HomeMy WebLinkAboutAgenda Statement 1983/08/16 Item 26 9' 1
COUNCIL AGENDA STATEMENT
Item 26
Meeting Date 8/16/83
ITEM TITLE: Report on Bonita Road/I-805 Traffic Study
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SUBMITTED BY: City Engineer t (4/5ths Vote: Yes No x )
REVIEWED BY: City Manager
In response to City Council , Safety Commission, and citizen requests, the
Traffic Engineering Division has completed a review of traffic conditions on
Bonita Road in proximity to the I-805 interchange. As a part of this review,
staff has met with representatives of CalTrans and the County to evaluate
traffic characteristics such as volumes, turn movements, and accident
history. Several short term improvement projects were identified that will
facilitate traffic flow. These will be implemented in the near future.
RECOMMENDATION: That Council accept this report.
BOARDS/COMMISSIONS RECOMMENDATION: Not applicable.
DISCUSSION:
Staff' s review of traffic conditions on Bonita Road in proximity to the I-805
interchange disclosed several factors which contribute to a lower level of
service on this segment of roadway. These are:
1 . high traffic volumes on Bonita Road (approximately 35,000 vehicles per
day) ,
2. high demand for left turning movements onto I-805 (both northbound and
southbound) ,
3. high demand for eastbound left and southbound right turns at Plaza Bonita
Road (traffic going to and from the Plaza Bonita Shopping Center) ,
4. lack of traffic signal interconnect between the Plaza Bonita signal
(County) and the freeway ramp signals (CalTrans) , and
5. the short spacing between existing traffic signals.
Safety factors include:
1 . the high demand for turning movements in this roadway segment,
2. the short weaving distance between the northbound 1-805 off ramp and Plaza
Bonita Road, and
3. the free right turn off ramps for I-805.
Page 2, Item 26
Meeting Date 8/16/83
In June, Traffic Engineering staff met with CalTrans and County
representatives, reviewed the traffic characterisitcs, problems and
constraints, and developed several short-term projects to mitigate most of the
above factors.
The following is a summary of those improvements, their anticipated impacts
and time schedule:
1 . The County agreed to change the controller for the signal to Plaza Bonita
Road to split the north and south legs into separate phases. This allows
for southbound to westbound double right turn lanes. (This has recently
been completed). Also, they will study the installation of a right turn
arrow for this move to overlap with the eastbound to northbound left turn
arrow, thus facilitating both heavy turning moves at the same time. (It
is noted that the latter would require the prohibition of "U"-turns at the
signal to prevent conflicts. ) These changes should provide more green
time and less delay for Bonita Road traffic.
2. The County will interconnect the signal at Plaza Bonita Road with the
State signals at the freeway ramps. They anticipate that this will be
done in the first quarter of FY 1983-84. The impact of this improvement
will be to mitigate the problems associated with short spacing between
signals and the high turning movements, thus an overall improvement in
traffic flow on Bonita Road.
3. CalTrans will redesign and reconstruct the freeway ramps to:
a. Eliminate the free right turn lanes for the off ramps,
b. provide signal controlled double right turn lanes for the off ramps,
and
c. provide on ramps to handle double left turns from Bonita Road.
Because of budget limitations, only two ramps will be modified in the
near future. These will be the ramps on the east side of the
freeway, which CalTrans expects to have completed before the
Christmas shopping season this year. This improvement will have
beneficial impacts to both traffic safety and capacity.
4. If feasible, CalTrans will implement our proposal to install double left
turn lanes for both the northbound and southbound freeway on ramps from
Bonita Road. This will increase the capacity of the interchange by
allowing almost twice as many vehicles to turn onto the ramps in the same
amount of time.
5. The City will be installing a traffic signal at Bonita Road/Bonita Glenn
Drive along with a raised median divider on Bonita Road between the
freeway and Bonita Glen Drive. We have agreed to interconnect this signal
with the signals at the freeway. These improvements are expected to
maintain good traffic flow and improve traffic safety in the area. We
anticipate the signal to be operational in April 1984.
.. ... ...................
Page 3, Item 26
Meeting Date 8/16/83
It is staff's opinion that the above improvements, coupled with the opening of
East "H" Street later this week, should significantly improve traffic flow and
safety along this segment of Bonita Road.
FINANCIAL STATEMENT: Both Caltrans and the County will be completely
funding those improvements identifiable with their agencies. The City will
install the traffic signal at Bonita Road/Bonita Glen Drive, the interconnect
between this signal and the freeway signals and the raised median island from
Bonita Glen Drive to I-805. The estimated cost for this work is between
$45,000 and $57,000 and will be initially funded by private developers as
outlined in Resolution 11053. Ultimately, this funding will be reimbursed to
the private developers through the Traffic Signal Fund.
FISCAL IMPACT: The annual cost to the City to operate and maintain the
traffic signal at Bonita Road/Bonita Glen Drive will be approximately $2,900.
It is anticipated that the City's share for operation and maintenance of the
freeway signals will not change (currently around $5,000 per year) .
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REPORT ON ALTERNATIVE SOLUTIONS
TO SAFETY PROBLEMS ON
NACION AVENUE AND ON
EAST "L" STREET
MARCH 1980
Engineering Department
Advanced Planning and Environmental Division
Prepared byr William Ulirich, William Harshman
(Incorporating information supplied
by City Traffic Engineer; Gary Hansen)
Date : March 3 , 1980
Submitted to City Council: March 11 , 1980
REPORT ON ALTERNATIVE SOLUTIONS TO SAFETY
I_ PROBLEMS ON NACION AVENUE AND
ON EAST " L" STREET
I. BACKGROUND/PURPOSE
On November 6 , 1979 , the City Council considered an
engineering staff report which explored long term solutions
to the existing traffic safety problems on Nacion Avenue
between East " L" Street and East Naples Street . Council
directed staff to "develop cost estimates and determine the
impact on adjacent property of :
a) closing Nacion Avenue to through traffic between
Inkopah and East Moss Streets ,
b) Installing a traffic signal at East " L" Street and
Melrose before Nacion is closed , and
c) rebuilding East " L" Street to provide for a design
speed of 35 MPH.
This report addresses various alternative solutions to the
traffic safety problems on both Nacion Avenue and East " L"
Street . Its purpose is to inform and to facilitate the
decision-making process .
II . RECOMMENDATION
It is recommended that the City Council :
A. Direct the immediate elimination of parking along the
" inside" curb of curves on Nacion Avenue between East
" L" Street and Inkopah Street. (Alternative N-1 )
B. Consider the following projects for inclusion in the
Capital Improvement Program :
1. increase curve radii to minimum of 350 ' , and widen
Nacion Avenue four feet on the easterly side to
achieve residential collector standard width (40
feet) , ( Alternative N-3 ) ;
2. reconstruct East " L" Street between Melrose Avenue
and Nacion Avenue to provide adequate sight
distance (Alternative L-l ) ;
3. install traffic signalization at the intersection
of Melrose Avenue and East " L" Street when traffic
signal criteria are met (Alternative S-1 ) .
J 1'
11
GENERAL DISCUSSION
A. THE PROBLEMS, THEIR ALTERNATIVE SOLUTIONS AND THE
INTERRELATIONSHIP OF SOLUTIONS
1. Street System in the Area .
The area of concern is bounded by East " L" Street ,
East Naples Street , Melrose Avenue , and 1-805 , and
is served by a network of collector , residential
collector , and residential streets . (See Figure
1, Page 3 )
East " L" Street is constructed to collector
standards (64 foot travelway) and serves as one of
the City' s most important streets . It constitutes
a vital link to the rapidly growing El Rancho del
Rey area and provides one of five access points to
the I-805 freeway within Chula Vista .
Nacion Avenue is one of only three " through"
north/south streets in the area between 1-805 and
Hilltop Drive ( "L" Street to Palomar Street) .
Chula Vista ' s street system WEST of Hilltop Drive
is typified by a grid of collector/residential
collector streets on quarter-mile spacing . " There
are proportionately fewer such streets in the area
east of Hilltop Drive . This relative shortage is
compounded by the fact that some of Nacion Avenue
is of less width (36 ' ) than a standard residential
collector street (40 ' ) .
If developed currently, Nacion Avenue would have
to be built to residential collector standards .
Nacion Avenue is located roughly adjacent to the
I-805 freeway and is the most convenient route to
the freeway for many of the residents of the East
" L" St ./Nacion Ave . area . For this reason too ,
it functions as a residential collector despite
its inadequacies .
The general distribution of traffic on the area ' s
more important streets is shown on Figure 1 (Page
3 ) . Average daily traffic (ADT) on the subject
segment of East " L" Street is 17 , 500 and expected
to increase . Nacion Avenue (ADT 4750 ) carries
approximately twice the volume carried by Melrose
Avenue (ADT 2400 ) . These figures reflect the
perceptions of area residents as to shortest ,
safest and/or most convenient routes to a variety
of destinations .
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..... ......... ............ ...
2. East "L" Street .
Flow of traffic along East " L" Street is
imperilled by the existence of a crest vertical
curve between Melrose Ave . and Nacion Ave. which
provides stopping sight distance for a maximum
speed of only 25 MPH. Adjacent segments of East
" L" Street provide stopping sight distances for
speeds of at least 35 MPH. Such inconsistency of
design creates a hazardous situation since it
involves a choice by the motorist to either travel
significantly below the prevailing speed , or
travel in excess of the safe speed provided by the
available sight distance . The majority of drivers
have chosen the latter option .
Certain intersecting streets (Monterey Ct . and
Mission Ave .) are situated just beyond the view of
drivers on East " L" Street as they approach the
critical crest vertical curve . Neither the driver
entering East " L" Street or the driver traveling
on East " L" Street can see the other during a
short , but critical period of time .
The situation is potentially quite hazardous and
we believe should be resolved WHETHER OR NOT
CORRECTIVE ACTION IS TAKEN ON NACION AVENUE.
Action taken to date on East " L Street incluc'.e
installation ( in 1972) of flashing yellow lights
with 25 MPH speed signs at the crest of the hill ,
and restriping (1979 ) so as to eliminate parking
and provide left turn lanes at some locations .
Neither action provides solution to the basic
problem which is inadequate stopping sight
distance .
Other low-cost " solutions" studied in the past
include overhead mirrors and construction of a
median island . Neither offers a wholly viable
answer to the sight distance problem . The raised
median would provide a degree of increased safety
in liriting certain traffic movements . However ,
it would not change the inadequate sight distance
situation on East " L" Street . Such a median would
result in inconvenient access to Monterey Court
and Mission Avenue .
The only truly effective and long-term solution is
to modify the street grade in such manner as to
provide the required stopping sight distance .
Engineering staff has evaluated two such methods -
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by cut only, and by both cut and fill . The
(`. concepts involved are shown in Figures 2 and 3 (on
Pages 6 & 7 ) , respectively. Both alternatives are
considered in detail in the appendix . That method
involving both cut and fill has been selected as
the more economical and practical option to be
considered throughout this report , and is herein
referred to as Alternative L-l .
3. Nacion Avenue .
Nacion Avenue between Inkopah Street and East "L"
Street is characterized by its 36 foot travelway
(which is 4 feet less than the 40 foot travelway
utilized for residential collector streets) ,
relatively steep grades and four relatively sharp
horizontal curves . The adjacent segment south of
Inkopah Street is without curves and has no homes
(and little parking) along its easterly side .
Thus , the driver northbound on Nacion Avenue
encounters abrupt changes in alignment , amount of
side interference and sight distance . Failure to
respond to such changes is probably contributory
to the high number of accidents for northbound
vehicles over the past several years .
Horizontal curves as now constructed along the
subject segment of Nacion Avenue provide a safe
stopping sight distance of only 15 MPH. Speed
surveys show the 85th percentile speed to be about
33 MPH. Most drivers , therefore , manipulate this
segment of Nacion Avenue at unsafe speeds .
The Nacion Avenue situation has proven itself to
be hazardous and it should be resolved WHETHER OR
NOT CORRECTIVE ACTION IS TAKEN ON EAST " L" STREET.
Actions taken to date on Nacion Avenue include
signing , centerline striping , additional street
lighting , reflective markers on centerline , and a
barrier and reflective markers at the curve
between Inkopah Street and East Moss Street .
During the months since those various actions have
been taken the accident rate along the subject
segment of Nacion Avenue has shown a moderate
reduction . Only more time can provide a
dependable gage of their collective effectiveness .
Most of the Nacion Avenue accidents over the years
have involved loss of control and striking a fixed
object . The actions taken to date relate
primarily to that type of accident .
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Residents of property fronting on Nacion Avenue
who must back into traffic perceive the major
problem to be inadequate sight distance . Actions
taken to date have done little to alleviate their
concerns . Prohibition of parking along much of
the curvilinear segment of Nacion Avenue would
increase sight distance by 5 MPH, a significant
but not totally adequate amount . Adequate (30
MPH) sight distance can be obtained through a
combination of widening the street and increasing
the radii of its curves .
Staff investigated four possible "solutions" to
the Nacion Avenue situation :
a . (Alternative N-1 ) : Prohibit parking along
the " inside" of curves on existing street
improvements , _
b . (Alternative N-2 ) : Increase curve radii to
the maximum practical extent within the
existing street right-of-way and prohibit
parking on the " inside" of curves ( see Figure
4 , Page 9 ) .
c . (Alternative N-3 ) : Acquire right-of-way,
increase curve radii to a minimum of 350
feet , widen pavement to residential collector
standard (40 ' ) and prohibit parking on the
" inside" of curves (See Figure 5 , Page 10) .
d . (Alternative N-4 ) : Close Nacion Avenue to
through traffic by permanent modification of
the street improvements and minor right-of--
way acquisition (see Figures 6 and 7 , Pages
11 & 12 ) .
4. Intersection Control at Melrose Avenue and East
• " L" Street .
The existing intersection control at Melrose
Avenue and East " L" Street is a two-way stop on
Melrose Avenue . Studies show that the current
conditions at the intersection are close to but do
not yet satisfy the criteria used by the City of
Chula Vista for the installation of a traffic
signal .
The only viable alternative to the existing two-
way stop is installation of a traffic signal
system at the intersection . This item is
identified as Alternative S-1 .
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5. Interrelationship of Problems Under Certain of the
•
Alternatives .
The traffic problems on East "L" Street and on
Nacion Avenue are seemingly independent of one
another . Each is recognized by Engineering staff
as being sufficiently serious as to require near-
term resolution on its own . In most cases the
alternatives for a given problem could be
constructed without direct impact on other area
problems . For instance , the East "L" Street sight
distance problem could be resolved and yet not
improve the situation on Nacion Avenue .
Conversely, the isolated construction of the
closure of Nacion Avenue to through traffic would
compound the need for resolution of the East "L"
Street problem . The latter "chain-reaction" type
impacts arise relative to only two of the total
number of alternatives :
a . (Alternative N-4 ) : Closure of Nacion Avenue
to through traffic , and
b . (Alternative S-1 ) : Signalization of the
Melrose and East " L" Street intersecti2n .
Closure of Nacion Avenue to through traffic (see
Figure 6 , Page 11) would impose higher traffic
loadings on both Oleander Avenue and Melrose
Avenue south of Telegraph Canyon Road . The
increased traffic on Melrose would easily satisfy
signal warrants at the intersection of Melrose
Avenue and East " L" Street . Realistically, the
situation at that intersection would change so
much as to demand installation of that
signalization . However , signalization of the
Melrose Ave ./East " L" St . intersection without
correcting the East " L" Street sight distance
situation would simply compound the probability of
rear-end collisions for westbound traffic on East
" L" Street . Such traffic now flows with few
interruptions in the area of the East " L" Street
crest vertical curve characterized by inadequate
sight distance . After installation of a signal at
Melrose Ave ./ East " L" St . , westbound vehicles
will tend to slow down or queue for the signal
( especially during peak flow periods) and thus
constitute a great potential for rear--end
collisions .
Thus the closing of Nacion Avenue would compound
the need for signalization at Melrose and East
-13-
" L" , and in turn would compound the need to
improve sight distance on East "L" Street .
Isolated signalization of the intersection of
Melrose Avenue and East "L" Street would have the
same impact on East " L" Street as described above.
Engineering staff has not made a specific
projection , but it is probable that such
signalization would also have the beneficial
effect of reducing the through traffic loading on
Nacion Avenue . Such a reduction would logically
result in a decrease in Nacion Avenue accidents ,
but would NOT correct the inadequate sight
distance situation which exists on Nacion Avenue .
The potential for these chain reaction impacts
must be considered in the decision-making and
schedule preparation process . East "L" Street and
Nacion Avenue are distinct and individual
problems , but solutions to those problems MAY be
interdependent .
NOTE: FOR FURTHER DETAIL CONCERNING THE
VARIOUS ALTERNATIVES STUDIED, PLEASE SEE THE
APPENDIX.
B. COST ESTIMATES
\ EAST " L" STREET
Alt. L-1 (cut & fill) $465 , 000`
NACION AVENUE
Alt. N-1 (prohibit parking) $ 500
Alt . N-2 ( increase radii within R/W, $ 50 , 000
prohibit parking inside of curves)
Alt . N-3 (acquire R/W, increase radii , $195 , 000
widen , prohibit parking inside of curves)
Alt . N-4 (close to through traffic) $ 35 , 000
SIGNAL
Alt . S-1 (signal at Melrose/East " L" ) $ 70 , 000
NOTES :
1. Costs shown are based on January 1980 prices , and
include design , construction , inspection , right-
of-way and contingencies .
-14-
C- 2. Environmental processing costs are expected to be
insignificant for all alternatives EXCEPT the
Nacion Avenue closure alternative.
3. * - Indicates Melrose Ave ./East " L" St . signal
cost must be added .
C. ENVIRONMENTAL REQUIREMENTS
The various alternatives considered for both East " L"
Street and Nacion Avenue have been discused with ' the
City' s Environmental Review Coordinator . All , other
than the Nacion Avenue Closure , would probably be
subject to only the Negative Declaration procedure .
The Nacion Avenue closure alternative would probably
require preparation of a focus E. I. R.
IV. SUMMARY/CONCLUSIONS
Serious traffic problems now exist on East " L" Street and on
Nacion Avenue . Staff has investigated various solutions to
those problems , some of which could be implemented
unilaterally, and some which could be implemented only in
combination with others .
Alternatives studied include :
EAST " L" STREET
Alt. L-1 (Reconstruct East " L" )
NACION AVENUE
Alt . N-1 (Prohibit parking certain areas)
Alt. N-2 (Increase radii within R/W, prohibit parking
certain areas)
Alt . N-3 (Acquire R/W, increase radii , widen , prohibit
parking certain areas)
Alt. N-4 (Closure to through traffic , minor
R/W acquisition)
MELROSE/EAST " L" INTERSECTION
Alt . S-1 (Signal modification)
Note : Alt . N-4 (closure) and Alt . S-1 (signal )
are items impractical of construction unto
themselves and must be undertaken only in
conjunction with other of the alternatives .
We have evaluated various alternatives and combinations of
alternatives . The following Table A is a summary of the
various unilateral and/or combination actions which could be
taken . The table also provides comment on phasing ,
practicality and total estimated cost .
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11■41
We consider both the East "L" Street and Nacion Avenue
problems to be sufficiently serious as to justify prompt and
effective resolution . The Nacion Avenue situation appears
to be the most pressing of the two at this time because of
the higher accident record on that street .
Various actions have already been taken on Nacion Avenue
(centerline , striping , reflective markers , additional
lighting and barrier erection) . These measures have not
been in place long enough to allow a definitive evaluation
of their effectiveness , but in total they appear to have
made Nacion Avenue safer than it was in the past .
There is one additional easily available measure which could
and should be used to provide another incremental increase
in safety for vehicles using Nacion Avenue . That measure is
prohibition of parking (with an attendant loss of 18 or more
parking " spaces" ) on the " inside" of the four curves between
East " L" Street and Inkopah Street . Such an action is not a
complete solution , but it would be quite cost effective and
capable of immediate implementation .
The only Nacion Avenue alternative studied which provides a
realistic sight distance is Alternative N-3 (Item 5 on Table
A - acquire right-of-way, increase curve radii , limit
parking and widen pavement to 40 feet) .
Alternative combinations shown as Items #8 , 9, 10 and 11 on
Table A (Page 17) represent solutions to both East " L"
Street and Nacion Avenue problems . Item #9 utilizes closure
of Nacion Avenue while Items 48 , 10 and 11 involve some form
of upgrading of Nacion Avenue so as to provide more adequate
sight distance .
Item '49 involving closure of Nacion Avenue would
unquestionably reduce traffic volume on that street , but
that improvement would be accomplished at the expense of
dramatically increased volumes along other streets in the
area . Conversely, the upgrading of Nacion Avenue along with
the other features of Item 11 would correct the primary
hazard involved without imposing additional loads upon other
streets . Closure of Nacion Avenue constitutes a shift of
traffic and some of its attendant problems . It would
increase gasoline consumption by approximately 11 , 800
gallons per year . It would NOT cope with the inadequate
sight distance situation on Nacion Avenue .
Items 43 , 10 and 11 all provide some degree of improvement
to Nacion Avenue sight distance without shifting traffic
flows . We consider any of these items preferable to Item
49 .
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As noted in Table A (Page 17) , Items , 7 , 10 and 11 can be
accomplished under one contract (concurrent) or as a phased
program . Availability of funds is likely to play an
important role in reaching that decision .
Engineering staff supports the immediate implementation of
Alt. N-1 (prohibit parking on inside of curves on existing
Nacion Avenue street improvements) because of its low cost
and relative effectiveness in the form of increased sight
distance .
We further support consideration by the City Council of the
following projects for inclusion in the Capital Improvement
Program :
Alt . N-3 (Acquire R/W, increase radii , widen and
prohibit parking on inside of curves on Nacion
Avenue)
Alt . L-1 (Reconstruct East " L" Street)
Alt. S-1 (Signalize Melrose Avenue/East "L" Street)
C
-19--
APPENDIX
to
REPORT ON ALTERNATIVE SOLUTIONS TO SAFETY
PROBLEMS ON NACION AVENUE AND
ON EAST "L" STREET
C
DISCUSSION OF ALTERNATIVES
1. EAST " L" STREET
Two alternatives were investigated relative to the
impaired sight distance on East " L" Street between
Melrose Avenue and Nacion Avenue . Both
alternatives were based on providing a stopping
sight distance to accommodate vehicular speeds to
35 MPH. The two alternatives investigated involve
(1 ) cut only and (2 ) both cut and fill (Alt. L-1 ) .
a . Cut Only (See Figure 2, Page 6 ) .
This alternative requires significant
revisions to private properties and street
improvements in a relatively small area .
Alterations to East " L" Street , Monterey
Court and Mission Avenue would be required .
Five driveways on the cross streets would
have to be altered including three on Mission
Avenue which would require reconstruction to
near-maximum grades .
Four driveways fronting " L" Street wou;.d be
C affected . In three of those cases , the
garage on the property would also have to be
modified (deck lowered) in order to permit
its continued use as a garage . The fourth
driveway would be steepened but would still
provide usable access to the garage .
Garage alterations would be extensive . Two
of the garage floors would have to be lowered
6 feet (305 and 311 "L" Street) and one 3 to
3 . 5 feet (315 "L" Street) . The two most
severe instances may permit development of a
usable room above the new "garage" and
thereby make the modification more palatable
to the property owners .
Extensive retaining walls would be required .
Maximum height of the walls would be 6 feet ,
Location of required retaining walls is shown
on Figure 2, (Page 6 ) . Sight distance for
drivers backing out from the driveways of
305 , 311 , 315 and 319 " L" Street would be
restricted until the rear bumper reached a
position e-:en with the gutter ( worst case) .
To improve sight distance for drivers using
these driveways the retaining wall could be
moved furt:er onto private property (with
property owners permission) .
A- 1
• ,
The "cut only" alternate would also require
0-j reconstruction of a segment of an 8 " sewer
line and some other utilities within the
street reconstruction area .
Total estimated cost for the "cut only"
option is $530 , 000 exclusive of signalization
of Melrose Avenue . This "option" was not
selected for consideration in the report text
because of its higher cost and greater
physical impact as compared to the "cut and
fill" option (Alt. L-I) .
b . Combined Cut and Fill (See Figure 3 , (Page 7 )
(Alt. L-1 )
This alternate requires relatively moderate
revisions to private properties and street
improvements over an area twice as large as
the "cut only" alternative. Under this
concept , adjacent garages would not be
disturbed and depth of cut would be limited
to the amount which would still permit access
by steepening the driveways . Part of the
roadway section would involve cut and part
would involve fill . Residences along ,East
" L" Street which would have steep driveways
`. ` include #305 , 311 and 315.
Cross streets (Melrose , Monterey, Mission and
Nolan) would have to be modified to meet the
revised grade of East " L" Street . Five
driveways from those cross streets would also
have to be changed . Of these , three would
involve work on only the driveway approach in
the public street . The two remaining would
be steepened and would require reconstruction
on private property.
Retaining walls would have to be constructed
in both the cut and fill sections . The
height of these walls would be no greater
than 3 feet . Existing retaining walls would
remain in place . The average height of
retaining walls for this alternative would be
approximately 2 feet .
Although this alternative requires more total
length of " L" Street to be reconstructed than
the " cut only" alternative , the extent of
alteration to adjacent property and side
streets is considerably less . This
alternative would permit more extensive use
A-2
of pavement overlay than the "cut only"
alternative.
There should not be a sight distance problem
for vehicles backing out of modified
driveways since the driver' s eye level is
anticipated to be above the proposed
retaining wall in each case . Again , with the
owners' permission any sight distance
problems which might conceivably develop
could be eliminated by setting the wall
further onto - private property.
2. NACION AVENUE
Four alternatives were investigated relative to
the inadequate sight distance on Nacion Avenue
between East "L" Street and Inkopah Street . Two
of these alternatives involve increasing the
stopping sight distance and one involves physical
closure of Nacion Avenue to through traffic .
Specifically, the alternatives investigated
included :
1. Alt. N-1 , prohibit parking along the " inside
of curves ( no modification of street
improvements) .
2. Alt . N-2 , increase curve radii within
existing right-of-way, prohibit parking on
" inside" of curves .
3. Alt . N-3 , increase curve radii to 350 feet
(min .) acquire right-of-way, widen pavement
to 40 feet and prohibit parking on " inside"
of curves .
4. Alt. N-4 , close Nacion to through traffic by
permanent modification to the street
improvements . (Minor right-of-way
acquisition . )
Most accidents which have occured along the
subject segment of Nacion Avenue since 1974 have
resulted from excessive speed ( 11 of 25) or drunk
driving (7 of 25) . It is important to note that
18 of the reported accidents involved northbound
vehicles ( for which the roadway character changes
from straight to curvilinear) . Increasing the
radius of those curves and/or widening the roadway
will reduce the hazard in driving the road at any
given speed . However , the abrupt change in
( character of the roadway will remain essentially
A-3
• .
the same and will be difficult to traverse by
speeders and/or drunks . NONE of the alternatives
studied , including closure , would safely
accommodate drivers in those categories .
a . ALT. N-1 (Prohibit Parking)
Under this alternative no modifications would
be made to the existing street surface
improvements ( pavement , curb , sidewalk,
driveways) . The action would consist solely
of erecting "No Parking" signs and painting
curbs . Parking would be prohibited along the
" inside" curb of each curve . Sight distance
would thereby be increased so as to be
adequate for a vehicle speed of 20 MPH.
(Current safe speed based on stopping sight
distance is 15 MPH. ) While this alternative
DOES NOT provide adequate sight distance , it
would constitute a valid improvement which
could be implemented immediately and at
insignificant cost .
The following is a summary of the more direct
significant impacts of this alternative :
C 1. Increase safe speed (based on stopping
sight distance) from 15 MPH to 20 MPH.
2. Elimination of on-street parking for 7
properties situated on the " inside of
curves" .
b . ALT. N-2 (Increase curve radii within right-
of-way and prohibit some parking) (See Figure
4 , Page 9 )
This alternative maintains existing street
width (36 ' ) except where horizontal curves
occur . At curves the " inside" curb and
sidewalk would be relocated in such manner as
to provide the maximum possible driving lane
radius within the existing right-of-way.
Under this alternative it would be necessary
to prohibit parking on the " inside" curb of
each curve in order to maximize sight
distance . Existing horizontal sight distance
is adequate for a vehicle speed of only 15
MPH . Increasing the curve radii and
eliminating some parking would provide sight
distance adequate for a vehicle speed of 24
MPH . However , speed surveys taken by staff
show the 85th percentile speed to be about 33
A- 4-
MPH. Thus 85% of the drivers are even now
driving too fast to safely negotiate the
increased radii curves which this alternative
could provide. It is unlikely that the 85th
percentile speed will reduce. In fact,
drivers might actually increase their speed
because of improved sight distance through
the curves .
We do not rccommend this alternative because
the increased sight distance provided is not
commensurate with the cost involved .
The following is a summary of the more
significant direct impacts of this
alternative :
1 . Loss of on-street parking for 7
properties located on the " inside" of
curves .
2. Removal of approximately 11 street
trees .
3. Reconstruction of 4 driveway approaches .
C4. Relocation of 3 utility poles .
c . ALT. N-3 (Increase Radii , acquire right-of-
way, widen , prohibit some parking) (See
Figure 5 , Page 10)
Nacion Avenue is now 36 feet between curbs.
The residential collector standard calls for
a width of 40 feet . Nacion Avenue is in fact
being used as a residential collector . To
adequately serve in that function it should
be widened by 4 feet .
Engineering staff considered widening 2 feet
on each side of the street but eliminated
that option as a viable alternative because
the impact and cost were far in excess of
those to widen 4 feet on one side only. Our
study is therefore based on a non-symmetrical
widening in which curve radii would be
increased to 350 feet . Such design would
provide sight distance adequate for a vehicle
speed of 30 MPH .
Right-of-way acquisition as shown on Figure
5 , Page 10 would total approximately 3, 150
square feet and would involve 9 separate
A-5
ownerships . The following is a summary of
(7 the more significant impacts of this
alternative :
(1 ) Removal of approximately 30 trees;
(2 ) Relocation of 8 utility poles ;
(3 ) Reconstruction of 15 driveway approaches
and at least 4 driveways ;
(4 ) Construction of a retaining wall at 283
Nacion Avenue ;
(5 ) Significant reduction in width of the
existing park way along the entire east
side and certain limited segments on the
west side;
(6 ) Acquisition of 3, 150 square feet of
right-of-way;
(7 ) Elimination of parking in driveway at
977 Nacion Avenue ;
(8 ) Loss of on-street parking spaces .for 7
( properties on the " inside" of curves .
d . ALT. N-4 (Closure of street to through
traffic) (See Figure 6 , Page 11)
Under this alternative a physical revision
would be made to the street improvements so
as to prevent through traffic from using the
curvilinear segment of Nacion Avenue . The
closure could utilize either back-to-back
cul-de-sacs or a cul-de-sac and a knuckle .
The latter appears to be the more practical
solution and so staff' s investigation has
centered on that option .
Closure can generally be accomplished within
the existing right-of-way, but a minor right-
of-way acquisition would be necessary at the
inside of the southwest corner of Nacion
Avenue/Inkopah Street . Right-of-way
acquisition as shown on Figure 6 , Page 11
would total approximately 200 square feet .
Little disturbance of adjacent landscaping or
utilities will be necessary . The remaining
unused street area could be transformed into
a mini-park .
A-6
Of those alternatives involving revision of
�r the Nacion street surface facilities , Alt . N-
2 is the least expensive in direct cost of
those studied . Conversely, it will create
the greatest impact because it will change
traffic circulation throughout the
neighborhood . Traffic volumes , speeds and
safety problems will shift and adjust in the
manner of a chain reaction .
The Traffic Engineering Division has collected vehicle
traffic count and license plate data on Nacion Avenue
in order to estimate the volume and the
origin/destination of the through traffic using this
street . By taking counts at several locations along
Nacion Avenue between East "L" and East Naples Street ,
an estimate of the volume of through traffic was made.
After recording the license plates of vehicles on
Nacion Avenue during several hours during the day, the
address of the registered owner was determined and this
address was assumed to be the origin or the destination
of the vehicle trip.
Traffic volumes (1979 ) on Nacion Avenue and nearby
streets are shown on Figure 1, (Page 13 ) . Of the 4250
vehicles/day on Nacion Avenue just south of East " L"
Street . The Traffic Engineer estimates that
approximately 3400 of these vehicles are through
traffic on Nacion Avenue ( i .e . , are coming from or
destined for an address south of Inkopah Street) .
Figure 1 also shows the breakdown of the addresses of
the through vehicles on Nacion Avenue by area .
Through traffic northbound on Nacion Avenue at East " L"
Street was monitored . It was found that 70 percent
turned right , 28 percent went straight , and 2 percent
turned left . This data showed that practically all of
the northbound through traffic on Nacion Avenue was
destined for points north or east of the intersection
of Nacion Avenue/East " L" Street . (The same conclusion
was made relative to origin of southbound through
traffic . ) The I-805 freeway, Canyon Plaza Shopping
Center , Southwestern College , and Hilltop 'Jr . & Sr .
High Schools were assumed to be major
origin/destination points .
If Nacion Avenue is closed to through traffic , the
Traffic Engineer has proposed that the closure be made
between Moss and Inkopah Streets based on the
following .
( 1 ) This location will minimize the traffic volumes on
Nacion Avenue in the vicinity of the sharp curves
( north of Inkopah Street) .
A-7
K .
•
(2) This location will minimize the increase
necessitated by the street closure in vehicle
miles traveled for residents of the adjacent area .
(3 ) The existing arrangement of lots and street
improvements facilitate the physical closing of
Nacion Avenue .
The following assumptions were made regarding trip
generation and trip characteristics of the through
traffic on Nacion Avenue , should this street be closed :
(1 ) Trip generation or trip destination would not
change significantly.
(2 ) Motorists would take the alternate route which
minimized the increase in vehicle miles traveled .
(3 ) Motorists would avoid congested areas and would
prefer to gain access to or cross East " L" Street/
Telegraph Canyon Road at an intersection which had
a traffic signal .
There are two other north-south "collector" streets in
the area which could absorb rerouted through traffic
from Nacion Avenue . Based on data collected and the
C " preceding assumptions , the 3400 through trips/day were
assigned to Melrose Avenue (2400 trips) and Oleander
Avenue (1000 trips) . (See Figure 7 , Page 12 ) .
The existing traffic conditions on Melrose Avenue and
on Oleander Avenue were examined in order to assess the
impact of the additional traffic rerouted from Nacion
Avenue .
The closure of Nacion Avenue would increase the traffic
volume on Oleander Avenue south of Telegraph Canyon
Road from 5900 to 5900 vehicles/day. This is below the
practical capacity ( level of service " E" ) (9-12 , 000
vehicles/day) for such a two lane collector street .
Another important consideration is the impact of
increased traffic upon the intersection of Telegraph
Canyon Road/Oleander Avenue . The existing traffic
signal at that intersection facilitates access to the
arterial street from Oleander Avenue , The additional
traffic on Oleander Avenue could be handled by this
intersection without a noticeable increase in
congestion .
The traffic volume on Melrose Avenue south of East " L"
Street would increase from 2400 to 4300 vehicles/day.
This is below the design capacity of Melrose Avenue ,
A-8
but we expect significant delays and increased traffic
accident hazards at East "L" Street/Melrose Avenue .
That intersection is presently controlled by a two way
stop on Melrose Avenue .
This intersection is annually evaluated against
CALTRANS signal warrants to determine if a traffic
signal is justified . A summary of the analysis
recently completed follows :
(1 ) The number of hours/day that the interruption of
continuous traffic warrant is met is five (8 hours
needed to satisfy warrant) . An increase of 20
vehicles/hour on Melrose Avenue for the additional
three hours will result in this intersection
satisfying this warrant for signal installation .
(2 ) 'There were four accidents in the period September
78-August 79 which were susceptable to correction
by a traffic signal ( right angle accidents) . The
accident warrant is satisfied when there are five
such accidents in a 12-month period .
As the preceding indicates , the existing conditions at
the intersection of East " L" Street/Melrose Avenue are
close to satisfying the criteria for the installation
C of a traffic signal . The rerouting of 2400
vehicles/day from Nacion Avenue will result in traffic
conditions on Melrose Avenue which more than satisfy
the signal warrants at East " L" Street .
It has been suggested that Nacion Avenue be closed
temporarily to assess the impacts on the circulation
system . It is strongly recommended that this scheme
NOT be attempted based on the following :
(1 ) On a temporary basis , it is not possible to
install a traffic signal at East " L"
Street/Mel rose Avenue .
( 2 ) The increase in traffic on Melrose Avenue at East
" L" Street will result in increased delay on the
minor street and increased driver
impatience/frustration . The latter may lead to an
increase in the number of intersection accidents
because impatient motorists on Melrose Avenue may
start selecting inadequate gaps in the traffic on
East " L" Street in which to attempt to gain access
to or cross the arterial street .
( 3 ) The conditions at East " L" Street/Mel rose Avenue
will force some motorists to use more circuitous
routes that would not be necessary if there were a
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traffic signal at the intersection . This will
(7-3 result in driver confusion , an unnecessary
expenditure of non-recoverable fuel by increasing
the Vehicle Miles Traveled (VMT) , and increased
traffic on local streets (streets not designed to
carry through traffic) .
Certain environmental impacts will also result from
closure of Nacion Avenue . Those impacts are :
(1 ) Noise
(2) Energy consumption
(3 ) Air quality
Noise impacts will occur on Melrose Avenue , Oleander
Avenue and other local streets upon which increased
traffic flow occurs . (See Figure 7 on Page 12 for
post-closure traffic volume projections .)
The projected increase in traffic on Melrose Avenue
would increase noise levels along that street by
3db (A) . Oleander Avenue noise would increase in the
range of 0. 5 to 1 . 0db (A) . Noise increases on other
local streets would be in the range of 0. 5 to l . :,db (A) .
While a 3db (A) increase will be discernable to local
residents , lesser noise increases will not.
Vehicular energy consumption will generally increase
directly with the increase in vehicle miles traveled
Closure of Nacion Avenue would increase area vehicle
miles traveled approximately 550 miles per day. Using
a consumption rate of 17 MPG , the extra gasoline
consumption per day would be 32 gallons or about 11, 800
gallons per year .
Any increase in vehicle miles traveled will generate a
proportionate increase in air pollutants . Such
increase in this instance would be insignificant .
A-l0