HomeMy WebLinkAbout1987-03-02; Traffic Safety Commission; ; The Traffic Safety Coordinating Committee recommends that the request for an all-way stop at the intersection of Alga Road and Corinita Street be deniedCITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
COMMISSION REPORT OF: March 2, 1987 ITEM N0.6-8
LOCATION: Intersection of Alga Road and Corintia Street
INITIATED BY: Tom Erwin, Traffic Safety Commissioner
BACKGROUND:
Commiss i oner Erwin, at the February 2, 1987 meeting of the
Traffic Safety Commission, asked staff to investigate the
need for an all-way stop at the above referenced intersection
until the time that the traffic signal is installed. The
Traffic Safety Commission, by a 3-2 vote on November 3, 1986,
recommended to the City Council that a traffic signal be
installed.
DATA:
On December 2, 1986, the Carlsbad City Council approved
Resolution No. 8890 authorizing the traffic signal and
appropriating funds for the design and installation of the
signal at the intersection of Alga Road and Corintia Street.
At this time, the traffic signal is being designed by a
consulting traffic engineer and it is anticipated that the
signal will be operational no later than September 1, 1987.
Generally, an all-way stop is considered when traffic volumes
are approximately equal on each leg of the intersection. At
this location, volumes are disproportionately greater on Alga
Road then Corintia Street.
A traffic count was taken in September 1986 at this intersec-
tion (data sheets attached). There have been two (2)
reported accidents at the intersection during the past twenty
(20) months. Warrants for an all-way stop are attached.
Existing volumes, accident record and conditions at this
location does not warrant an all-way stop for the
intersection.
6-8-1
TRAFFIC SA FE TY COM MISSION
COMMISSION RE PORT OF: March 2 , 1987
Continued
RECOMMENDA TION:
ITEM NO.6-B
The Traffic Safety Co ordinating Com mittee recommends that the
request for an all-way stop at the intersection of Alga Road
and Cor i ntia Street be denied.
NECESSARY COUNCIL ACTION:
City Co uncil approval of an a ll-way stop will be necessary ,
if recommended .
6-B-2
Traffic Manual TRAFFIC SIGNALS AND LIGHTING 9-1
12-1979
CHAPTER 9
TRAFFIC SIGNALS AND LIGHTING
Traffic Signals-Basic Information and Warrants 9~1
9-01.1 lntrodudion
Traffic signals are electrically powered traffic con-
trol devices which alternately direct traffic to stop
and proceed at highway and street intersections.
Their purpose is the orderly assignment of right of
way to the various traffic movements.
When justified and properly designed, a traffic sig-
nal installation may achieve one or more of the fol-
lowing:
l. Reduce the frequency of certain types of acci-
dents; especially the right-angle type;
2. Effect orderly traffic movement;
3. By proper coordination, the continuous flow of
a. platoon of traffic at a definite speed along a
given route;
4. Allow other vehicles and pedestrians to cross a
heavy traffic stream; and
5. Control traffic more economically than by man-
ual methods.
Unjustified, ill-designed, improperly-operated, or
poorly maintained traffic signals may cause:
1. Increased accident frequency,
2. Excessive delay,
3. Disregard of signal indications, and
4. Circuitous travel by alternate routes.
Contrary to common belief, traffic signals do not
always increase safety and reduce delay. Experience
shows that the number of right-angle collisions may
decrease after the installation of signals, but the num-
ber of rear-end collisions will increase in many in-
stances. The installation of signals may increase over-
all delay and reduce intersection capacity.
Consequently, it is of the utmost importance that the
consideration of a signal installation and the selection
of e9uipment be preceded by a thorough study of
traffic and roadway conditions made by an engineer
expe.rienced and trained in this field. Equally impor-
tant 1s the need for checking the efficiency of a traffic
signal in operation. This determines the degree to
which the type of installation and the timing pro-
gram meets the requirements of traffic.
9-01 .2 Warrants
The warrants for the installation of traffic signals
are based on those stated in the Manual on Uniform
Traffic Control Devices. These warrants apply to
both pre-timed and traffic-actuated traffic signals.
When the 85-percentile speed of major street traf-
fic exceeds 40 miles per hour, or when the intersec-
tion lies within the built-up area oi an isolated com-
munity having a population less than 10,000, the
location is considered rural. All other areas are con-
sidered urban. Since the installation of traffic signals
may increase certain types of collisions, the decision
to install signals should not be based solely upon war-
ran ts. Consideration should also be given to such fac-
tors as delay, congestion, approach conditions, driver
confusion and additional evidence of need for right
of way assignment above that which could be pro-
vided by stop signs.
The installation of traffic signals should be consid-
ered if one or more of the warrants listed below are
met:
Warrant 1-Minimum Vehicular Volume.
Warrant 2 -Interruption of Continuous Traffic.
Warrant 3-Minimum Pedestrian Volume.
Warrant 4 -School Crossings.
Warrant 5 -Progressive Movement.
Warrant 6 -Accident Experience.
Warrant 7 -Systems.
Warrant 8 -Combination of Warrants.
9-01.3 Warrant 1 -M inimum Vehicular Volume
The minimum vehicular volume warrant is intend-
ed for application where the volume of intersecting
traffic is the principal reason for consideration of sig-
nal installation. The warrant is satisfied when for
each of any 8 hours of an average day the traffic
volumes given in the table below exist on the major
street and on the higher-volume minor street ap-
proach to the intersection.
'.'Jumher of lan.:s for
moving traffic on
c:ac h approach
Vehi cles per
hour on maior
street (to tal
o f both
a pproaches)
\'eh,cles per
hour on higher-
volume minor-
stre et approach
(one direction
un\y)
(\1 in,mum Requirements)
"-1 ajor Street \1inor Stree t ~ Rural l :rban Rura l
I -------I -------500 350 l SO 105
2 or more --I -------600 420 150 105
2 or more - -2 or more --600 420 200 140
l -------2ormore--500 350 200 140
9-2 TRAFFIC SIGNALS AND LIGHTING Traffic Manual
12-1979
The major street and the minor street volumes are
for the same 8 hours. During those 8 hours the direc-
tion of higher volume on the minor street may be on
one approach during some hours and on the opposite
approach during other hours.
Left turn movements from the major street may
be included with minor street volumes if a separate
signal phase is to be provided for the left turn move-
ment. The left turn volume in the highest direction
may be added to the minor street volume on the
highest approach and the major street volume should
be reduced by this amount.
9-01.4 Warrant 2 -Interruption of Continuous Traffic
The interruption of continuous traffic warrant ap-
plies to operatL"lg conditions where the traffic vol-
ume on a major street is so heavy that traffic on a
minor intersecting street suffers excessive delay or
hazard in entering or crossing the major street. The
warrant is satisfied when for each of any 8 hours of
an average day the traffic volumes given in the table
below exist on the major street and on the higher-
volume minor street approach to the intersection,
and the signal installation will not seriously disrupt
progressive traffic flow.
Number of lanes for
moving traffic on
each approach
Vehic les per
hour on major
street (total
of both
approaches)
Vehicles per
hour on higher-
volume minor-
street approach
(one direction
only)
(Minimum Requirements)
Major Street Minor Street Urban Rural Urban ~
1-------1-------
2 or more --1 - --- - - -
2 or more --2 or more·•
l - - --- --2 or more - -
750
900
900
750
525
630
630
525
75
75
100
100
53
53
70
70
The major street and minor street volumes are for
the same 8 hours. During those 8 hours the direction
of higher volume on the minor street may be on one
approach during some hours and on the opposite
approach during other hours.
Left turn movements from the major street may
be included with minor street volumes if a separate
signal phase is to be provided for left turn move-
ment. The left turn volwne in the highest direction
may be added to the minor street volume on the
highest approach and the major street volume should
be reduced by this amount.
9-01.5 Warrant 3-Minimum Pedestrian Volume
The minimum pedestrian volwne warrant is satis-
fied when for each of any 8 hours of an average day
the following traffic volumes exist:
1. On the major street 600-Urban, 420-Rural or
more vehicles per hour enter the intersection
(total of both approaches): or 1,000-Urban, 700
-Rural or more vehicles per hour (total of both
approaches) enter the intersection on the ma-
jor street wl-iere there is a raised median island
four feet or more in width; and
2. During the same 8 hours as in paragraph l.,
there are 150-Urban, 105-Rural or more pede-
strians per hour on the highest volume cross-
walk crossing the major street.
A signal installed under this warrant at an isolated
intersection should be of the traffic-actuated type
with push buttons for pedestrians crossing the main
street. If such a signal is installed at an intersection
within a signal system, it should be equipped and
operated to provide proper coordination.
Signals installed according to this warrant shall be
equipped with pedestrian indications conforming to
requirements set forth in other sections of this Man-
ual.
Signals may be installed at nonintersection loca-
tions (Mid-block) provided the requirements of this
warrant are met, and provided that the related cross-
walk is not closer than 150 feet to another established
crosswalk. Curbside parking should be prohibited for
a minimum of 100 feet in advance of and 20 feet
beyond the crosswalk. Phasing, coordination and in-
stallation must conform to standards set forth in this
Manual. Special attention should be given to the sig-
nal head placement and the signs and markings used
at nonintersection locations to be sure drivers are
aware of this special application.
9-41.6 Warrant 4-School Crossings
See Chapter 10.
9-41.7 Warrant 5-Progre11lve Movement
The progressive movement warrant is satisfied
when one of the following is true:
l. On a one-way street or on a street which pre-
ponderantly has unidirectional traffic signifi-
cance, adjacent signals are so far apart that the
necessary degree of platooning and speed con-
trol of vehicles would otherwise be lost or,
2. On a two-way street, where adjacent signals do
not provide the necessary degree of platooning
and speed control and the proposed and adja-
cent signals could constitute a progressive signal
system.
The installation of a signal according to this war-
rant should be based on the 85-percentile speed un-
less an engineering study indicates that another
speed is more desirable.
The installation of a signal according to this war-
Traffic Manual TRAFFIC SIGNALS AND LIGHTING 9-3
rant should not be considered where the resultant
signal spacing would be less than 1,000 feet.
9-41.1 Warrant 6-Accident Experience
The accident-experience warrant is satisfied
when:
1. Adequate trial of less restrictive remedies with
satisfactory observance and enforcement has
failed to reduce the accident frequency; and
2. Five or more reported accidents of types sus•
ceptible of correction by traffic signal control
have occurred within a 12-month period, each
accident involving personal -injury or property
damage to an apparent extent of $200 or more;
and
3. There exists a volume of vehicular and pedes-
trian traffic not less than 80 percent of the re-
quirements specified in the minimum vehicular
-volume warrant, the interruption of continu-
ous traffic warrant, or the minimum pedestrian
-volume warrant; and
4. The signal installation will not seriously disrupt
progressive traffic flow.
9-41.9 Warrant 7 -Systems Warrant
A traffic signal installation at some intersections
may be warranted to encourage concentration and
organization of traffic flow networks. The systems
warrant is applicable when the common intersection
of two or more major routes has a total existing, or
immediately projected, entering volume of at least
800 vehicles during the peak hour of a typical week-
12-1979
day, or each of any five hours of a Saturday and /or
Sunday.
A major route as used in the above warrant has one
or more of the following characteristics:
1. It is part of the street or highway system that
serves as the principal network for through traf-
fic flow;
2. It connects areas of principal traffic generation;
3. It includes rural or suburban highways outside
of, entering or traversing a city;
4. It has surface street freeway or expressway
ramp terminals;
5. It appears as a major route on an official plan
such as a major street plan in an urban area
traffic and transportation study.
9-01.10 Warrant 8-Combination of Warrants
In exceptional cases, signals occasionally may be
justified where no single warrant is satisfied but
where any two of Warrants 1, 2 and 3 are satisfied to
the extent of 80 percent or more of the stated numer-
ical values for each of any 8 hours of an average day.
9-41.11 Periodic Traffic Signal Studies
To maintain the desirable operation of existing
traffic signals, it is necessary to periodically conduct
engineering studies to ensure that t~e des~red ope~a-
tion is realized. In particular, engmeenng studies
should determine whether the installation continues
to be justified and that the signal timing in use meets
the current traffic requirements.
,·. •.· TRAFF! C COUNT A SHEET TS# __ _
Street(s)
Count Date~kt./ /;,;lo '=0/4:sl~ I l
Location: On /l l7A
Data Reduction by M'J2 Date ~ &
7
/Ec.
(btwn/at) C:04/('vZ?<"'f (and) :?A-::1@ /7/112¢
Day/Direction
Time Period a//4,;3 ,m~B
0000-0100 )0
0100-0200 z._
02 00-0300 7
0300-0400 &
0400-0500 )0
0500-0600 ?0
0600-0700 173
0700-0800 Z"77
0800-0900 7_.0~
0900-1000 lCP3
1000-1100 ~
1100-1200 /42..,
1200-1300 iz..q
1300-1400 170
1400-1500 l0Z.
1500-1600 I &Z-
1600-1700 /6(p
1700-1800 17~
1800-1900 J;:, z_
1900-2000 f?t:f '
2000-2100 qg
2100-2200 GO
2200-2300 27
2300-2400 17
TOTAL(S) l,uz.4 C/O!P
PE AK H0UR(S)
PE AK FL0W(S)
Spechl conditions or remarks: __________________ _
Af?C === Z? 3~
, .. .. TRAFFIC COUNT D1 SHEET TS# __ _
Street(s)
Cou nt Date 'i:-/.5-z¼ to q-/u-f,t,
Loc ation: On_.._4.,,__,,_.~'9lo<~c;i;;-----
Time Period ~ ~e,
0000-0100 7-7
0100-0200 lo
020 0-0300 s
0300-0400 Lt-
0400-0500 3
0500 -0600 4
0600-0700 C,
0700-0800 q.7
0800 -0900 l-Z..\
0900 -1000 l 7-t,
1000-1100 l -z._ c:::_,;,
1100-1200 1-Z.~
1200-1300 \ -z. 7
1300 -1400 l -"3 t,
1400-1500 17"3
1500-1600 Z.lt,
1600-1700 270
1700 -1800 3~0
1800 -1900 31-Z...
1900-2000 1r=:;;,7 I
2000-2100 loo,
2100-2200 \03
2200-2300 (,~
2300 -2400 37
TOTAL(S) -z,og~ C/~O
PEAK H0UR(S)
PEAK FL0W(S)
Data Reduction by Mf t.z
(btwn/at) ?~Jt/,,(/17,,4
Day/Direction
Date 9-/e, -ex-,,
( a n d ) LJ "i!;-,,,4~ •
-
Special conditions or remarks: ___________________ _
A[::rr ==--z:..) ~ £B z3
TRAFFIC COUNT SHEET TS# ---
Street ( s) .
Count Da.te 9-)z(¼to i /1.,-St,.
Location: On . ~ M&& ldMZ..-4
Data Reduction by M;?S Date 9-u,-.$::;
(btwn/at) A L9tA (and)~ L-c::..,~....-~
Day/Direction
Ti me Period ~~ ~
0000-0100 3
0100-0200 0
0200-0300 c..
0300-0400 l
0400-0500 ~
0500-0600 \-Z-
0600-0700 {pf
0700-0800 \S\
0800-0900 \ \0
0900-1000 7~
1000-1100 7~
1100-1200 to-i-
1200-1300 IP7
1300-1400 ~:;
1400-1500 • 105
1500-1600 @I
1600-1700 (,7
1700-1800 74
1800-1900 ~~
1900-2000 42-I
2000-2100 Z-\
2100-2200 Z-Z,
2200-2300 14
2300-2400 10
T0TAL(S) 7:3\ s,17
PE AK H0UR(S)
PE AK FL0W(S)
Sp ecial conditions or remarks: ___________________ _
A-ol -== ,, -z... 4 e,
•'. , ..
•.•. I
TRAFFIC COUNT~--A SHEET .
TS# ---
Street(s)
Count Da te4t~ to -Z-~ -tffe&
Location: On CLZ4aal4:
Data Reduction by o/$,, Date 9f /~-c3:::c
(btwn/at) A~A (and) .5__..---.#a:> L,,.
Day /Direction
Time Period ~P-, -r~
0000-0100 3
0100-0200 0
0200-0300 0
0300-0400 ?
0400-0500 0
0500-0600 ~
06 00-0700 Ltq-
0700-0800 \-Z,-Z-
0800-0900 £:,CJ
0900-1000 &O\
1000-1100 ?~
1100-1200 s,-;
1200-1300 3~
1300-1400 44
1400-1500 ~~
1500-1600 01 Z,
1600 -1700 qe,
1700-1800 4C\
1800-1900 ""3~ .
1900-2000 2.~ I
2000-2100 z.o
2100-2200 \0
2200-2300 1-Z-
2300-2400 C,
T0TAL(S) ~4 3~7
PEAK HOUR(S)
PEAK FL0W(S)
Special conditions or remarks: ___________________ _
ADT -:::::.. ~ I
POLICY:
Rl
The Rl sign shall be used on public roads where
a stop is required. Stop signs shall be erected on both
the left and right side of one-way roadways which are
30 feet or more in width. Stop signs shall not be installed
at signalized intersections. Conditions warranting
STOP signs are:
1. On the less important road at its intersection
with a main road where application of the nor-
mal right of way rule is unduly hazardous as
evidenced by accidents susceptible of correc-
tion by STOP signs.
2. On a county road or city street at its intersec-
tions with a state highway.
3. At the intersection of two main highways. The
highway traffic to be stopped depends on ap-
proach speeds, volumes, and turning move-
ments.
4. On a street entering a legally established
through highway or street.
5. On a minor street where the safe approach
speed to the intersection is less than 10 miles per
hour.
A STOP sign is not a "cure-all" and is not a substi-
tute for other traffic control devices. Many times the
need for a STOP sign can be eliminated if the sight
distance is increased by removing obstructions.
The installation of STOP signs at locations where
they are unexpected or where approach speeds are
high should be avoided if possible because they may
increase accidents. However, if there is no alterna-
tive to a STOP sign, then an advance Code Wl7
STOP AHEAD sign and appropriate pavement
markings should be placed in conjunction with it.
Publicity through the radio and press is highly de-
sirable when STOP signs are installed and especially
when it is necessary to change their location.
Any of the following conditions may warrant a
four-way stop sign installation:
1. Where traffic signals are warranted and the
need is urgent, the four-way stop is an interim
measure that can be installed quickly to control
traffic while arrangements are being made for
the signal installation.
2. An accident problem, as indicated by five or
more reported accidents of a type susceptible of
correction by a four-way stop installation in a
12-month period. Types of accidents susceptible
of correction include right angle and left tum
collisions.
3. Minimum volume warrant:
a. The total vehicular volume entering the in-
tersection from all approaches must average
at least 500 vehicles per hour for any eight
hours of an average day, and
b. The combined vehicular and pedestrian vol-
ume from the minor street or highway must
average at least 200 units per hour for the
same eight hours with an average delay to
minor street vehicular traffic of at least 30
seconds per vehicle during the maximum
hour.
c. When the 85-percentile approach speed of
the major street traffic exceeds 40 miles per
hour, the minimum vehicular volume war-
rant is 70 percent of the above requirements.
A four-way stop sign installation is a useful traffic
control measure when other available means of con-
trol are not adequate. It should not be used unless the
volume of traffic on the intersecting roads is about
equal and is undesirable at low-volume intersections,
When STOP signs are placed on all entering legs
of an intersection, each STOP sign may be supple-
mented by a separate plate mounted below it with
the message "3-WAY", "4-WAY", etc. The supple-
mental plate shall have white letters on a red back-
ground.
The 18 .. x18 .. size is for use only on bicycle trails
where bicyclists are required to stop. If the sign applies
to motorists and bicyclists, the standard size stop sign
shall be used.
The bike 18 .. x18" size has be-.: added. The sign
format has been changed to agree with the federal
format Please note the minor change in border width
for the 24", 30", 36" and 48" sizes.
u U L Li 0 I U 11 U UHJ I\}\ II,
CITY 0~ CARLSBAD
TRA FF IC ENGIN ~ERIN G SE C.1 1UN
l' I A I TOTAL ,,o,
/965 I ~3 \ \ /906 2
~ ~ VI
A-._L~~
<l
/
~
),
~
VOL MOVING AH£A0
w ► V£H. eACIIING UI'
----... PEOESTRIAH
TRAIN
c::::::> PARK(O V(HlCL.(
□ F'IX£0 OI JECT
0 PROPERTY 0AMAG£ ONl.T
® INJURY ACCIOClfl' • FAT.ll. ACCIOEMT
HL.9 4 N-·• _; (i Ca/?J/J1!4
1-0-,-,.-.,,-.. ---.----T"----,-
IT m...1-:, ,1110a
_OAf l _t ,/3•.&, _
NO. ACCIDENTS SY TYPE
04.W.AG ( I JIII JU I T ,Ar Al \IOM f OA t ll WI T
\ a 11 \ 0 0
J
N
~lo &vAV/
\{': ~ ~ N
tt\ . -
~ ~ ~ [()
f' ..
'-S 2
~ \) I \l'·
\j'\ j ~
K a o..~ \j)
~ ~
\;.: ~ >~
~ 'N
~ N
~N ~ ['
LEGEND CONST CONSTRUC710N !ONE ~..-Of'O 0"1VEPI P'><TSJC).l. DEFECT H(AO•ON ov OUECTlVE VEHICL!
H£.l0•0H S10£S-,,,IP( ES EXCE SS S?~~O
--..,.;~ RE.t.PI ENO ,re F'Ol.L.OWl"G ro e CL.CSE
H80 HAO SEE!'! ORJN •l"Q OVEPIT.lKINO SlO(SWll'l! H•PI HIT ANO "UN ~l RIGHT ANGL.( ll.C IMPROPER l -"•£ CHANCE
u ••'!OACH T\JRN IP IMPROPER ?&SS INO ~ IT IWPAOP(PI TURN --:i OV(Rf.U INO TUflN INAfT INAT'T(NflCi; _.
~-OUT a, CONTROl. .,.;c I.IOTORCTC!..! -o u-V(HIC\.( TURN(O OV(PI ,.s, """ STCP SIGN OR SIGNAl.
51'" STOPPCO :" $LOWING n)R •~ccs TRIAI•
VO VISl!!ll.llT :Rs rRu~ ~co
VRW VIOL .A Tr~ ::31r-." r ,.,,, ...