Staff to the Boston Region Metropolitan Planning Organization
John Romano and Steve McLaughlin, MassDOT
December 15, 2011
Ying Bao, Scott Peterson
Summary of the Environmental Justice and Air Quality Analyses
Conducted for the Casey Overpass Project
The purpose of this memorandum is to provide an overview of the environmental justice and the
air quality analyses the Central Transportation Planning Staff (CTPS) conducted for the Casey
Overpass study. CTPS maintains a suite of modeling packages, which have been used in
numerous transportation studies, to examine transportation flows by mode, regional air quality
analysis, and environmental justice mobility and accessibility issues. The goal of these analyses
was to support MassDOT’s effort to submit an Environmental Notification Form (ENF). A
summary of the results of the environmental justice and air quality analysis are presented below.
The detailed analyses and results are presented in separate memoranda.
The environmental justice assessment is a detail-orientated, system-level analysis, conducted by
the Boston Metropolitan Planning Organization (MPO) as part of the transportation equity
program. This assessment examines the distribution of the transportation system’s benefits and
burdens among environmental justice (EJ) and non-environmental justice (non-EJ) areas and
among environmental justice and non-environmental justice population zones in MPO region.
The EJ analysis for the Casey Overpass project used the standard modeling procedure developed
by CTPS, with a focus on the study area for the year 2035. In this analysis, environmental justice
areas are geographic regions determined by the demographics of the people living in a
transportation analysis zone (TAZ), a unit of geography categorized by specific land use
activities. In this study, the definition of an environmental justice TAZ follows the criteria in the
Boston MPO’s regional equity program:
Low-income population TAZ – In 2000, the Boston MPO median household income was
approximately $55,800. A low-income population TAZ was defined as having a median
household income at or below 80 percent of this level ($44,640).
State Transportation Building • Ten Park Plaza, Suite 2150 • Boston, MA 02116-3968 • (617) 973-7100 • Fax (617) 973-8855 • TTY (617) 973-7089 • ctps@ctps.org
Minority population TAZ – 21.4 percent of the MPO population in 2000 was composed
of minorities (nonwhite and Hispanic). A minority population TAZ was defined as
having a percentage of minority population greater than 21.4 percent.
The environmental justice TAZs in the urban core for this study are shown in Figure 1 at the end
of this memorandum. The goal of this analysis is to determine if there are disparate impacts on
EJ populations due to the changes of the roadway network in the study area, using several
Three categories of performance measures were adopted in the environmental justice analysis for
Casey Overpass study. These performance measures work as indicators of benefits and burdens
for EJ and non-EJ TAZ’s. Since this project is not supposed to impact transit service in the area,
CTPS did not examine transit, but focused exclusively on several categories of highway
performance measures. The three categories of performance measures are: 1) Accessibility to
jobs and needed services, 2) Mobility and congestion, and 3) Environmental impacts.
The accessibility analysis investigated the number of employment opportunities, health care
facilities, and higher education facilities that could be reached within 20 minutes by car. It also
examined the average travel time from environmental justice areas to industrial, retail, and
service employment opportunities, health care, and higher education institutions. The mobility
and congestion analysis focused on the average door-to-door travel time and average vehiclemiles traveled under a congested condition for auto trips travelling to and from EJ areas. The
environmental impact analysis examined the volumes of carbon monoxide (CO) and fine
particulate matters (PM 2.5 ) emitted per square mile.
The results of the above analyses from the EJ areas near the study area were compared to those
from the non-environmental justice areas. Eight neighborhoods were selected in the vicinity of
Forest Hill for this study: Hyde Park, Jamaica Plain, Mattapan, north Dorchester, Roslindale,
Roxbury, South Dorchester, and West Roxbury. The results of the analysis indicated that
 Both of the proposed alternatives (“At Grade” or “Bridge”), in the year 2035 have
minimal changes on the accessibility, mobility and environmental impacts compared to
the existing conditions.
 Neither of the proposed alternatives adversely affected the EJ population TAZ’s more
than the non-EJ TAZ’s.
The air quality analysis utilized the same methodology used for regional air quality conformity
determinations, which was recently certified by the Federal Transit Administration and the
Federal Highway Administration for the Long Range Transportation Plan. The travel demand
model estimates traffic volumes, average highway speeds, vehicle-miles traveled and vehiclehours traveled and are used in conjunction with the emission rates developed by the
Environmental Protection Agency (EPA) MOBILE 6.2 emissions modeling software. CTPS
utilized these outputs to forecast emissions for the no-build condition, and the two build
alternatives in 2035.
The air quality analysis estimated emissions for carbon monoxide (CO), carbon dioxide (CO2),
nitrogen oxides (NOx), volatile organic compounds (VOCs), and particulate matters (PM 2.5 and
PM 10 ) from cars and trucks. Emissions from commuter rail diesel locomotives, transit service
boats, and MBTA buses and automobile emissions associated with park-and-ride lots were
estimated off model.
The Casey Overpass air quality analysis focused on the same neighborhoods described in the
environmental justice analysis. Since the emission factors and transit networks remained constant
between the no-build and build alternatives, any changes would only be the result of different
levels of roadway congestion and shifts in .
 The results of the regional air quality analysis showed that there were no significant
changes in the vehicle-miles traveled, vehicle-hours traveled, and average speed in the
selected neighborhoods near Forest Hills and the Jamaica Plain area. The changes of air
pollutions between the existing conditions and both build alternatives were minimal.
MPO EJ Criteria:
Minority population and
low income
Minority population
Low income
Environmental Justice Populations