the neighborhoods of tustin town center: a new ... - City of Tustin

A.3 Traffic and Circulation Testing
This report presents a preliminary traffic evaluation of potential new development in three
neighborhood study areas in the City of Tustin referred to as Center City, Southern Gateway and
West Village (see Figures 1 through 3). The traffic evaluation includes a preliminary qualitative
analysis of the implications of two land use alternatives (Alternatives A and B) with changes
in roadway circulation in select neighborhood areas and the potential impacts under existing
conditions. The three defined neighborhood areas are evaluated separately. It should be noted
that while there are two land use alternatives in each neighborhood area of the Tustin Town Center,
a number of combinations of alternatives both land use and circulation (i.e., Neighborhood Plan)
could actually be paired that would affect the final development plan.
ANALYSIS SCOPE
The land use and trip generation for each neighborhood area will first be summarized along
with information on any changes in circulation associated with the land use alternatives for each
neighborhood. Next, available existing count data (average daily traffic (ADT) volumes and
peak hour intersection capacity utilization (ICU) values) taken from various sources for the key
roadways and intersections evaluated will be presented. Lastly, the potential traffic impacts will
be discussed on the circulation system under existing conditions with potential hot spots/critical
locations identified that would require further and more detailed analysis at a later date.
Hot spot locations can be identified in three ways in this report. First, hot spot locations are those
locations that are likely impacted due to the project as defined by significance criteria and carried
out in a quantitative analysis. Second, in addition to a more detailed analysis at a later date that
would involve the use of the ICU methodology to determine project impact, certain areas will
require a special traffic operations analysis. Those areas are designated as “Traffic Operations
Hot Spots” and are locations where the standard ICU procedure does not fully depict the actual
traffic characteristics. It should be noted that the ICU method of calculating the volume-tocapacity
ratio of an intersection assumes isolated intersections and does not reflect any queuing
of vehicles that may occur between intersections of close proximity. An example of this close
proximity effect occurs on Newport Avenue and Red Hill Avenue at the I-5 interchange and the
adjacent intersections. Because of the closely spaced intersections, actual traffic conditions tend
to be somewhat congested during peak periods even though the ICU values indicate adequate
levels of service. Locations considered “hot spots” can also be sections of roadway where closely
spaced intersections or side friction caused by numerous driveways degrade the performance
of the roadway compared to its theoretical carrying capacity (referred to as Operations Hot
Spot). Third, “hot spots” can be intersections or sections of roadway that cannot be improved
to their full standard because of limited space due to right-of-way or other physical constraints
(referred to as Space Constrained Hot Spot). Space constrained hot spots can reach a V/C of
1.00 (rather than a threshold of .90) in recognition of the limitations involved in making physical
improvements.
In the future with a more detailed study, a set of performance criteria will be utilized to identify
future level of service deficiencies on the study area circulation system and also to define impacts
and peak hour ICU values of significance. Traffic LOS is designated “A” through “F” with LOS
“A” representing free flow conditions and LOS “F” representing severe traffic congestion. The
intersection criteria involve the use of peak hour ICU values. The ICU ranges that correspond to
LOS “A” through “F” are presented in Table 1. By practice, the ICU methodology assumes that
intersections are signalized. LOS “D” (ICU not to exceed .90) is the performance standard for the
intersections in the City of Tustin.
A-8 THE NEIGHBORHOODS OF TUSTIN TOWN CENTER
MARKET ANALYSIS AND NEIGHBORHOOD CONCEPT PLANS
STRATEGIC GUIDE 09.21.2010