| Department of Civil and Environmental Engineering
| Spring 1998 |
| CEE 129 Transportation Systems Analysis and Design |
Dr MG McNally |
Irvine PA12 Project: Task 5
In this final analysis phase, the focus will be the immediate area of
impact associated with the proposed development. Only three
arterials are included: Jeffrey Road from just north of I-405 to
north of Barranca Parkway; Sand Canyon from just north of I-405 to
north of Alton Parkway; and Alton Parkway from west of Jeffrey Road
to east of Sand Canyon. Only three current intersections are
included (noted as I in Figure 1). There are seven (7) gates, or
external stations (noted as G in Figure 1). All non-project area
zones are captured via these gates. There are only 5 internal zones
(numbered in Figure 1 - you may use any numbering scheme).
[Include figure]
The objective of this final project is to perform a Traffic Impact
Study of the defined area to ascertain traffic impacts of the proposed
development and to mitigate these impacts as necessary. Task 1
focuses on the development of a 1995 network and database using
Traffix, a transportation impact study tool. Proposed land use is
documented in Task 2. Mitigation requirements are discussed in Tasks
3 and 4.
REPORTING REQUIREMENTS
All stages of your analysis should be included in the Traffic
Impact Study. It is highly recommended that you follow report
guidelines in Chapter 10 of the ITE Report. Conventional course
report guidelines must be followed. All relevant Traffix reports
should be included, however, these may not substitute for your own
summary tables and figures. Your final report will address at least
the following tasks. Each member of your group must complete at least
one independent mitigation plans (identify the member with the plan)
TASK 1. Construct 1995 Base Network and Database
Using Traffix, construct a base network representing the above area.
All geometric data can be taken from your Project Phase I report for
PA12 and from the TransCAD model developed for the area in project
phases II-IV. To simplify the database, assume that all base volume
data as modeled by TransCAD accurately represents base traffic
conditions. After constructing the base network, additional
information is entered into Traffix under the Node menu. Consult
the Traffix manual for a Step-by-Step guide to building a dataset.
Code Alton Parkway as an Arterial.
TASK 2. Proposed Development
Table 1 summarizes proposed development for the 1999 horizon year.
Table 2a presents City of Irvine trip generation rates (AM and PM peak
rates and splits, as well as ADT on splits by trip purpose). Table 2b
provides similar information for land uses for which daily trip
generation is modeled via equation (the ratios provided factor daily
rates to peak hour rates). Note that these numbers are for person
trips and not vehicle trips; factors to convert to vehicle trips are
provided in Table 3 (it is suggested that you convert rates to vehicle
trips prior to entry into Traffix). Traffix allows you to input zone
(TAZ or centroid) names, multiple land use types, and period specific
trip rates (including in/out splits) under the
Zone/Generation menu.
Table 1. Proposed Development
| Zone | Cat | Land Use | Units |
|---|
| 1 | 101 | SF Detached | 480 DU | |
| 102 | Cluster A | 670 DU |
| 2 | 102 | Cluster A | 460 DU |
| 109 | Commercial | 150 TSF |
| 3 | 103 | Cluster B | 350 DU |
| 109 | Commercial | 20 TSF |
| 4 | 102 | Cluster A | 350 DU |
| 103 | Cluster B | 600 DU |
| 121 | Office | 300 TSF |
| 5 | 101 | SF Detached | 480 DU |
| 102 | Cluster A | 300 DU |
Table 2a. City of Irvine Person Trip Rates
| Cat |
Land Use | Units |
AM Peak | PM Peak |
ADT
Rate |
Productions | Attractions |
|---|
| In | Out | In | Out | HBW |
HBO | NHB | HBW | HBO | NHB |
|---|
| 101 | SF Detached |
DU | 0.26 | 0.67 |
0.85 | 0.48 | 12.83 | 0.18 | 0.41 |
0.13 | 0.0 | 0.15 | 0.13 |
| 102 | Cluster A |
DU | 0.18 | 0.63 |
0.73 | 0.33 | 10.84 | 0.17 | 0.51 |
0.10 | 0.0 | 0.12 | 0.10 |
| 103 | Cluster B |
DU | 0.13 | 0.53 |
0.55 | 0.28 | 8.82 | 0.16 | 0.59 |
0.08 | 0.0 | 0.09 | 0.08 |
Table 2b. City of Irvine Person Trip Rates (equation)
| Cat |
Land Use | Units |
A | B |
AM Peak | PM Peak |
Productions | Attractions |
|---|
| R1 | In/Out | R2 | In/Out | HBW |
HBO | NHB | HBW | HBO | NHB |
|---|
| 109 | Commercl | TSF | 0.625 |
6.376 | .039 | 52/48 | .072 |
49/51 | .0 | .0 | .23 |
.05 | .49 | .23 |
| 121 | Office | TSF | 0.756 | 3.887 |
.085 | 75/25 | .084 | 24/76 |
.0 | .0 | .31 | .29 | .09 | .31 |
Table 3. City of Irvine Person to Vehicle Trip Conversion
Factors
| Type | Trip purpose | Average Vehicle Occupancy |
|---|
| HBW | Home-based Work | 1.10 persons/vehicle |
| HBO | Home-based Other | 1.33 persons/vehicle |
| NHB | Non-home-based | 1.25 persons/vehicle |
TASK 3. Traffic Estimation and Impact Assessment
Traffix requires the input of anticipated trip distribution to the
identified network gates. You should estimate these percentages from
the initial TransCAD analysis completed in prior projects. This
information is entered under the Zone/Distribution menu.
Prior to inputing these percentages, you will need to identify paths
from all zones and all gates. In the base network, there will be only
one path for each zone/gate pair; in your future "mitigated" network,
you may have the opportunity to specify alternative routes (for which
specified percentages of traffic would utilize in accessing gates).
Evaluate base 1995 conditions (without project) and future 1999
conditions with the proposed development on the base network. Traffix
can evaluate intersection performance via a variety of methods (both
ICU 1 and HCM 85 or 95 should be used) for base conditions (based on
turning movements for the base year, then the incremental effect of
new development can be superimposed upon these base flows and the
resulting intersection performance assessed. Traffix can also
evaluate arterials (Alton is selected in this study). See
Step 8 in the Traffix manual for the process of
running an analysis (titles, reports, parameters, options, etc.).
You may also consult the on-line
guide for help and hints.
Carefully review the reporting capabilities of Traffix. Much of the
summary information associated with traffic impacts of proposed
development is automatically compiled by the program.
TASK 4. Traffic Mitigation and Impact Fee Allocation
Traffix simplifies the process of estimating the impact of basic
mitigation strategies. The choice of strategies. and the resultant
system design, is a function of the nature and magnitude of impact,
local requirements and design standards, and professional experience.
In this project, you should consider at leats the following general
approaches, independently or jointly:
Travel Demand Management, including trip reduction via carpooling,
transit, and alternative mode and work schedule policies. Check to
see what assumptions are acceptable for the local area for each of
these policies.
- Site Development Changes, including reducing the scale of
development, the mix of land uses (with internal capture
potential), and the type of land use (time-of-day
effects).
- Improving Existing Traffic Control, including signal timing (cycle
length, phasing, coordination, etc.) and other control
approaches.
- Traffic Engineering Improvements, including new traffic control
devices, geometric design changes (new or altered lanes,
restripped or added), new or moved access points.
- The easiest way to investigate alternative mitigation strategies
is to utilize the LOSMitig8 menu in Traffix. This
interactive screen allows the user to quickly test the impact of
different lane geometries and signal timing
configurations (see Step 10 in the Traffix
Manual). Traffix also incorporates two
approaches for impact fee assessment based on: (a) trip
generation and on (b) trips contributed to each intersection.
Use option (b). Be sure to fully summarize proposed
mitigation in the Recommendations section of
your Traffic Impact Study.
Assumptions
The following assumptions are made. Be sure to include a list of
these and all othre assumptions in your final report.
- Assume an annual 2 percent increase in all non-project traffic
for the four year period between the base year (1995) and the
planned openning of the project in 1999.
- Assume some reasonable policy for pass-by trips (including for
trips between zones).
- Assume specific infrastructure improvement, or Impact Fees, are
not known. Enter impact fees of 1.0 so that resultant
calculations show impacts in percentage terms.
- Assume City of Irvine standards for intersection and arterial
impact (see Project Phase IV).
Return to course home page
Last modified: Mon Jun 8 02:16:01 1998