HomeMy WebLinkAboutOB 2 ST. JEANNE SCHOOL 05-15-89TO: WILLIAM HUSTON, CITY MANAGER
FROM: PUBLIC WORKS/ENGINEERING DIVISION
$~JECT: ST. JEANNE DE LESTONNAC SCHOOL
DRIVEWAY EVALUATION AND TRAFFIC SIGNAL STUDY
'71
RE COMMENDAT I ON:
At the pleasure of the City Council.
BACKGROUND:
'At a recent City Council ' meeting, staff was requested to evaluate
driveway conditions at Saint Jeanne's school. The school driveway
evaluation was to include the need for a signal, the influence of
traffic from Stoneglass Street (located slightly to the east of the
school driveway), and the sight distance available to drivers leaving
the school (and Stoneglass) with respect to the.55 Freeway overpass.
- DISCUSSION:
The typical speed of t~affic along Main Street .(near the school) was
measured via radar to be higher than 45 mph. From recent counts, the
total east/west volume on Main Street falls-just short of 16,000 cars. a
day. To evaluate the effect of.the speed and volume of Main Street
traffic, %ignal warrants were prepared to determine whether such a
device was necessary to enhance safety. As you know, the City of Tustin
relies on State Traffic Signal Warrants and their subsequent
satisfaction before concluding that a signal could be installed. In
this case, the applicable warrants reviewed were the Minimum Vehicular
Volume warrant, the Interruption of Continuous Traffic warrant, and two
other warrants that relate to specific peak hour traffic activity. The
evaluation also included the fact that the outbound movement from the
school occurs at the current Main Street driveway (one left turn lane
and one right turn lane) while the inbound movement occurs from a single
lane off Stoneglass.
In addition to individual analyses being performed at each of the above
(the outbound school driveway and also Stoneglass), we performed a
"joint" signal warrant analysis using the assumption that the existing
school driveway were closed. This would involve a slight modification
of on-site circulation with both the inbound and the outbound school
vehicular movements occurring at Stoneglass.
The results of the analyses revealed that neither the school driveway
volumes nor the Stoneglass traffic volumes could b_~ themselves warrant a
signal. In the case where the traffic from both locations was combined
(and both would, use Stoneglass), we found that the warrant for
Interruption of Continuous Traffic at least approaches the point of
ST. JEANNE DE LESTONNAC SCHOOL
DRIVEWAY-EVALUATION AND TRAFFIC SIGNAL STUDY
PAGE 2
being fully satisfied (seven of the required eight hours would be
satisfied). On the other hand, we f~und that full warrant satisfaction
would occur for those warrants that involve peak hour volumes (the peak
four hour volume warrant and the peak hour volume warrant).
Therefore, assuming that a full joint use agreement for Stoneglass could
be developed between the school and the Stoneglass residential area
(adjacent to the school entrance driveway), a signal could be installed
at Stoneglass and Main Street. Please note that a higher than normal
cost would be involved with this signal. As opposed to an $80-,000 (±)
cost for a typical "tee" intersection, the bridges on both sides of
Stoneglass will create unusual sight distance design requirements such
as advance warning beacons. This translates into an overall cost of
about $150,000. A signal at Stoneglass also assumes that the current
outbound movement from the school driveway would be eliminated and
directed to Stoneglass. As far as the associated modification to the
inbound movement is concerned, that could occur at the existing outbound
driveway (converted to inbound), at Stoneglass, or both. This would
~epend on the final design of the signal, a review of on-site school
circulation needs, and future Caltrans bridge/street improvement plans.
It was noted that a possibility exists that the current outbound school
driveway m%y evefltually have to be closed. From discussions with
Caltrans, future modifications to the I-5 overcrossing of Main Street
will include the lowering of Main Street in front of the school (about 3
feet). While they did not say that the driveway would assuredly have to
be closed, and indeed, they do not as yet have preliminary street or
bridge improvement plans, a lowering of Main Street by 3 feet would
create a difficult transition from the new street elevation to the
existing driveway. Therefore, unless more definitive information is
received, future signal plans at Stoneglass and the associated on-site
circulation changes should assume that all inbound movements would occur
at Stoneglass.
Bob Ledendecker
Director of Public Works/City Engineer
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~Consul'tlng Traffic Engineer