CTPS
CENTRAL TRANSPORTATION PLANNING STAFF
Staff to the Boston Region Metropolitan Planning Organization
DRAFT MEMORANDUM
To:
Steve McLaughlin, MassDOT
From:
Ying Bao, Scott Peterson
Re:
Environmental Justice Analysis for Casey Overpass Project
December 20, 2011
This memorandum provides an overview of the environmental justice (EJ) analysis for the Casey
Overpass study. It includes a brief description of the methodology of the environmental justice
analysis utilized by CTPS. The impacts of each build alternatives (which will replace the existing
Casey Overpass) to the environmental justice population zones near Forest Hills are summarized.
A statistical analysis is performed to determine whether the impacts to the environmental justice
(EJ) areas are statistically significant as compared to the impacts to the non-environmental
justice (non-EJ) areas in terms of accessibility, mobility, and air quality.
BACKGROUND
Environmental justice is based on the principle that all people have a right to be protected from
environmental pollution and to live in and enjoy a clean and healthful environment. It is the
equal protection and meaningful involvement of all people with respect to the development,
implementation, and enforcement of environmental laws, regulations, policies, and the equitable
distribution of environmental benefits. The EJ policy will direct state resources to serve (but not
limited to) the high minority population and low-income neighborhoods across the state. These
resources will ensure that EJ populations have a strong voice in environmental decision making,
receive the full protection afforded them through existing environmental rules and regulations,
and increase access to investments that will enhance equality of life in these communities by
restoring degraded natural resources, enhancing open space and building the urban park network.
The environmental justice assessment is a detailed, system-level analysis, conducted by the
Boston Metropolitan Planning Organization (MPO) as part of the transportation equity program.
This assessment examines the distribution of benefits and burdens brought by the proposed
transportation system among EJ and non-EJ areas and among EJ and non-EJ population zones in
MPO region.
METHODOLOGY
This section will describe the definition of an environmental justice area and introduce the
performance measures adopted for the environmental justice analysis.
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
Steve McLaughlin, MassDOT
2
December 20, 2011
EJ Area Definition
CTPS developed a standard modeling routine to perform the environmental justice analysis. In
this analysis, EJ areas are geographic regions determined by the demographics of the populations
living in a transportation analysis zone (TAZ). The population characteristics used in the Boston
MPO’s regional equity program are as follows:
•
Low-income population – 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).
•
Minority population – 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.
Based on the above rules, 962 TAZs in CTPS model region were categorized as an EJ population
TAZ. Among them, 726 TAZs met the criteria of low-income population and 709 TAZs met the
criteria of minority population. The environmental justice TAZs in the urban core for this study
are shown in Figure 1 in the end of this memorandum.
It should be noted that both build alternatives to replace the existing Casey Overpass (“At
Grade” and “Bridge”) were modeled using 2035 demographic projections. The 2035
demographic forecasts assumed the characteristics of the residential populations in the project
area would remain the same as they were observed in 2000 US Census.
Performance Measures
Three categories of performance measures were adopted in the environmental justice analysis for
the Casey Overpass study. These performance measures work as indicators of benefits and
burdens for EJ and non-EJ TAZs. It should be noted that the typical EJ analysis which focuses on
transit populations whereas the EJ analysis for Casey Overpass study paid more attention to auto
trips travelling from and to the environmental justice TAZs. The three categories of performance
measures are:
•
•
•
Accessibility to jobs and needed services
Mobility and congestion
Environmental impacts
In term of travel, accessibility is determined by both the ability to reach desired destinations and
the ease of doing so. An accessibility analysis for an EJ study investigates the number of
employment opportunities, health care facilities, and higher education facilities, which can be
reached within 20 minutes by car. It also examines the average travel time from environmental
justice areas to industrial, retail, and service employment opportunities, health care, and higher
education institutions.
Steve McLaughlin, MassDOT
3
December 20, 2011
The mobility and congestion analysis focuses on the average door-to-door travel time under a
congested condition for auto trips travelling from and to the EJ areas. Two types of door-to-door
travel times examined are:
•
•
Highway production time – The average travel time of all auto trips departing from a
TAZ
Highway attraction time – The average travel time of all auto trips arriving at a TAZ
The environmental impact focuses on the impacts of the roadway or transit projects to the
regional and local air quality. The air quality analysis for EJ studies examines the volumes of
carbon monoxide (CO) and fine particulate matters (PM 2.5 ) emitted per square mile, and average
vehicle-miles traveled under the congested traffic conditions.
In order to evaluate the magnitude of benefits and burdens brought by the roadway projects to
accessibility, mobility and air quality of EJ and non-EJ neighborhoods, CTPS introduced t-test
analysis to determine whether the difference are statistically significant. Two-sample t-tests of
each performance measure were conducted between the samples of EJ and non-EJ TAZs in the
Casey Overpass study area. A t-test can examine whether or not the difference between the
means of two groups is significant. In statistical significance testing, the p-value is the
probability of obtaining a test statistic at least as extreme as the one that was actually observed,
assuming that the null hypothesis is true. When the null hypothesis is rejected, the result is said
to be statistically significant. In this study, the base hypothesis is that there is no significant
difference of the benefits and burdens between EJ and non-EJ TAZs. The significant level is
0.05. If the p-value is greater than or equal to 0.05, the difference of benefits or burdens brought
by the roadway alternative between EJ and non-EJ neighborhoods is statistically insignificant.
On the other hand, if the p-value is less than 0.05, the benefits or burdens will be considered
statistically significant.
RESULTS SUMMARY
Eight neighborhoods were selected in the vicinity of Forest Hills for the Casey Overpass study:
Hyde Park, Jamaica Plain, Mattapan, north Dorchester, Roslindale, Roxbury, South Dorchester,
and West Roxbury. 227 zones in the studied neighborhoods belong to EJ population zones, out
of which 27 are non-EJ population zones.
The differences were calculated between the build alternative and the existing conditions for
each TAZ. In the accessibility and mobility analyses, the benefits and burdens were averaged by
the number of residents in each zone. In the air quality analysis, they were weighted by the size
of zone. All results were aggregated to the study area for EJ and non-EJ TAZs, respectively.
Results focus on six-hour peak periods only.
Accessibility Analysis
Results from the accessibility analysis are summarized in table 1 and 2. Table 1 compares each
build alternative, the number of jobs and services available within 20 minutes by car, for EJ and
non-EJ neighborhoods, respectively. It also summarizes the average travel time from EJ and
Table 1 Accessibility Summary (Build Alternatives vs. Existing Conditions) – Employment Opportunities and Services
Basic Employment
Number of Available
Basic Jobs/Service
Retail Employment
Average Highway Time
(minute)
Number of Available
Retail Jobs/Service
Service Employment
Average Highway Time
(minute)
Number of Available
Service Jobs/Service
Average Highway Time
(minute)
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
Existing
57,300
45,850
15.7
15.4
60,350
50,350
14.9
14.6
387,900
274,850
15.6
14.8
At Grade
57,350
46,050
15.7
15.4
60,350
50,500
14.9
14.6
388,150
275,550
15.6
14.8
Bridge
57,150
45,850
15.7
15.4
60,200
50,350
14.9
14.6
387,550
274,800
15.6
14.8
Compare Build Alts to Existing Condition
At Grade vs. Existing
0.1%
0.4%
0.0%
0.0%
0.0%
0.3%
0.0%
0.0%
0.1%
0.3%
0.0%
0.0%
Bridge vs. Existing
-0.3%
0.0%
0.0%
0.0%
-0.2%
0.0%
0.0%
0.0%
-0.1%
0.0%
0.0%
0.0%
p-value in t-test (EJ vs. Non-EJ) *
At Grade
0.2126
0.4724
0.3620
0.4653
0.8021
0.1199
Bridge
0.7373
0.7124
0.9314
0.4023
0.7461
0.0941
Steve McLaughlin, MassDOT
5
December 20, 2011
non-EJ neighborhoods to reach these jobs and service. The results indicate that, compared to the
existing condition, there is no changes in travel time to destination jobs between both build
alternatives and the existing condition. In the “At-Grade” alternative, people in both EJ and nonEJ zones will be able to access more jobs within a 20 minute drive than the “Bridge” alternative
although it does show that the non-EJ zones have slightly more benefit than EJ zones. The
differences are negligible and t-tests indicate they are statistically insignificant.
Table 2 presents the number of health care facilities and higher education institutions that are
accessible within 20 minutes highway time, for both build alternatives. The results are also
compared to the existing condition. It shows in both alternatives, people in EJ zones can access
more hospitals and education institutions than in those from non-EJ zones. In the “At-Grade”
alternatives, people from EJ zones will be able to access more health care facilities than the
existing condition. Under both alternatives, people from EJ zones will lose some opportunities to
access education facilities within 20-minute drive. However, compared to the benefits/burdens
distributed to people from non-EJ zones, the difference is minimal and can be considered as
statistically insignificant.
The average travel time to access hospitals and education institutions remained almost the same
in both build alternatives as compared to the existing conditions for both EJ and non-EJ
populations.
Table 2 Accessibility Summary (Build Alternatives vs. Existing Conditions) - Colleges and
Health Care Facilities
Access to Education Facilities
Number of Available
College Enrollment
Access to Health Care
Average Highway Time
(minute)
Number of Available
Hospital Beds
Average Highway Time
(minute)
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
Existing
62,950
47,850
14.9
15.1
6,000
5,600
13.2
13.4
At Grade
62,750
48,800
14.9
15.1
6,050
5,600
13.3
13.4
Bridge
62,700
47,700
14.9
15.0
6,000
5,600
13.3
13.4
Compare Build Alts to Existing Condition
At Grade vs. Existing
-0.3%
2.0%
-0.1%
0.3%
0.8%
0.0%
0.2%
-0.3%
Bridge vs. Existing
-0.4%
-0.3%
-0.1%
-0.4%
0.0%
0.0%
0.2%
-0.3%
t-test (EJ vs. Non-EJ) *
At Grade
0.4212
0.7645
0.5655
0.0500
Bridge
0.9082
0.1038
0.2430
0.0948
In the meantime, figure 2 (in the end of this memorandum) presents the average travel times by
car in peak period for EJ and non-EJ population zones. Similar to the results in table 1 and 2, it
also shows that there is no significant change between the build alternatives and the existing
condition.
Steve McLaughlin, MassDOT
6
December 20, 2011
Mobility Analysis
Results from the mobility analysis are summarized in table 3 and figure 3 (below). In both the
existing condition and two build alternatives, the travel time for people traveling to and from the
EJ population zones are one to two minutes shorter than those of the non-EJ population zones. In
both build alternatives, the average production time is slightly longer than the existing condition,
especially for those departing from the non-EJ population zones in the “At-Grade” alternative.
However, these negatives affect the EJ population zones less than the non-EJ population zones.
Table 3 Mobility Summary (Build Alternatives vs. Existing Condition)
Average Highway Production
Time (minutes)
Average Highway
Attraction Time (minutes)
EJ
Non-EJ
EJ
Non-EJ
Existing
16.5
17.7
15.6
17.7
At Grade
16.5
17.9
15.5
17.7
Bridge
16.5
17.8
15.6
17.7
Compare Build Alts to Existing Condition
At Grade vs. Existing
0.2%
1.5%
-0.2%
0.0%
Bridge vs. Existing
0.4%
0.7%
0.0%
-0.1%
t-test (EJ vs. Non-EJ)*
At Grade
0.0029
0.2423
Bridge
0.2450
0.8658
Environmental Impact Analysis
The results of environmental impact analyses are shown in table 4 and figure 4. These analyses
focused on the impact to air quality with respect to congested roadway conditions. Overall, the
EJ population zones have more vehicle-miles traveled, CO emissions, and fine particle matter
pollution than non-EJ population zones in the existing condition and in both build alternatives.
However, there is insignificant change between the existing condition and build alternatives
among three measurements.
Steve McLaughlin, MassDOT
7
December 20, 2011
Table 4 Emission Impacts Summary (Build Alternatives vs. Existing Conditions)
VMT per Square Mile
CO per Square Mile (kg/mile2)
PM2.5 per Square Mile
(g/mile2)
EJ
Non-EJ
EJ
Non-EJ
EJ
Non-EJ
Existing
54,000
44,400
456
371
656
542
At Grade
54,100
44,400
456
371
656
542
Bridge
54,000
44,500
456
371
656
543
Compare Build Alts to Existing Condition
At Grade vs. Existing
0.2%
0.0%
0.0%
0.0%
0.0%
0.1%
Bridge vs. Existing
0.0%
0.2%
0.0%
0.0%
-0.1%
0.0%
t-test (EJ vs. Non-EJ)*
At Grade
0.5762
0.6007
0.5458
Bridge
0.8286
0.8928
0.8451
CONCLUSION
The environmental justice analysis indicates that both of the proposed alternatives (“At Grade”
or “Bridge”), in the year 2035 has minimal changes in the accessibility, mobility and
environmental impacts compared to the existing conditions for both environmental justicepopulation zones and non–environmental justice-population. Neither of the proposed alternatives
will benefit nor burden the EJ population TAZ’s more than the non-EJ TAZ’s.
SAP/yb/yb
Legend
MPO EJ Criteria:
Minority population and
low income
Minority population
Low income
CTPS
FIGURE 1
Environmental Justice Populations
Casey
Overpass
Study
CTPS
FIGURE 2
Compare the Accessibilities between EJ & non-EJ TAZ’s
Casey
Overpass
Study
CTPS
FIGURE 3
Compare the Mobility between EJ & non-EJ TAZ’s
Casey
Overpass
Study
CTPS
FIGURE 4
Compare the Environmental Impacts between EJ & non-EJ TAZ’s
Casey
Overpass
Study