HomeMy WebLinkAboutNB 1 CONV LEFT TURNS 12-15-86 NEW BUSINESS
DATE' DECENBER 2, 1986
TO:
WILLIAM HUSTON, CITY MANAGER
FROM:
PUBLIC WORKS DEPARTMENT/ENGINEERING DIVISION
SUBJECT: CONVERSION OF PERMISSIVE LEFT TURNS TO PROTECTED LEFT TURNS
,. J
RECOMMENDATION:
For the City Council meeting of December 15, 1986.
It is recommended that fourteen intersections utilizing permissive left turn
phasing be modified to full protected left turns and that a supplemental budget
appropriation in the amount of $20,000 in general fund monies be authorized.
BACKGROUND:
Given the expressed concern over the use of "permissive" left turn signals in the
City, staff was directed to identify those locations where such left turn controls
were in place. Staff was also requested to determine the cost of modifying the
permissive left turns to "protected" left turns.
It is noted that permissive left turns operate from the volume of traffic using
the left turn pocket. Typically a four car demand must be generated from the left
turn pocket before the green arrow will light. If the demand in the pocket is not
present, then only the green ball will light wherein drivers turn accordingly to
the availability of gaps in opposing traffic (hence the "permissive" left turn}.
Under the protected type of operation, the green arrow lights even if only one car
is in the pocket.
DISCUSSION:
There are fourteen intersections that in one direction or another (i.e. either
just the east/west direction or just north/south), operate via permissive left
turns and are presented in the following table:
Signals Operatin9 Under Permissive Left Turns
1. Irvine Boulevard at:
3. McFadden Avenue at:
a. Yorba a. Pasadena
b. Prospect b. Williams
c. Holt c. Tustin Village Way
d. Ritchey
2. Newport Avenue at:
4. Red Hill Avenue at:
a. Holt a. Irvine
b. Bryan b. Walnut
c Main c. Sycamore
' d. Carnegie
DECEMBER 2, 1986
PAGE TWO
If all these locations were converted to protected left turns, it would involve
such items as new mast arm signal heads as well as wiring and signing. The cost
would average about $2,200 per intersection or roughly $31,000 to convert all
locations using permissive left turns. However, because "permissive" left turns
imply that traffic volumes are indeed low enough where full turning protection is
unnecessary all the time, it may not be necessary to convert all locations.
Therefore, traffic counts and new left turn evaluations will be completed prior to
converting all locations.
The proposed modifications would include a green arrow only for left turn
movements with no left turn movements on the green ball. The modification of the
intersections of Newport Avenue at Irvine Boulevard, First Street, and E1 Camino
Real are included within a Hazard Elimination Safety (H.E.S.) project currently
under design and will be funded with 90% federal funds and 10% local funds which
have already been budgeted.
It is proposed to fund the $31,000 estimate as follows:
$20,000 - General funds
$11,000 - Redevelopment Agency funds
Reference is made to a second report under the Redevelopment Agency agenda for
authorization of the $11,000 expenditure.
6~ob Led~ndecke r
Director of Public Works/City Engineer
BL:JLC:jm
, J