled calculation of the population density around the entry points.  These results can be seen in Table 1 below which is ranked from greatest population density to least.

Table 1

Mode	Sq. Miles	Population	Pop / mi2
Subway	95	995,552	10,479
Commuter Rail	353	1,742,280	4,936
Bus	488	2,228,490	4,567
Ferry	75	261,307	3,484

However, what about the effects of multiple modes of transportation?  Overlaying the individual mode-buffers described above creates areas where there are 1-, 2-, 3-, and 4-modes of transportation available.  For instance, areas where there is only a subway or commuter rail station, a bus stop, or a ferry dock is ranked as 1-mode, not distinguishing between the mode types.  Areas where all four mode buffers overlapped are ranked as 4-mode, and any combination of 2 and 3 different mode types are ranked as 2- and 3-mode areas.  A graphic displaying the results of these combinations can be seen if Figure 2 below.

Figure 2

Overlaying these new buffers with the census data shows the impact that multiple modes of transportation have on where people want to live.  These outputs can be seen in Table 2 below where the influence can be clearly seen.; as the number of available modes increase, so does the number of people living in those areas.

Table 2

Area	Sq. Miles	Population	Pop / mi2
1 Mode	507	1,493,635	2,946
2 Mode	175	1,172,938	6,703
3 Mode	45	572,605	12,725
4 Mode	5	64,969	12,994

So what does this all mean?  That the Access to Quality Transit credit is in the right direction, people want to live in areas that are highly connected to public transportation systems.