HomeMy WebLinkAbout07 PROTECTED/PERMISSIVE TRAFFIC SIGNAL REMOVAL 02-19-08AGENDA REPORT
MEETING DATE: FEBRUARY 19, 2008
TO: WILLIAM A. HUSTON, CITY MANAGER
FROM: PUBLIC WORKS DEPARTMENT/ENGINEERING DIVISION
SUBJECT: UPDATE ON THE CITY'S PROTECTED/PERMISSIVE LEFT TURN
TRAFFIC SIGNAL PHASING OPERATIONS
SUMMARY
As part of the City's on-going monitoring program related to protected/permissive left turn
(PPLT) traffic signal phasing operations, a comprehensive study has been prepared for the
nine existing intersection locations where PPLT traffic signal phasing operations are in effect.
Based upon the results of the study, it is recommended that the PPLT phasing operation be
retained at seven (7) intersections, and that at two (2) of the intersections the traffic signals
be converted to a protected left turn phasing operation.
RECOMMENDATION
It is recommended that the existing protected/permissive left turn traffic signal phasing
operations at the following seven (7) intersections be retained:
- EI Camino Real at Tustin Ranch Road
- EI Camino Real at Auto Center Drive
- EI Camino Real at Myford Road
- First Street at Pacific Street/Yorba Street
- Newport Avenue at Sixth Street/Walnut Street
- Walnut Avenue at Franklin Avenue
- Pioneer Road at Pioneer Way
It is also recommended that the existing protected/permissive left turn traffic signal phasing
operation be converted to a fully protected left turn phasing operation at the following two (2)
intersections:
- Red Hill Avenue at Walnut Avenue
- Newport Avenue at Walnut Avenue
FISCAL IMPACT
It is estimated that the cost to modify the traffic signals to a fully protected left turn phasing
operation at Red Hill Avenue /Walnut Avenue, and at Newport Avenue /Walnut Avenue is
$24,000. Sufficient funds to perform the work are available in the Engineering Division
Operating Account No. 01-402-6218.
Update on the City's Protected/Permissive Left Turn Traffic Signal Phasing Operations
February 19, 2008
Page 2
BACKGROUND
Protected/permissive left turn (PPLT) traffic signal phasing operation is a type of traffic signal
phasing which allows the flexibility of operating the traffic signal to provide both protected left
turn phasing (green arrow) and permissive left turn phasing (green ball). This operation
provides a left turn green arrow for a period of time at the beginning of the signal phase for a
direction of travel, then a yellow arrow, followed by a green ball indication. Left turns are
initially a protected movement with the green arrow, and then become permissive under the
green ball. That is, left turns must then yield to oncoming traffic, but may complete turns if
sufficient gaps exist. An advantage of PPLT is it provides more efficient movement of traffic
by allowing left turns on the green ball in addition to the green arrow. At the same time, this
can be a disadvantage because it introduces driver judgment in making a left turn on the
green ball, which can lead to driver error.
In 1999, left turn traffic signal phasing was converted to PPLT phasing at the following eight
(8) intersections based on City Council authorization:
- EI Camino Real at Tustin Ranch Road
- EI Camino Real at Auto Center Drive
- EI Camino Real at Myford Road
- First Street at Pacific Street/Yorba Street
- Newport Avenue at Sixth Street/Walnut Street
- Walnut Avenue at Franklin Avenue
- Red Hill Avenue at Walnut Avenue
- Newport Avenue at Walnut Avenue
In 2001 a new traffic signal was installed at Pioneer Road/Pioneer Way which incorporated
PPLT phasing operation.
DISCUSSION
As part of the City's on-going monitoring program related to PPLT traffic signal phasing
operations, a comprehensive study has been prepared for the nine existing intersection
locations where PPLT traffic signal phasing operations are in effect. The study is available
for review at the Public Works Department. Primary evaluation factors considered in the
study included the following:
- Left turn accident history;
- Number of opposing through lanes;
- Peak hour left turn traffic volumes;
- Peak hour opposing through traffic volumes;
- Unusual intersection geometrics;
- Sight distance restrictions; and
- Posted speed.
S:\City Council Items\2008 Council Items\Update on City's Protected-Permissive Left Turn Traffic Signal Operations.doc
Update on the City's Protected/Permissive Left Turn Traffic Signal Phasing Operations
February 19, 2008
Page 3
As a result of the study it is recommended that seven (7) of the nine (9) PPLT traffic signals
retain the PPLT left turn traffic signal phasing operations, and that the intersections of Red
Hill Avenue at Walnut Avenue and Newport Avenue at Walnut Avenue be converted from
PPLT traffic signal phasing operation to protected left turn phasing operation. Therefore, left
turns from Walnut Avenue onto Red Hill Avenue and from Newport Avenue onto Walnut
Avenue will only be allowed on a green arrow. The Tustin Police Department supports this
recommendation. As part of the signal modification at Red Hill Avenue/Walnut Avenue, the
westbound left turn lane from Walnut Avenue to southbound Red Hill Avenue would then be
restriped from a single left turn lane to double left turn lanes, thereby enhancing the overall
operation of the traffic signal. This could not have been done with the current PPLT traffic
signal phasing operation.
Tim D. Serlet
Director of Public Works/City Engineer
Dana R. Kasdan
Engineering Services Manager
Attachment: Map of Study intersections
S:\City Council Items\2008 Council Items\Update on City's Protected-Permissive Left Turn Traffic Signal Operations.doc
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Not to Scale
Katz, Okitsu & Associates Tustin F'~gure '1.2
Planning and Engineering Protected Permissive Left Turn Study Study Intersections